CA1094836A - Heat pumps - Google Patents
Heat pumpsInfo
- Publication number
- CA1094836A CA1094836A CA328,862A CA328862A CA1094836A CA 1094836 A CA1094836 A CA 1094836A CA 328862 A CA328862 A CA 328862A CA 1094836 A CA1094836 A CA 1094836A
- Authority
- CA
- Canada
- Prior art keywords
- motor
- heat pump
- compressor
- evaporator
- condenser
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/025—Motor control arrangements
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
- H02P23/24—Controlling the direction, e.g. clockwise or counterclockwise
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
- F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
- F25B2313/0271—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means the compressor allows rotation in reverse direction
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/025—Compressor control by controlling speed
- F25B2600/0253—Compressor control by controlling speed with variable speed
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Inverter Devices (AREA)
- Control Of Ac Motors In General (AREA)
- Control Of Direct Current Motors (AREA)
- Air-Conditioning For Vehicles (AREA)
- Supply And Distribution Of Alternating Current (AREA)
- Compression-Type Refrigeration Machines With Reversible Cycles (AREA)
- Air Conditioning Control Device (AREA)
- Control Of Multiple Motors (AREA)
Abstract
ABSTRACT
A heat pump adaptable for air conditioning or refrigeration use and having a compressor driven by a polyphase electric induction motor, the heat transfer capacity and direction being controllable by controlling the speed and direction of the motor using control equipment to sequentially switch a DC power supply, Both the frequency and effective average phase voltage may be varied to suit the load.
A heat pump adaptable for air conditioning or refrigeration use and having a compressor driven by a polyphase electric induction motor, the heat transfer capacity and direction being controllable by controlling the speed and direction of the motor using control equipment to sequentially switch a DC power supply, Both the frequency and effective average phase voltage may be varied to suit the load.
Description
~ t~ ~ 6 The present invention relates to heat purnps and to control sys-tems for polyphase motors, and, in particular, the present invention relates to a heat pump suitable for use as an automotive air condi-tioning unit and to a control system for a polyphase mo-tor used to power -the heat pump.
In conven-tional automotive air conditioning systems, ' the compressor is driven directly from the motor vehicle engine and thereforè the speed of the compressor is dependent directly upon the speed of the motor vehicle engine. Accordingly regulation of tempera-ture must be brought about by means other than the speed of the compressor. However, in the present invention, temperature regulation is brought about directly by regulatiny the speed of the motor driving the compresso~. In' the preferred embodiment relating to automotive air condition-ing, a relatively low cos-t induction motor is used to drive the compressor and a control system is provided which permits the induction motor to be powered from the vehicle battery via a control system which permits the speed of the induction motor to be controlled and, hence, the temperature of the lnterior of the motor vehicle.
According to one aspect of the present invention there is disclosed a heat pump comprising an evaporator, a ' condenser, a pressure control device connected between the outlet from said condenser and the inlet to said evaporator, a compressor connected b'etween the outlet of said e~aporator and the inlet to said condenser, an electr'ic motor arranged to drive said compressor and a control system for said motor arranyed to enable the speed o;E said motor to be controlled as desired to adjust the amount of heat transferred from said evaporator to said condenser in use.
, ~ ccordiny to another aspect of the present inVention there is disclosed a control system for a polyphase motor havinq one winding per phase and being eneryised from a DC
supply, said control system comprising a pair of electrically operable switches for each phase of said motorr one switch of each pair being operative to connect the correspondin~ windiny of said motor to one terminal oE said DC supply and the other switch of each pair being operative to connect said correspond-ing winding to the other terminal of said DC supply; se~uenciny means connected to said switches to operate the switches of each pair alternatively and to simultaneously ope;rate one switch of every pair in sequence; and rate means connected to said sequencing means to control the rate o~ operation of said .
sequencing means whereby the rate of oneratio,n of said se~uencin-means controls the speed of operation of said polyphase motor, One embodiment of the ~resent invention will now be described with reference to the drawings in ~hich Fig, 1 is a diagrammatic perspective view of a heat pump system according to the invention;
Fig. 2 is a cross-sectional diagrammatic view of the sealed unit used in the heat pump shown in Fig. l;
Fig. 3 is an e~ploded perspective vie~ of the com-ponents of the motor and pump lncorporated within the sealed unit shown in Figure 2;
Figs. ~A - ~H are sequential cross-sectional views of the imneller section of the pump shown in Fig~ 3 at different stages in the pumping cycle.
Fiy. 5 is a block diayram of the preferred embodiment of the control system;
30 , Fiy. 6 is a circuit diagram of the oscillator and 5 - 3 ~
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volt logic power supply;
Fig. 7 is a circuit diagram of the master clock, switch controls and phase sequencer, Fig. 8 is a circuit diagram of the phase controller;
Fig. 9 is a circuit diagram of the main switch, and Fig. 10 is a yraph of the phase voltages applied to the induction motor as a function of time, In the preferred form of the invention a heat pump is constructed as an au-tomotive air-conditioning system although it will be appreciated that the invention may be equally well applied to a large number of heat pump applications.
Referring to Figure 1 the heat pump comprises a con-denser 101 which would normally be mounted towards the front of ; the vehicle, and whlch may be assisted by a fan 102 to draw cooling air through the condenser. An evaporator 103 is pro-vided, mounted within the vehicle and fans or blowers 104 may also be provided to force air through the evaporator 103 for the cooling of the interior of the vehicle. The evaporator and condenser are connected by a conduit 105 in which is incorpor-ated two unidirectional refrigerant limiters 106 and a receiver-drier 107. The refrigerant limiters act as expension valves, each in con~unction with a non-return valve orientated in opposite directions so that only one refrigerant li~iter is in operation at any one time. In the preferred form of the invent-ion the refrigerant limiters are in fact simple non-return valves arranged to have a predetermined amount of"leakage" in the normally closed direction. They therefore achieve substant-; ially unrestricted flo~7 in one direction and restricted flo~
against a predeterm1ned resistance in the opposite direction - 30 The air-conditioning unit is reversible as will be described :, -~ - 4 -.
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hereinafter so that in use as a heat pump the oppositely orientated refrigerant limiter comes into use to control the pressure distribution in the system.
The evaporator 101 and condenser 103 are further linked by a conduit 108 in which is mounted a compressor 109 driven by a motor 110. The motor is preferably provided in ` the form o~ an electric induction motor and the motor and com-pressor are preferably sealed together as a sealed unit within a casing 113. Electric power is supplied to the motor from an automotive battery B14 by way of a controller 112 which will be described in detail below.
When the system is used for cooling the interior of the automobile, heat is pumped using a suitable working fluid in the sy.stem, from the evaporator 103 to the condenser 101 where it is discharged to the atmosphere by the motion of ambient air through the condenser assisted, if necessary, by th~ fan 102. When it is desired to heat the interior of the automobile, the motor 110 is reversed by suitable switching in the control system 112, so that heat is then pumped from the condenser 101 which now acts as an evaporator to the evaporator 103, now acting as a condenser. In this reverse cycle, the oppositely orientated refrigerant limiter 106 comes into operation to giye pressure control in the desired direction.
The use of two refrigerant lim;ters, with non-return valves, acting as a by-pass, allows the refrigerant ~orking fluid to be bi directionally controlled by the operation of the sealed unit - comprising the compressor 109 and the motor 110. A dixect curxent is supplied by the bat~ery B14 to the control unit 112 which conyerts the current to alternating current for use by 3Q the sealed unit induction motor 110, The motor 110 drives the :, , ~ . , ., ' ' .
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compressor 109 in a direction which determines the function of the heat exchangers 101 and 103 as either condensers or evap-orators and the function of the refriyerant limiters 106 as expansion or by-pass devices.
In the preferred form of the invention the motor 110 and the compressor 109 are sealed within a sealed case 113 (Figure 2). The only lines piercing the shell of the sealed unit are the two connec-tions 114 and 115 to the evaporator and the condenser and the electrical connections 116A to the con-troller 112. In this manner the motor and purnp can both be provided in an ideal working enviromnent which is beneficial for lubrication of the bearings in the motor and the pump and which keeps any dirt or foreign matter from becoming entrained in the motor or pump which is particularly advantageous in an automotive operating environment to ensure long life of the working components. Furthermore by mounting the motor and pump within a sealed casing it is possible to eliminate individual bearing seals. This has the advantage of firstly reducing the friction on the motor/pump shaft which therefore allows the unit to operate at a higher efficiency and secondly permitting the compressor to operate at higher speed than would be possible with wiping seals, The sealed unit also oyercomes problems of fluid loss from the system.
The compressor may be provided in any suitable form, but is preferably provided in the form shown in Fi~ures 3 and 4A - 4H. In this configuration the pump or compressor takes the form of an outer rotor 117 and an inner rotor 116 mounted to rotate on a shaft 118 within a housing 119~ The inner rotor, the outer rotor and the housing are all of substantially the same thickness (apart from working clearancesl and are ,, . 1, , ~ ~
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'' ~0~ 6 mounted be-tween end plates 120 and 121. The end plate 120 incorporates an inle-t port communicating with an inlet openiny 122 and the end plate 121 incorpora-tes an outlet port which may communicate with an outlet openiny or in the case of the two staye compressor in Fiyure 3, may communicate with the inlet port of a further set of inner and outer rotors 123 and I24 mounted within a housing 125 against a final end plate 126.
The end plate 126 incorporates an outlet port 127 in communi-cation with an outlet aperture 128. The shaft 118 is mounted at one end in a beariny 129 housed in the end plate 120 and in a further bearing 130 mounted in a motor pump adaptor plate -~
131 and end plate 126 as will be described further below. The end plates, housings and motor pump adaptor plates are fastened toyether in asandwich-like manner, by mounting bolts 132 passing through holes 133 in each plate as shown. Each housing plate 119 has an off-set circular aperture therein, in which the outer rot~r 117 rotates. The inner rotor 116 has male lobes 134 which mate with female lobes 135 in the outer rotor.
The operation of the compressor will now be described with reference to Figures 4A - 4~1, which show in sequence the stages during one complete rotation of the inner rotor of the compressor. The outer rotor is provided with more female lobes 135 than the male lobes 134 of the inner rotor which may for example have seven and six lobes respectively as shown in Fiyure 3. In the form of compressor shown in Fic~s. 4A - 4H, the inner rotor is shown with 4 male lobes and the outer rotor with 5 female lobes for the sake of simplicity. In Fiyures 4A - 41-1 the inlet port is shown in broken outline at 136 and the outlet port, also in broken outline~ at 137. These ports are formed in the end plates 12Q and 121 resoectively. Durin~
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rotation of the compressor, because the outer rotor rotates in a circular housing which is offset with respect to the center of rotation of the shaft 118, one male lobe, for example 138, of the inner rotor meshes with the corresponding female lobe 139, whereas the opposite male lobe 140 passes across the arcuate portion 141, between 2 female lobes 142 and 143. As -the inner and outer rotors are rotated by the shaft 118 from the position shown in Fig. 4A to the position in Fig. 4B, the chamber 144 formed between the two rotors and shown shaded in the diagram is increased in volume, while being in communication with the inlet port 13~. This increase in volume continues through the position shown in Figure 4C and Figure 4D until, when the position shown in Figure 4D is reached, the chamber 144 is no longer in communication with the inlet port 136. As the rotation of the rotors continues to thepositionshown in Figure 4E the chamber 144 comes into communication with the outlet port 137, and the volume of the - chamber decreases through the positions shown in Figure 4F and Figure 4G. The ~orking fluid drawn into the ch~mber 144, through the inlet port, by the expansion of the chamber between the position shown in Figure 4~ and Figure 4D is then pressur-ized by further rotation of the rotors so that the working fluid is then forced out through the outlet port 137 between the positions shown in Figure 4E and Figure 4G, By virtue of the arcuate shapes between the male lobes of the inner rotor and between the female lobes of the outer rotor there is rolling line contact from lobe to lobe in the position shown in Fig.
4H. This contact effectively seals the inlet port from t~e outlet port and prevents any leakage, It will be seen from the relative ~otion of the dots 145 and 146 on the outer and . ~ , , - ~ ' inner rotors respectively, between the position shown in Fiyure 4A and the position in Figure 4H, that the outer rotor moves more slowly according to the ratio of the lobes on the rotors.
The rotors also act as slide valves over the ports 136 and 137 and may be improved in their sealing efficiency by a suitable coating such as a TEFLON (Registered Trade Mark) coating, over the end plate surface~
The compressor may be constructed as a single stage , compressor in the simple form, as shown in Figures 4A - 4H
or alternatively may be ganged as shown in Figure 3, where there are two such rotors, sandwiched either side of an end plate 121. This has the advantage that a compressor of any desired capacity (,~ii,thin the design range) may be assembled by simply adding further sets of components to give the required number of stages to achieve the desired compression ration. Manufacturing costs are thus kept to a minimum by reducing the number of different components required. In the form shown in Fig. 3, when viewed for clockwise rotation the transfer port 147 in the end plate serves as the outlet port for the rotors housed within the housing 119, and the in-let port for the rotors within the housing 125. To achieve -~
the desired working relationship, the circular aperture in the housing 119 is offset by 180 to the offset of the aperture .
in the housing 125. The outlet port 127 in the end plate 126 then corresponds with the outlet port 137 as shown in Figures 4A - 4H. The inlet and outlet apertures 122 and 128 are connected tothe conduits 114, 115 as shown in Figure 2.
It will be appreciated that although the compressor has been sho~n as a single stage in Figues 4A - 4H and a double stage in Figure 3, any number of stages may be provided to - g _ - : ~
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achieve the desired degree of compression simply by ganging or sandwiching together further rotor components of the form shown in Figure 3.
The compressor is provided with scavenge ports 148 protruding from the end plate 120 into the sealed area within the casing 113. One of the scavenge ports is connected through a non-return valve to the inlet port in the end plate 120 and the other scavenge valve is connected through an oppositely orientated non-return valve and through aligned apertures in the end plates and housing to the final port in the end plate 126. These scavenye valves serve to maintain the sealed pressure vessel 113 at reduced system pxessure, whether the heat pump is heating or cooling and prevents excessive buildup of lubricant within the pressure vessel. The scaVenge valves also maintain the motor and compressor at a lower temperature thus increasing efficiency.
It will be understood from a consideration of Figures : 4A - 4H that the compressor will serve to pump working fluid ~ ' in the opposite direction, if the direction of ~otation of the shaft 118 is reversed, and so the flow direction of the working fluid is dependent upon the direction o,f rotation of the motor 110. Because two scavena,e valves 14~ are provided with.oppo-sitely orient~ted non~return valves incorporated, there will always be a scaven~e valve open between the lnside of the pressuxe vessel and the inlet compressor port, It will bé apparent that by simply switching the direction of rotation of the motor 110, using the controller switching 112, the direction of flow of working fluid between the evaporator and the condenser may be reversed so that heat ma~ be pumped from the heat exchange unit 101 to the unit 103 . .. j . . .
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or visa versa as selected. .The remainder of the circuit, including the refrigerant limiters 106, is symm.etrical SQ that the only change necessary to reverse the heat flow direction is to change the direction of rotation of the compressor The compressor is driven by an electric motor and preferably by an induction motor comprising a motor frame 149 containing windin~s which connect to the power supply through the connections 116. The motor frame is mounted to the motor pump adapter plate 131~ A squirrel cage rotor 15Q is proyided, mounted directly onto the integrated compressor drive-shaft 118 which rotates in the bea.rings 129 and 130, The inner rotors 116 and 123 are keyed to the shaft 118 by way of shaft keys 151. .
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In this manner a heat pump is proyided which. is particularly suitable for automotive air conditioning and heating in that po~er may be drawn from the direct current power sup~ly of the vehicle and used to control in a simple yet effective ~ashion, the hea-t trans~er o.~ the heat pump ~ unit. Because the motor drive is independent from the dri~e from the engine of the automobile, it may be separ~tely ;~ mounted on:a part of the vehicle which is not prone to vibration and which will therefore minimize fatigue failure in the conduit line-108, The sealed motor compressor unit may also be mounted on the yehicle in any convenient locationl which will considerably simplify installation of air conditioning within the vehicle ~ecause the system is si~ple and fully reversible there is no need to provide a separate heating system within the vehicle, which therefore considerably reduces the cost of installation. The system is simple and because the motor and compressor may be constructed as described . .. ,.~
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, , , and mounted together within a sealed casing 113, service failure and maintenance should be kept to an absolute minimum.
The compressor characteristics can be desiyned specifically for the optimum working speed range of the motor, so that a high degree of efficiency and maximum utilization of the current drawn from -the battery B14 may be obtained.
Because the motor and compressor are designed to operate at a speed range in excess of 8,000 rpm, the size of - the sealed unit containing the motor and the compressor is able to be kept small and low in weight which leads to manufacturing economies. It is envisaged that the working speed range of the motor and compressor may extend to the region of 30,000 rpm. Because the unit operates at such high speed lt is pos-sible to achieve a high horse power output in a small size and also to achieve a high compression ratio from a lightweight and compact unit. Even in the least efficient example of the preferred form of the invention, i.e. with a single stage compressor operating at 8,000 rpm, it has been shown that an output pressure of 140 psi may be achieved from an input pres-sure of 40 psi. This is better than a 3:1 compression ratio and may be quickly e~tended as the speed of the motor is increased.
- The polyphase induction motor is also suitable to run at ideal turbine compressor operating speed and for some applications it may be desirable to substitute a turbine compressor for the positive displacement comp~essor described above. The turbiné compressor is likely to be particularly suitable for larger stationary applications.
Although the invention has been described in a pre-ferred form for application to a hea-t pump which may be used 18~
for the ~ir condi.tioning or heatiny of vehi.cles or any other air conditioning and he.at pump applications, it will be appreciated that the invention may also be applied to situations requiring an efficient and compact refrigeration system. The invention may be adapted to any refri~eration situation but is particularly suitable where portable refri~eration is required, for example fox use with refrigerated shipping or transportation containe:rA.
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Turning now to Figs. ~ tol~, the preferred embodi-ment of a control system 112 for the heat pump motor 110 will now be described. A block diagram of the control system of the preferred embodiment is illustrated in Fig. 1 and, in addition, the interconnection of the detailed circuit diagrams illustrated to Figs. 6 to 9 is also illustrated in Fig. 5.
- ~n oscillator 1 provides a pulse train to a logic supply ~ and also to a phase controller 6. The logic supply 2 converts the 12 volt DC voltage available at the vehicle batt-10 ery B14 to a 5 volt DC supply re~uired for some of the various integrated circuits forming the control system 112. A master clock 3 supplies a pulse train of variable pulse repetition rate to a phase sequencer 5, both the master clock 3 and phase sequencer 5 being controlled by switch controls 4. ~ terminal ; TS of the master clock 3 permits a feedback signal derived in any kno~n fashion to control the pulse xepetition rate of the master cloc~ 3. The output of the phase sequencer 5 is passed l: :
to a phase controller 6 which provides correctly timed switch-ing signals to a main switch 7 which connects each phase of the 20 nine phase delta, or preferably mesh, connected induction motor 110 to the correct terminals of the vehicle battery B14 in the correct sequence as will be explained here1nafter in detail.
In Fig. 6 the circuit details of the oscillator 1 and logic power supply 2 are shown. The oscillator 1 comprises IC13 (National 555) and resistors R114 and R115 together with capacitor C119. IC13 oscilates with a pulse repetition rate in the range of 60K Hz to 160K Hz, this rate being governed by the resistance value of resistors R114 and R115 in series which charge ca~acitor C119 until a threshold voltage is reached on the capacitor Cll9 which then discharges through ' ,8q~
resistor R11~, this cycle being repeated.
The remainder of the circuit illustrated in Fig. 6 comprises the logic supply 2 and it will be seen that the out-put from IC13 is passed to a divide-by-2 flip flop IC14A which divides the oscillator pulse repetition rate by 2 and, in addition, has complementary outputs with a precise 50% duty cycle.
The output of IC14A is passed to a DC to DC converter which comprises a push-pull arrangement operating through a transformer Tlll in which both the primary and secondary wind-ings are centre tapped. The outputs of IC14A are each passed through a series connected resistor and capacitor (R116 and CllO together with R117 and Clll) to respective buffer tran-sistor switches ~111 and Q112. The series connected resistor and capacitor prevent overload o.f the buffer transistors Qlll and Q112 in the event of failure of either IC13 or IC14A and also in the event of low input voltage to IC14A. Resistors R118 and Rll9 in the collector circuits of transistors Qlll and Q112 respectively reduce the load on the outputs of IC14A
and also limit the current through transistors Qlll and Q112.
It will be seén that transistors Qlll and Q112 toge~her with their respectively connected switching transist-ors Q113 and Q114 permit current to flow through their res-~
pective halves of the primary winding of transformer Tlll in alternate directions at a rate yoverned by the output of IC13 via IC14A~ Inductors Llll and L112 in.the collector circuits of transistors Q113 and Q114 respectivel~ present a high impedance to any parasitic oscillations whilst capacitors C112 and C113 introduce positive feedback to the bases of transist-ors Q113 and Q114 so as to reduce their switching times by removal of charge from their base-emitter junctions. Resistors R112 and R113 dampen this positive feedback to prevent self-oscillation. ~iodes Dll9 and D110 protect transistors Q113 and Q114 from any induced voltages of high magnitude and reverse polarity, and also permit current to decay after the transist-ors Q113 and Q114 have been switched off.
Transformer Tlll has a ferrite core and is a step-down transformer having only half the number of secondary wind-ings relative to the number of primary windings. Accordingly, a time varying vol-tage of approximately 6 volts a~pears across the secondary winding and this voltage is rectified by diodes Dlll and D112 and smoothed by capacitor C114 to provide a 5V
supply for some of the integrated circuits used throughout the control system. The lnterconnection of the logic power supply
In conven-tional automotive air conditioning systems, ' the compressor is driven directly from the motor vehicle engine and thereforè the speed of the compressor is dependent directly upon the speed of the motor vehicle engine. Accordingly regulation of tempera-ture must be brought about by means other than the speed of the compressor. However, in the present invention, temperature regulation is brought about directly by regulatiny the speed of the motor driving the compresso~. In' the preferred embodiment relating to automotive air condition-ing, a relatively low cos-t induction motor is used to drive the compressor and a control system is provided which permits the induction motor to be powered from the vehicle battery via a control system which permits the speed of the induction motor to be controlled and, hence, the temperature of the lnterior of the motor vehicle.
According to one aspect of the present invention there is disclosed a heat pump comprising an evaporator, a ' condenser, a pressure control device connected between the outlet from said condenser and the inlet to said evaporator, a compressor connected b'etween the outlet of said e~aporator and the inlet to said condenser, an electr'ic motor arranged to drive said compressor and a control system for said motor arranyed to enable the speed o;E said motor to be controlled as desired to adjust the amount of heat transferred from said evaporator to said condenser in use.
, ~ ccordiny to another aspect of the present inVention there is disclosed a control system for a polyphase motor havinq one winding per phase and being eneryised from a DC
supply, said control system comprising a pair of electrically operable switches for each phase of said motorr one switch of each pair being operative to connect the correspondin~ windiny of said motor to one terminal oE said DC supply and the other switch of each pair being operative to connect said correspond-ing winding to the other terminal of said DC supply; se~uenciny means connected to said switches to operate the switches of each pair alternatively and to simultaneously ope;rate one switch of every pair in sequence; and rate means connected to said sequencing means to control the rate o~ operation of said .
sequencing means whereby the rate of oneratio,n of said se~uencin-means controls the speed of operation of said polyphase motor, One embodiment of the ~resent invention will now be described with reference to the drawings in ~hich Fig, 1 is a diagrammatic perspective view of a heat pump system according to the invention;
Fig. 2 is a cross-sectional diagrammatic view of the sealed unit used in the heat pump shown in Fig. l;
Fig. 3 is an e~ploded perspective vie~ of the com-ponents of the motor and pump lncorporated within the sealed unit shown in Figure 2;
Figs. ~A - ~H are sequential cross-sectional views of the imneller section of the pump shown in Fig~ 3 at different stages in the pumping cycle.
Fiy. 5 is a block diayram of the preferred embodiment of the control system;
30 , Fiy. 6 is a circuit diagram of the oscillator and 5 - 3 ~
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volt logic power supply;
Fig. 7 is a circuit diagram of the master clock, switch controls and phase sequencer, Fig. 8 is a circuit diagram of the phase controller;
Fig. 9 is a circuit diagram of the main switch, and Fig. 10 is a yraph of the phase voltages applied to the induction motor as a function of time, In the preferred form of the invention a heat pump is constructed as an au-tomotive air-conditioning system although it will be appreciated that the invention may be equally well applied to a large number of heat pump applications.
Referring to Figure 1 the heat pump comprises a con-denser 101 which would normally be mounted towards the front of ; the vehicle, and whlch may be assisted by a fan 102 to draw cooling air through the condenser. An evaporator 103 is pro-vided, mounted within the vehicle and fans or blowers 104 may also be provided to force air through the evaporator 103 for the cooling of the interior of the vehicle. The evaporator and condenser are connected by a conduit 105 in which is incorpor-ated two unidirectional refrigerant limiters 106 and a receiver-drier 107. The refrigerant limiters act as expension valves, each in con~unction with a non-return valve orientated in opposite directions so that only one refrigerant li~iter is in operation at any one time. In the preferred form of the invent-ion the refrigerant limiters are in fact simple non-return valves arranged to have a predetermined amount of"leakage" in the normally closed direction. They therefore achieve substant-; ially unrestricted flo~7 in one direction and restricted flo~
against a predeterm1ned resistance in the opposite direction - 30 The air-conditioning unit is reversible as will be described :, -~ - 4 -.
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hereinafter so that in use as a heat pump the oppositely orientated refrigerant limiter comes into use to control the pressure distribution in the system.
The evaporator 101 and condenser 103 are further linked by a conduit 108 in which is mounted a compressor 109 driven by a motor 110. The motor is preferably provided in ` the form o~ an electric induction motor and the motor and com-pressor are preferably sealed together as a sealed unit within a casing 113. Electric power is supplied to the motor from an automotive battery B14 by way of a controller 112 which will be described in detail below.
When the system is used for cooling the interior of the automobile, heat is pumped using a suitable working fluid in the sy.stem, from the evaporator 103 to the condenser 101 where it is discharged to the atmosphere by the motion of ambient air through the condenser assisted, if necessary, by th~ fan 102. When it is desired to heat the interior of the automobile, the motor 110 is reversed by suitable switching in the control system 112, so that heat is then pumped from the condenser 101 which now acts as an evaporator to the evaporator 103, now acting as a condenser. In this reverse cycle, the oppositely orientated refrigerant limiter 106 comes into operation to giye pressure control in the desired direction.
The use of two refrigerant lim;ters, with non-return valves, acting as a by-pass, allows the refrigerant ~orking fluid to be bi directionally controlled by the operation of the sealed unit - comprising the compressor 109 and the motor 110. A dixect curxent is supplied by the bat~ery B14 to the control unit 112 which conyerts the current to alternating current for use by 3Q the sealed unit induction motor 110, The motor 110 drives the :, , ~ . , ., ' ' .
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compressor 109 in a direction which determines the function of the heat exchangers 101 and 103 as either condensers or evap-orators and the function of the refriyerant limiters 106 as expansion or by-pass devices.
In the preferred form of the invention the motor 110 and the compressor 109 are sealed within a sealed case 113 (Figure 2). The only lines piercing the shell of the sealed unit are the two connec-tions 114 and 115 to the evaporator and the condenser and the electrical connections 116A to the con-troller 112. In this manner the motor and purnp can both be provided in an ideal working enviromnent which is beneficial for lubrication of the bearings in the motor and the pump and which keeps any dirt or foreign matter from becoming entrained in the motor or pump which is particularly advantageous in an automotive operating environment to ensure long life of the working components. Furthermore by mounting the motor and pump within a sealed casing it is possible to eliminate individual bearing seals. This has the advantage of firstly reducing the friction on the motor/pump shaft which therefore allows the unit to operate at a higher efficiency and secondly permitting the compressor to operate at higher speed than would be possible with wiping seals, The sealed unit also oyercomes problems of fluid loss from the system.
The compressor may be provided in any suitable form, but is preferably provided in the form shown in Fi~ures 3 and 4A - 4H. In this configuration the pump or compressor takes the form of an outer rotor 117 and an inner rotor 116 mounted to rotate on a shaft 118 within a housing 119~ The inner rotor, the outer rotor and the housing are all of substantially the same thickness (apart from working clearancesl and are ,, . 1, , ~ ~
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'' ~0~ 6 mounted be-tween end plates 120 and 121. The end plate 120 incorporates an inle-t port communicating with an inlet openiny 122 and the end plate 121 incorpora-tes an outlet port which may communicate with an outlet openiny or in the case of the two staye compressor in Fiyure 3, may communicate with the inlet port of a further set of inner and outer rotors 123 and I24 mounted within a housing 125 against a final end plate 126.
The end plate 126 incorporates an outlet port 127 in communi-cation with an outlet aperture 128. The shaft 118 is mounted at one end in a beariny 129 housed in the end plate 120 and in a further bearing 130 mounted in a motor pump adaptor plate -~
131 and end plate 126 as will be described further below. The end plates, housings and motor pump adaptor plates are fastened toyether in asandwich-like manner, by mounting bolts 132 passing through holes 133 in each plate as shown. Each housing plate 119 has an off-set circular aperture therein, in which the outer rot~r 117 rotates. The inner rotor 116 has male lobes 134 which mate with female lobes 135 in the outer rotor.
The operation of the compressor will now be described with reference to Figures 4A - 4~1, which show in sequence the stages during one complete rotation of the inner rotor of the compressor. The outer rotor is provided with more female lobes 135 than the male lobes 134 of the inner rotor which may for example have seven and six lobes respectively as shown in Fiyure 3. In the form of compressor shown in Fic~s. 4A - 4H, the inner rotor is shown with 4 male lobes and the outer rotor with 5 female lobes for the sake of simplicity. In Fiyures 4A - 41-1 the inlet port is shown in broken outline at 136 and the outlet port, also in broken outline~ at 137. These ports are formed in the end plates 12Q and 121 resoectively. Durin~
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rotation of the compressor, because the outer rotor rotates in a circular housing which is offset with respect to the center of rotation of the shaft 118, one male lobe, for example 138, of the inner rotor meshes with the corresponding female lobe 139, whereas the opposite male lobe 140 passes across the arcuate portion 141, between 2 female lobes 142 and 143. As -the inner and outer rotors are rotated by the shaft 118 from the position shown in Fig. 4A to the position in Fig. 4B, the chamber 144 formed between the two rotors and shown shaded in the diagram is increased in volume, while being in communication with the inlet port 13~. This increase in volume continues through the position shown in Figure 4C and Figure 4D until, when the position shown in Figure 4D is reached, the chamber 144 is no longer in communication with the inlet port 136. As the rotation of the rotors continues to thepositionshown in Figure 4E the chamber 144 comes into communication with the outlet port 137, and the volume of the - chamber decreases through the positions shown in Figure 4F and Figure 4G. The ~orking fluid drawn into the ch~mber 144, through the inlet port, by the expansion of the chamber between the position shown in Figure 4~ and Figure 4D is then pressur-ized by further rotation of the rotors so that the working fluid is then forced out through the outlet port 137 between the positions shown in Figure 4E and Figure 4G, By virtue of the arcuate shapes between the male lobes of the inner rotor and between the female lobes of the outer rotor there is rolling line contact from lobe to lobe in the position shown in Fig.
4H. This contact effectively seals the inlet port from t~e outlet port and prevents any leakage, It will be seen from the relative ~otion of the dots 145 and 146 on the outer and . ~ , , - ~ ' inner rotors respectively, between the position shown in Fiyure 4A and the position in Figure 4H, that the outer rotor moves more slowly according to the ratio of the lobes on the rotors.
The rotors also act as slide valves over the ports 136 and 137 and may be improved in their sealing efficiency by a suitable coating such as a TEFLON (Registered Trade Mark) coating, over the end plate surface~
The compressor may be constructed as a single stage , compressor in the simple form, as shown in Figures 4A - 4H
or alternatively may be ganged as shown in Figure 3, where there are two such rotors, sandwiched either side of an end plate 121. This has the advantage that a compressor of any desired capacity (,~ii,thin the design range) may be assembled by simply adding further sets of components to give the required number of stages to achieve the desired compression ration. Manufacturing costs are thus kept to a minimum by reducing the number of different components required. In the form shown in Fig. 3, when viewed for clockwise rotation the transfer port 147 in the end plate serves as the outlet port for the rotors housed within the housing 119, and the in-let port for the rotors within the housing 125. To achieve -~
the desired working relationship, the circular aperture in the housing 119 is offset by 180 to the offset of the aperture .
in the housing 125. The outlet port 127 in the end plate 126 then corresponds with the outlet port 137 as shown in Figures 4A - 4H. The inlet and outlet apertures 122 and 128 are connected tothe conduits 114, 115 as shown in Figure 2.
It will be appreciated that although the compressor has been sho~n as a single stage in Figues 4A - 4H and a double stage in Figure 3, any number of stages may be provided to - g _ - : ~
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achieve the desired degree of compression simply by ganging or sandwiching together further rotor components of the form shown in Figure 3.
The compressor is provided with scavenge ports 148 protruding from the end plate 120 into the sealed area within the casing 113. One of the scavenge ports is connected through a non-return valve to the inlet port in the end plate 120 and the other scavenge valve is connected through an oppositely orientated non-return valve and through aligned apertures in the end plates and housing to the final port in the end plate 126. These scavenye valves serve to maintain the sealed pressure vessel 113 at reduced system pxessure, whether the heat pump is heating or cooling and prevents excessive buildup of lubricant within the pressure vessel. The scaVenge valves also maintain the motor and compressor at a lower temperature thus increasing efficiency.
It will be understood from a consideration of Figures : 4A - 4H that the compressor will serve to pump working fluid ~ ' in the opposite direction, if the direction of ~otation of the shaft 118 is reversed, and so the flow direction of the working fluid is dependent upon the direction o,f rotation of the motor 110. Because two scavena,e valves 14~ are provided with.oppo-sitely orient~ted non~return valves incorporated, there will always be a scaven~e valve open between the lnside of the pressuxe vessel and the inlet compressor port, It will bé apparent that by simply switching the direction of rotation of the motor 110, using the controller switching 112, the direction of flow of working fluid between the evaporator and the condenser may be reversed so that heat ma~ be pumped from the heat exchange unit 101 to the unit 103 . .. j . . .
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or visa versa as selected. .The remainder of the circuit, including the refrigerant limiters 106, is symm.etrical SQ that the only change necessary to reverse the heat flow direction is to change the direction of rotation of the compressor The compressor is driven by an electric motor and preferably by an induction motor comprising a motor frame 149 containing windin~s which connect to the power supply through the connections 116. The motor frame is mounted to the motor pump adapter plate 131~ A squirrel cage rotor 15Q is proyided, mounted directly onto the integrated compressor drive-shaft 118 which rotates in the bea.rings 129 and 130, The inner rotors 116 and 123 are keyed to the shaft 118 by way of shaft keys 151. .
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In this manner a heat pump is proyided which. is particularly suitable for automotive air conditioning and heating in that po~er may be drawn from the direct current power sup~ly of the vehicle and used to control in a simple yet effective ~ashion, the hea-t trans~er o.~ the heat pump ~ unit. Because the motor drive is independent from the dri~e from the engine of the automobile, it may be separ~tely ;~ mounted on:a part of the vehicle which is not prone to vibration and which will therefore minimize fatigue failure in the conduit line-108, The sealed motor compressor unit may also be mounted on the yehicle in any convenient locationl which will considerably simplify installation of air conditioning within the vehicle ~ecause the system is si~ple and fully reversible there is no need to provide a separate heating system within the vehicle, which therefore considerably reduces the cost of installation. The system is simple and because the motor and compressor may be constructed as described . .. ,.~
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, , , and mounted together within a sealed casing 113, service failure and maintenance should be kept to an absolute minimum.
The compressor characteristics can be desiyned specifically for the optimum working speed range of the motor, so that a high degree of efficiency and maximum utilization of the current drawn from -the battery B14 may be obtained.
Because the motor and compressor are designed to operate at a speed range in excess of 8,000 rpm, the size of - the sealed unit containing the motor and the compressor is able to be kept small and low in weight which leads to manufacturing economies. It is envisaged that the working speed range of the motor and compressor may extend to the region of 30,000 rpm. Because the unit operates at such high speed lt is pos-sible to achieve a high horse power output in a small size and also to achieve a high compression ratio from a lightweight and compact unit. Even in the least efficient example of the preferred form of the invention, i.e. with a single stage compressor operating at 8,000 rpm, it has been shown that an output pressure of 140 psi may be achieved from an input pres-sure of 40 psi. This is better than a 3:1 compression ratio and may be quickly e~tended as the speed of the motor is increased.
- The polyphase induction motor is also suitable to run at ideal turbine compressor operating speed and for some applications it may be desirable to substitute a turbine compressor for the positive displacement comp~essor described above. The turbiné compressor is likely to be particularly suitable for larger stationary applications.
Although the invention has been described in a pre-ferred form for application to a hea-t pump which may be used 18~
for the ~ir condi.tioning or heatiny of vehi.cles or any other air conditioning and he.at pump applications, it will be appreciated that the invention may also be applied to situations requiring an efficient and compact refrigeration system. The invention may be adapted to any refri~eration situation but is particularly suitable where portable refri~eration is required, for example fox use with refrigerated shipping or transportation containe:rA.
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Turning now to Figs. ~ tol~, the preferred embodi-ment of a control system 112 for the heat pump motor 110 will now be described. A block diagram of the control system of the preferred embodiment is illustrated in Fig. 1 and, in addition, the interconnection of the detailed circuit diagrams illustrated to Figs. 6 to 9 is also illustrated in Fig. 5.
- ~n oscillator 1 provides a pulse train to a logic supply ~ and also to a phase controller 6. The logic supply 2 converts the 12 volt DC voltage available at the vehicle batt-10 ery B14 to a 5 volt DC supply re~uired for some of the various integrated circuits forming the control system 112. A master clock 3 supplies a pulse train of variable pulse repetition rate to a phase sequencer 5, both the master clock 3 and phase sequencer 5 being controlled by switch controls 4. ~ terminal ; TS of the master clock 3 permits a feedback signal derived in any kno~n fashion to control the pulse xepetition rate of the master cloc~ 3. The output of the phase sequencer 5 is passed l: :
to a phase controller 6 which provides correctly timed switch-ing signals to a main switch 7 which connects each phase of the 20 nine phase delta, or preferably mesh, connected induction motor 110 to the correct terminals of the vehicle battery B14 in the correct sequence as will be explained here1nafter in detail.
In Fig. 6 the circuit details of the oscillator 1 and logic power supply 2 are shown. The oscillator 1 comprises IC13 (National 555) and resistors R114 and R115 together with capacitor C119. IC13 oscilates with a pulse repetition rate in the range of 60K Hz to 160K Hz, this rate being governed by the resistance value of resistors R114 and R115 in series which charge ca~acitor C119 until a threshold voltage is reached on the capacitor Cll9 which then discharges through ' ,8q~
resistor R11~, this cycle being repeated.
The remainder of the circuit illustrated in Fig. 6 comprises the logic supply 2 and it will be seen that the out-put from IC13 is passed to a divide-by-2 flip flop IC14A which divides the oscillator pulse repetition rate by 2 and, in addition, has complementary outputs with a precise 50% duty cycle.
The output of IC14A is passed to a DC to DC converter which comprises a push-pull arrangement operating through a transformer Tlll in which both the primary and secondary wind-ings are centre tapped. The outputs of IC14A are each passed through a series connected resistor and capacitor (R116 and CllO together with R117 and Clll) to respective buffer tran-sistor switches ~111 and Q112. The series connected resistor and capacitor prevent overload o.f the buffer transistors Qlll and Q112 in the event of failure of either IC13 or IC14A and also in the event of low input voltage to IC14A. Resistors R118 and Rll9 in the collector circuits of transistors Qlll and Q112 respectively reduce the load on the outputs of IC14A
and also limit the current through transistors Qlll and Q112.
It will be seén that transistors Qlll and Q112 toge~her with their respectively connected switching transist-ors Q113 and Q114 permit current to flow through their res-~
pective halves of the primary winding of transformer Tlll in alternate directions at a rate yoverned by the output of IC13 via IC14A~ Inductors Llll and L112 in.the collector circuits of transistors Q113 and Q114 respectivel~ present a high impedance to any parasitic oscillations whilst capacitors C112 and C113 introduce positive feedback to the bases of transist-ors Q113 and Q114 so as to reduce their switching times by removal of charge from their base-emitter junctions. Resistors R112 and R113 dampen this positive feedback to prevent self-oscillation. ~iodes Dll9 and D110 protect transistors Q113 and Q114 from any induced voltages of high magnitude and reverse polarity, and also permit current to decay after the transist-ors Q113 and Q114 have been switched off.
Transformer Tlll has a ferrite core and is a step-down transformer having only half the number of secondary wind-ings relative to the number of primary windings. Accordingly, a time varying vol-tage of approximately 6 volts a~pears across the secondary winding and this voltage is rectified by diodes Dlll and D112 and smoothed by capacitor C114 to provide a 5V
supply for some of the integrated circuits used throughout the control system. The lnterconnection of the logic power supply
2 to the re~aining integrated circuits is not illustrated in detail and will be clear to those s~illed in the art. -~
As seen in Fig. 7, the switch control~ 4 include a manually operated 3 position switch having ganged contacts Sl and S2, the centre position represents an OFF position whilst the two operative positions represent COLD (forward) and HOT
(reverse).
It will be seen that operation of the s~itch controls 4 causes one of capacitors C121 or C122 to be charged via resistors R121 or R122 respectively to the 12V supply from the vehicle hattery B14 whilst simultaneously the other one of capacitors C121 and C122 is discharged via diode D121 or D122 respectively to ground. In conse~uence, the in-put of only one ~ `,':' ' ` .
:
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of two Schmitt trigyers IC9A and IC9B goes positive thereb~
causing the output of AND ya-te IC8 B,C to go negative. This change of logic state is passed via inverter ICllD to divide-by 2 flip flop IC14B of Fig. 8 to enable same. In addition, the change of logic s-tate is passed via resistor R123 and diode D123 to the positive input of integrator IClA.
The integrator IClA is connected to provide a voltage ramp to series connected resistors R126 and R127 which is initially positive and reduces in magnitude within increasing time. The change of logic state produced by ~ND gate IC8B,C
ensures that a maximum positive voltage is initially present at the output of integrator IClA thereby ensuring that the master clock IC2 is slowed to a low starting speed in the vicinity of 200Hz. As the voltage on the positve input of the integrator IClA decays, due to the charging of capacitor C123, simultaneously the voltage at the negative input of integrator IClA rises due to current through resistor R125 and diode D125 discharging the capacitor C124. In consequence, th~
voltage at the output o integrator IClA falls, thereby causing . .
the voltage at the ~unction o~ resistors R126 and R127 to fall and producing an increase in the pulse repetition rate of the ~" .
master cloc~ IC2 to a preset maximum. This preset maximum will be be determined by the preset value of resistor R120 and also by a voltage applied to the terminal TS by a conventional temp-erature sensor (not illustrated).
The master cloc~ IC2 is an LM322 timer operating in an astable mode by feeding a fraction of its output bac~ to its trigger input via capacitor C126. The operating frequency of the master clock IC2 is 1/(R120+R129).(C125) Hz whilst the .. ' ~, ' - ' .
.- . ~ . :
-, output is a narrow negative pulse o width approximately 2(R128).(C126) seconds.
The output of the master clock IC2 is passed directly to line l~ of Fig. 8' and also to two cascaded counters IC3 and IC4 via a potential divider formed by resistors R1212 and R1213.
The outputs of counters IC3 and IC4 are connected to the address 'inputs of three memories IC6, IC7 and IC12. The counters IC3 and IC4 always count in the same direction and are reset by NAND gate IC8A~
10It will be seen that the output of Schmitt trigger - IC9B is connected to flip flop IC5 which determines whether . forward or reverse operation is to ta]~e place. This is achiev-ed by the output of fli flop IC5 comprising the most signifi-cant bit of the address input to memories IC6, IC7 and IC12, as illustrated in Table I~ The reseting of the counters IC3 and IC4 via NAND gate IC8A is the same for both forward and reverse functions, however, the output of flip flop IC5 switches the memories IC6, IC7 and IC12 to two distinct and dlfferent fields of addresses where the forward.and reverse programmes respectively are stored.
It will be seen from Table I that the outputs of the memories IC6, IC7 and IC12 comprise 9 bits and the complement of each of these bits is provided by nine inverters IClOA to IClOF and ICllA to ICllC respectively. The output,bits of-the memories IC6, IC7 and IC12, and their complements, are passed directly to the phase controller 6 illustrated in Fig.
8 .
In addition, the output of integrator IClA of Fig.
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As seen in Fig. 7, the switch control~ 4 include a manually operated 3 position switch having ganged contacts Sl and S2, the centre position represents an OFF position whilst the two operative positions represent COLD (forward) and HOT
(reverse).
It will be seen that operation of the s~itch controls 4 causes one of capacitors C121 or C122 to be charged via resistors R121 or R122 respectively to the 12V supply from the vehicle hattery B14 whilst simultaneously the other one of capacitors C121 and C122 is discharged via diode D121 or D122 respectively to ground. In conse~uence, the in-put of only one ~ `,':' ' ` .
:
~,, .
of two Schmitt trigyers IC9A and IC9B goes positive thereb~
causing the output of AND ya-te IC8 B,C to go negative. This change of logic state is passed via inverter ICllD to divide-by 2 flip flop IC14B of Fig. 8 to enable same. In addition, the change of logic s-tate is passed via resistor R123 and diode D123 to the positive input of integrator IClA.
The integrator IClA is connected to provide a voltage ramp to series connected resistors R126 and R127 which is initially positive and reduces in magnitude within increasing time. The change of logic state produced by ~ND gate IC8B,C
ensures that a maximum positive voltage is initially present at the output of integrator IClA thereby ensuring that the master clock IC2 is slowed to a low starting speed in the vicinity of 200Hz. As the voltage on the positve input of the integrator IClA decays, due to the charging of capacitor C123, simultaneously the voltage at the negative input of integrator IClA rises due to current through resistor R125 and diode D125 discharging the capacitor C124. In consequence, th~
voltage at the output o integrator IClA falls, thereby causing . .
the voltage at the ~unction o~ resistors R126 and R127 to fall and producing an increase in the pulse repetition rate of the ~" .
master cloc~ IC2 to a preset maximum. This preset maximum will be be determined by the preset value of resistor R120 and also by a voltage applied to the terminal TS by a conventional temp-erature sensor (not illustrated).
The master cloc~ IC2 is an LM322 timer operating in an astable mode by feeding a fraction of its output bac~ to its trigger input via capacitor C126. The operating frequency of the master clock IC2 is 1/(R120+R129).(C125) Hz whilst the .. ' ~, ' - ' .
.- . ~ . :
-, output is a narrow negative pulse o width approximately 2(R128).(C126) seconds.
The output of the master clock IC2 is passed directly to line l~ of Fig. 8' and also to two cascaded counters IC3 and IC4 via a potential divider formed by resistors R1212 and R1213.
The outputs of counters IC3 and IC4 are connected to the address 'inputs of three memories IC6, IC7 and IC12. The counters IC3 and IC4 always count in the same direction and are reset by NAND gate IC8A~
10It will be seen that the output of Schmitt trigger - IC9B is connected to flip flop IC5 which determines whether . forward or reverse operation is to ta]~e place. This is achiev-ed by the output of fli flop IC5 comprising the most signifi-cant bit of the address input to memories IC6, IC7 and IC12, as illustrated in Table I~ The reseting of the counters IC3 and IC4 via NAND gate IC8A is the same for both forward and reverse functions, however, the output of flip flop IC5 switches the memories IC6, IC7 and IC12 to two distinct and dlfferent fields of addresses where the forward.and reverse programmes respectively are stored.
It will be seen from Table I that the outputs of the memories IC6, IC7 and IC12 comprise 9 bits and the complement of each of these bits is provided by nine inverters IClOA to IClOF and ICllA to ICllC respectively. The output,bits of-the memories IC6, IC7 and IC12, and their complements, are passed directly to the phase controller 6 illustrated in Fig.
8 .
In addition, the output of integrator IClA of Fig.
- 18 - , :
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3~Eii -7 is passed via resistor R1~14 to Schmi-tt triyger IC9C, the output of which is connected to the base of transistor Q125.
The collector of transistor Q125 is connected to the 12V supply whilst the emitter transistor Q125 is connected to line Z of Fig. 8 . The volta~e ramp appearing at the output of integrat-or IClA initially enables Schmitt trigger IC9C thus turning transistor Q125 ON. Therefore initially line Z of Fig. 8 is effectively connected to the 12V supply, however after a pre-determined delay, transistor Q125 is turned OFF, thereby effectively disconnecting line Z of Fig.-8- from the 12V
su~ply.
In Fig. 8 , the circuit details of the phase con-- troller 6 are illustrated, however, only the details of a single phase of the 9 phases of the preferred embodiment are illustrated in order to avoid repetition.-Some aspec-ts of the circuit of Fig. 8 are similar to the circuit of Fig. 6 . ~ divide-by-2 flip flop IC14B is provided and, like the divide-by-2 flip flop IC14~ of Fig. 6~, IC14B is also connected to the output of IC13 of Fig. 6 which comprises the output of the oscillator 1 of Fig. 5 . In - addition, the output of invert0r ICllD of Fig. 7 is also connected to IC14B in order to provide an on/off control for the operation of the divide-by-2 -flip flop IC14B.
In a manner similar to that of Fig. 6~, the outputs of flip flop IC14B of Fig. 8 are passed via series connected capacitors and resistors C131 and R135, R136 respectively, to transistor switches Q135, Q136 and Q137, Q138 respectively.
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These transistor switches switch the lines X and Y of Fig. 8 to ground alternately at half the rate determined by the pulse repetition rate of the oscillator 1.
Each phase of the phase controller 6 comprises two identical circuits which'are required to produce complementary outputs for the two switches per phase terminal of the main switch 7 illustrated in detail in Fig. 9 . Each of the identical circuits of the phase controller 6 comprises one of bistables IC15 to IC32 respectively and one of transformers T131 to T149 respectively togetner with associated circuitry.
Each of the bistables IC15 to IC32 comprises a National 555 - which is switchable between a monostable state and a set-reset flip flop state.
The trigger input of each bistable IC15 to IC32 is connected to line W and therefore receives the output of master cloc~ IC2. In addition, the output and input of the inverter for eacn phase of the phase sequencer 5 are connected to the inhibit/enable input of the corresyonding bistable for ~that phase. Thus the outpu-t (IClOA) of inverter IClOA is connected to the inhibit/enable input of bistable IC15 and ~ ~ the input (IClOA) of inverter IClOA is connected to ~he inhibit/
;~ enable input of bistable IC16.
.
Each of the bistables IC15 to IC32 is respectively connected to the line Z by means of a respective resistor.
For example bistables IC15 and ICl~ are connected to the line Z by means of resistors R1324 and R1235 respectively. ~he out-put of each bistable IC15 to IC32 is connected to the centre tap of the primary w-ndlng of the corresponding transformer and ., -, . ' -, .. :
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3~
therefore the output of bistable IC15 is connected to the centre tap of the primary winding of transformer T131.
In order to avoid the voltage drop of the diodes D111 ; and D112 of Fig. 6, transistors Q131 and Q132 are connected to the secondary winding of transformer 131 with resistors R131 and R132 respectively providing base current in order to saturate the transistors Q131 and Q132 when they are required to conduct. In this way the low collector-emitter saturation voltage of the transistors replaces the relatively larye forward voltage drop of the diodes, thereby avoiding a sub-stantial power loss.
After operation of the switch controls 4 as described in detail with reference to Fig. 7, line Z is initially conn-ected to the 12V supply and therefore each of bistables IC15 to IC32 operates as a monostable producing a pulse of predeterm-ined duration for each pulse applied to the trigger input via line W.
Thus when bistable IC15 is enabled by the output IC101~, for each pulse produced by master clock IC2 a corres-ponding pulse of predetermined length appears at the output of bistable IC15 and is applied to the centre tap of the primary wlnding of transformer T131. However, wnen bistable IC15 is inhibited by the output IClOP. no pulses are applied to the transformer T131. ~ecause of the complementary relatlonship be-tween outputs IClOA and IClOA, either bistable IC15 is enabl-ed and bistable IC16 is inhibited or visa versa.
During the initial starting time the pulses produced by master clock IC2- increase in repetitio~ rate and thus tne output of .
' 33~ii ,, .
each of the bistables IC15 to IC32 comprises a pulse train in which there are a plurality of pulses for half the period and no pulses for the remainder of the period, the mark space ratio of the plurality of pulses increasing as the frequency of the master clock IC2 increases.
In this way the pulse w~ eform illustrated in Fig.-10 (to be described hereinafter) is altered so that the effective voltage of each half period pulse is reduced by modulation.
The modulation is such that the effective applied voltage is reduced from its maximum possible value by the provision of an adjustable number of short pulses each of the same duration during the time allocated for the half period pulse present during normal operation.
The abovedescribed modulation permits the motor 110 to be s-tarted smoothly and run up to maximum speed. Thus initially an effective phase voltage of only 0.3V is applied compared with an effective full speed phase voltage of 12V.
Furthermore, the initial start up period is able to be adjusted, as is the maximum speed, so that the control system is able to drive a wide range of loads under different condit-ions. The use of feedbac~ terminals TS permits this adjustment to be automatically achieved by means of conventional feedback techniques.
This initial method of operation continues until the line Z is disconnected from the 12V supply after a predeter-mined time thereby causing each of bistables IC15 to IC32 to operate in a set-reset flip flop mode. In this mode, the first pulse received by bistable IC15, for example, causes a single pulse to be applied to the centre tap of the primary winding of the transformer T131, the duration of this pulse being , . .
. : ' " - " ~:
3~
determined when output IC10~ resets bistable IC15. Thus the output of each bistable IC15 to IC32 comprises a square wave o~
50~ mark space ratio.
This timing sequence is used to permit the motor 110 to be started at a low speed and then, after the abovementioned predetermined period, be operated at a faster speed.
It will be apparent to those skilled in the art that the circuitry associated with each of the transformers T131 to Tl~9 is very similar to that described in Fig. 6 save that there 10 is not filtering of the output of the secondary winding. Thus for transformer T131, the output voltage a~appearing between the centre tap of the secondary winding of transformer T131 and the emitters of transistors Q131 and Q132 is an amplified or attenuated reproduction of the output voltage of the bi-stable IC15. The degree of such amplification or attenuation is dependent upon the turns ratio of each of transformers T131 t~ Tl~9. In additi~n, the .
.
:,, .
'' ~, ,'", "'' ' `. , .
- 10~1836 outpu-t voltage a of transformer T132 is the complement G~ vol-tage a.
The main switch 7, to which the phase controller 6 of Fig. 8 is connected, is illustrated in detail in Fig. 9 The main switch ~or 9 phases A, B, C, D, E, F, G, H and I" each spaced 40 apart in time, comprises two transistor switches for each phase. ~or phase A one transistor switch comprises transistor Q141 together with resistor R141 and diode D141 whilst the other switch comprises transistor Q142, resistor R142 and diode D142. The phase terminal A of Fig. ~ is connected to the winding of phase A of the 9 phase delta, or preferably mesh, connected induction motor 110, however, if desired another type of polyphase motor such as a synchronous-motor could be used instead. -~
The voltage a is applied to resistor R141 of Fig.-9 , that is the emitter of transistor Q141 iS connected to the centre tapping of the secondary winding of transformer T13I
whilst the base of transistor Q141 is connected to the emitters ~-~ of transistors Q131 and 132 of Fig. 8. Similarly voltage a (the complement of voltage a) is connected across resistor 1~142.
When voltage a is positive transistor Q141 is turned ON thereby connecting phase terminal A to -the positive terminal o~ the vehicle battery ~14. At the same time as voltage a ceases to be positive, voltage a becomes positive and therefore transistor Q141 turns OFF whilst transistor Q142 turns ON there-by connecting phase terminal A to the negative terminal of battery B14. In this way a pulsed voltage waveform as illus-,, .
, '' .
- ~4 . . , ~
- :; -:.
: . -:
: ::
trated in Fig. 10 is generated for each phase. ~ecause of the inductance of each winding to which the pulsed waveform is applied and the interphase coupling, the current for each phase is substantially sinusoidal. The diodes D141 and D142 are provided to ~ermi-t currel1t to flow when transistors Q141 and Q142 have been turned OFF respectively.
It will be apparent tha-t the rate at which transistors Q141 and Q142 are switched is the rate determined by the master clock IC2 of Fig. 7 and therefore this rate determines the speed at which the induction motor 110 operates.
Furthermore, the pair of switches for each phase are operated so that each switch of a pair is turned on and off alternately, however, corresponding switches of each pair are operated ln sequence so that there is identical time displace-ment between each phase resulting in the voltage waveform for each phase as illustrated in Fig. 10, except durin~ the initial start up.
The preferred make and type for each of the integrat-ed circuits referred to above is as follows:-ICl(A)National 3900 IC2 " LM322 IC3 " 74LS163 . .
IC4 " 74LS163 ; IC5 " 4027 IC6 Harris HM7611 - IC7 Harris HM7611 IC8(A-C) National 7400 IC9(A-C) National 74C14 IC10(A-F) National 7404 .- ' .' - : ~ ' ' 8~i ICll~A-D) National 7404 IC12 Harris HM7611 IC13 National 555 IC14(A-B) National 4027 IC15-IC32 National 555 It wlll also be apparent to those s]cilled in the art that the two cascaded counters IC3 and IC4 and the memories IC6, IC7 and IC12 can be replaced by a shift register in which a word, comprising twice the number of bits as the memory out-put, is initially stored in the shift register when power is -applied to the circult and this word is shifted cyclically at a rate determined by the master cloc~. In this way an output : identical to that o~ memories IC6, IC7 and IC12 can be obtained. In this arrangement reversal of the motor 110 is achieved by reversing the shift direction of the shift register.
~he same res~lt _s lso able to be achieved with data selectors.
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The collector of transistor Q125 is connected to the 12V supply whilst the emitter transistor Q125 is connected to line Z of Fig. 8 . The volta~e ramp appearing at the output of integrat-or IClA initially enables Schmitt trigger IC9C thus turning transistor Q125 ON. Therefore initially line Z of Fig. 8 is effectively connected to the 12V supply, however after a pre-determined delay, transistor Q125 is turned OFF, thereby effectively disconnecting line Z of Fig.-8- from the 12V
su~ply.
In Fig. 8 , the circuit details of the phase con-- troller 6 are illustrated, however, only the details of a single phase of the 9 phases of the preferred embodiment are illustrated in order to avoid repetition.-Some aspec-ts of the circuit of Fig. 8 are similar to the circuit of Fig. 6 . ~ divide-by-2 flip flop IC14B is provided and, like the divide-by-2 flip flop IC14~ of Fig. 6~, IC14B is also connected to the output of IC13 of Fig. 6 which comprises the output of the oscillator 1 of Fig. 5 . In - addition, the output of invert0r ICllD of Fig. 7 is also connected to IC14B in order to provide an on/off control for the operation of the divide-by-2 -flip flop IC14B.
In a manner similar to that of Fig. 6~, the outputs of flip flop IC14B of Fig. 8 are passed via series connected capacitors and resistors C131 and R135, R136 respectively, to transistor switches Q135, Q136 and Q137, Q138 respectively.
, ~ . ....
8:3~
These transistor switches switch the lines X and Y of Fig. 8 to ground alternately at half the rate determined by the pulse repetition rate of the oscillator 1.
Each phase of the phase controller 6 comprises two identical circuits which'are required to produce complementary outputs for the two switches per phase terminal of the main switch 7 illustrated in detail in Fig. 9 . Each of the identical circuits of the phase controller 6 comprises one of bistables IC15 to IC32 respectively and one of transformers T131 to T149 respectively togetner with associated circuitry.
Each of the bistables IC15 to IC32 comprises a National 555 - which is switchable between a monostable state and a set-reset flip flop state.
The trigger input of each bistable IC15 to IC32 is connected to line W and therefore receives the output of master cloc~ IC2. In addition, the output and input of the inverter for eacn phase of the phase sequencer 5 are connected to the inhibit/enable input of the corresyonding bistable for ~that phase. Thus the outpu-t (IClOA) of inverter IClOA is connected to the inhibit/enable input of bistable IC15 and ~ ~ the input (IClOA) of inverter IClOA is connected to ~he inhibit/
;~ enable input of bistable IC16.
.
Each of the bistables IC15 to IC32 is respectively connected to the line Z by means of a respective resistor.
For example bistables IC15 and ICl~ are connected to the line Z by means of resistors R1324 and R1235 respectively. ~he out-put of each bistable IC15 to IC32 is connected to the centre tap of the primary w-ndlng of the corresponding transformer and ., -, . ' -, .. :
, -.
3~
therefore the output of bistable IC15 is connected to the centre tap of the primary winding of transformer T131.
In order to avoid the voltage drop of the diodes D111 ; and D112 of Fig. 6, transistors Q131 and Q132 are connected to the secondary winding of transformer 131 with resistors R131 and R132 respectively providing base current in order to saturate the transistors Q131 and Q132 when they are required to conduct. In this way the low collector-emitter saturation voltage of the transistors replaces the relatively larye forward voltage drop of the diodes, thereby avoiding a sub-stantial power loss.
After operation of the switch controls 4 as described in detail with reference to Fig. 7, line Z is initially conn-ected to the 12V supply and therefore each of bistables IC15 to IC32 operates as a monostable producing a pulse of predeterm-ined duration for each pulse applied to the trigger input via line W.
Thus when bistable IC15 is enabled by the output IC101~, for each pulse produced by master clock IC2 a corres-ponding pulse of predetermined length appears at the output of bistable IC15 and is applied to the centre tap of the primary wlnding of transformer T131. However, wnen bistable IC15 is inhibited by the output IClOP. no pulses are applied to the transformer T131. ~ecause of the complementary relatlonship be-tween outputs IClOA and IClOA, either bistable IC15 is enabl-ed and bistable IC16 is inhibited or visa versa.
During the initial starting time the pulses produced by master clock IC2- increase in repetitio~ rate and thus tne output of .
' 33~ii ,, .
each of the bistables IC15 to IC32 comprises a pulse train in which there are a plurality of pulses for half the period and no pulses for the remainder of the period, the mark space ratio of the plurality of pulses increasing as the frequency of the master clock IC2 increases.
In this way the pulse w~ eform illustrated in Fig.-10 (to be described hereinafter) is altered so that the effective voltage of each half period pulse is reduced by modulation.
The modulation is such that the effective applied voltage is reduced from its maximum possible value by the provision of an adjustable number of short pulses each of the same duration during the time allocated for the half period pulse present during normal operation.
The abovedescribed modulation permits the motor 110 to be s-tarted smoothly and run up to maximum speed. Thus initially an effective phase voltage of only 0.3V is applied compared with an effective full speed phase voltage of 12V.
Furthermore, the initial start up period is able to be adjusted, as is the maximum speed, so that the control system is able to drive a wide range of loads under different condit-ions. The use of feedbac~ terminals TS permits this adjustment to be automatically achieved by means of conventional feedback techniques.
This initial method of operation continues until the line Z is disconnected from the 12V supply after a predeter-mined time thereby causing each of bistables IC15 to IC32 to operate in a set-reset flip flop mode. In this mode, the first pulse received by bistable IC15, for example, causes a single pulse to be applied to the centre tap of the primary winding of the transformer T131, the duration of this pulse being , . .
. : ' " - " ~:
3~
determined when output IC10~ resets bistable IC15. Thus the output of each bistable IC15 to IC32 comprises a square wave o~
50~ mark space ratio.
This timing sequence is used to permit the motor 110 to be started at a low speed and then, after the abovementioned predetermined period, be operated at a faster speed.
It will be apparent to those skilled in the art that the circuitry associated with each of the transformers T131 to Tl~9 is very similar to that described in Fig. 6 save that there 10 is not filtering of the output of the secondary winding. Thus for transformer T131, the output voltage a~appearing between the centre tap of the secondary winding of transformer T131 and the emitters of transistors Q131 and Q132 is an amplified or attenuated reproduction of the output voltage of the bi-stable IC15. The degree of such amplification or attenuation is dependent upon the turns ratio of each of transformers T131 t~ Tl~9. In additi~n, the .
.
:,, .
'' ~, ,'", "'' ' `. , .
- 10~1836 outpu-t voltage a of transformer T132 is the complement G~ vol-tage a.
The main switch 7, to which the phase controller 6 of Fig. 8 is connected, is illustrated in detail in Fig. 9 The main switch ~or 9 phases A, B, C, D, E, F, G, H and I" each spaced 40 apart in time, comprises two transistor switches for each phase. ~or phase A one transistor switch comprises transistor Q141 together with resistor R141 and diode D141 whilst the other switch comprises transistor Q142, resistor R142 and diode D142. The phase terminal A of Fig. ~ is connected to the winding of phase A of the 9 phase delta, or preferably mesh, connected induction motor 110, however, if desired another type of polyphase motor such as a synchronous-motor could be used instead. -~
The voltage a is applied to resistor R141 of Fig.-9 , that is the emitter of transistor Q141 iS connected to the centre tapping of the secondary winding of transformer T13I
whilst the base of transistor Q141 is connected to the emitters ~-~ of transistors Q131 and 132 of Fig. 8. Similarly voltage a (the complement of voltage a) is connected across resistor 1~142.
When voltage a is positive transistor Q141 is turned ON thereby connecting phase terminal A to -the positive terminal o~ the vehicle battery ~14. At the same time as voltage a ceases to be positive, voltage a becomes positive and therefore transistor Q141 turns OFF whilst transistor Q142 turns ON there-by connecting phase terminal A to the negative terminal of battery B14. In this way a pulsed voltage waveform as illus-,, .
, '' .
- ~4 . . , ~
- :; -:.
: . -:
: ::
trated in Fig. 10 is generated for each phase. ~ecause of the inductance of each winding to which the pulsed waveform is applied and the interphase coupling, the current for each phase is substantially sinusoidal. The diodes D141 and D142 are provided to ~ermi-t currel1t to flow when transistors Q141 and Q142 have been turned OFF respectively.
It will be apparent tha-t the rate at which transistors Q141 and Q142 are switched is the rate determined by the master clock IC2 of Fig. 7 and therefore this rate determines the speed at which the induction motor 110 operates.
Furthermore, the pair of switches for each phase are operated so that each switch of a pair is turned on and off alternately, however, corresponding switches of each pair are operated ln sequence so that there is identical time displace-ment between each phase resulting in the voltage waveform for each phase as illustrated in Fig. 10, except durin~ the initial start up.
The preferred make and type for each of the integrat-ed circuits referred to above is as follows:-ICl(A)National 3900 IC2 " LM322 IC3 " 74LS163 . .
IC4 " 74LS163 ; IC5 " 4027 IC6 Harris HM7611 - IC7 Harris HM7611 IC8(A-C) National 7400 IC9(A-C) National 74C14 IC10(A-F) National 7404 .- ' .' - : ~ ' ' 8~i ICll~A-D) National 7404 IC12 Harris HM7611 IC13 National 555 IC14(A-B) National 4027 IC15-IC32 National 555 It wlll also be apparent to those s]cilled in the art that the two cascaded counters IC3 and IC4 and the memories IC6, IC7 and IC12 can be replaced by a shift register in which a word, comprising twice the number of bits as the memory out-put, is initially stored in the shift register when power is -applied to the circult and this word is shifted cyclically at a rate determined by the master cloc~. In this way an output : identical to that o~ memories IC6, IC7 and IC12 can be obtained. In this arrangement reversal of the motor 110 is achieved by reversing the shift direction of the shift register.
~he same res~lt _s lso able to be achieved with data selectors.
;, .
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Claims (15)
1. A heat pump comprising an evaporator, a condenser, a pressure control device connected between the outlet from said condenser and the inlet to said evaporator, a compressor connected between the outlet of said evaporator and the inlet to said condenser, an electric motor arranged to drive said compressor and a control system for said motor arranged to enable the speed of said motor to be controlled as desired to adjust the amount of heat transferred from said evaporator to -
2. A heat pump as claimed in claim 1 when arranged to be reversible so that said condenser acts as an evaporator and said evaporator acts as a condenser and wherein said motor is reversible in direction and said pressure control device is operable to control pressure drop in a working fluid passing in either direction between said evaporator and said condenser.
3. A heat pump as claimed in claim 2 wherein said pressure control device comprises a pair of oppositely orient-ated refrigerant limiters arranged in a connecting conduit between said evaporator and said condenser, each said refriger-ant limiter comprising a valve arranged to pass working fluid therethrough in a substantially unrestricted flow in one direction and in a restricted flow against a predetermined resistance in the opposite direction.
4. A heat pump as claimed in claim 1 wherein said motor comprises a polyphase induction motor energised from a DC supply through said control system.
5. A heat pump as claimed in claim 1 wherein said compressor comprises an inner rotor having a plurality of male lobes mounted on and driven by a drive shaft, an outer rotor of substantially the same thickness as said inner rotor having a plurality of female lobes greater in number than and meshed with the male lobes of said inner rotor, said outer rotor having a circular periphery rotatable in a circular aperture within a housing plate, said circular aperture having a center offset from the center of said shaft so that said inner rotor meshes with said outer rotor to form a plurality of working chambers of varying volume, a pair of end plates fastened to said housing plate so that said inner and outer rotors rotate therebetween, and inlet and outlet ports suitably located in said end plates so that said inlet port is in communication with each said working chamber as said working chamber increases in volume and said outlet port is in communication with said working chamber as said working chamber decreases in volume, said inlet and outlet ports being substantially symmetrical so that said compressor is reversible.
6. A heat pump as claimed in claim 5 wherein said compressor is provided with a plurality of stages, each addit-ional stage comprising an additional housing plate, outer rotor, inner rotor and end plate axially ganged onto the preceding end plate and having the offset in said housing radially dis-placed by 180° from the offset of the preceding stage so that the inlet port in the end plate of one stage also acts as the outlet port from the preceding stage.
7. A heat pump as claimed in claim 1 wherein said motor and said compressor are mounted within a sealed casing.
8. A heat pump as claimed in claim 7 wherein said compressor is provided with at least one scavenge valve open to the interior of said sealed casing and arranged to maintain said interior at a pressure below the pressure of the working fluid in said compressor.
9. A heat pump comprising an evaporator, a condenser, a pressure control device connected between the outlet from said condenser and the inlet to said evaporator, a compressor connected between the outlet of said evaporator and the inlet to said condenser, an electric motor arranged to drive said compressor and a control system for said motor arranged to enable the speed of said motor to be controlled as desired to adjust the amount of heat transferred from said evaporator to said condenser, wherein said motor comprises a polyphase in-duction motor energised from a DC supply through said control system, and wherein said polyphase motor is provided with one phase terminal per phase and said control system comprises a pair of electrically operable switches for each phase of said load, one switch of each pair being operative to connect the corresponding phase terminal of said load to one terminal of said DC supply and the other switch of each pair being oper-ative to connect the corresponding phase terminal to the other terminal of said DC supply; sequencing means connected to said switches to operate the switches of each pair alternately and to simultaneously operate corresponding switches of all said pairs in sequence; and rate means connected to said sequencing means to control the rate of operation of said sequencing means, whereby the rate of operation of said sequencing means controls the speed of rotation of said motor.
10. A heat pump as claimed in claim 9 wherein said rate means comprises a clock having an adjustable pulse repetition rate.
11. A heat pump as claimed in claim 10 wherein said sequencing means comprises a logic circuit connected to said clock to receive pulses therefrom and having a pair of outputs for each phase of said polyphase motor, the outputs of each pair being complementary; each output comprising a pulse train having a mark space ratio of approximately 50% and a pulse repetition rate directly proportional to the pulse repetition rate of said clock; the outputs of each pair being time displaced relative to each other pair by an integral multiple of a minimum time comprising the period of said pulse train divided by the number of said phases; and each output of every pair of outputs being connected to the corresponding switch of the corresponding pair of switches to operate same.
12. A heat pump as claimed in claim 11 wherein the magnitude of the pulses of said pulse train is modulated to reduce the effective voltage per phase applied to said motor.
13. A heat pump as claimed in claim 9 wherein each of said switch pairs comprises two transistors, one of said transistors being connected to one terminal of said DC supply and the other of said transistors being connected to the other terminal of said DC supply, the corresponding phase terminal being connected in series between said two transistors and all said pairs of switches being connected in parallel to each other.
14. A heat pump as claimed in claim 9 wherein said polyphase motor comprises a polyphase induction motor.
15. A heat pump as claimed in claim 14 wherein the direction of rotation of said motor is reversible by reversing the sequence of operation of said switch pairs.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPD456878 | 1978-06-01 | ||
| AUPD4568 | 1978-06-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094836A true CA1094836A (en) | 1981-02-03 |
Family
ID=3767591
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000328863A Expired CA1139361A (en) | 1978-06-01 | 1979-05-31 | Control system for polyphase loads |
| CA328,862A Expired CA1094836A (en) | 1978-06-01 | 1979-05-31 | Heat pumps |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000328863A Expired CA1139361A (en) | 1978-06-01 | 1979-05-31 | Control system for polyphase loads |
Country Status (13)
| Country | Link |
|---|---|
| JP (2) | JPS558293A (en) |
| CA (2) | CA1139361A (en) |
| CH (1) | CH633393A5 (en) |
| DE (2) | DE2921729A1 (en) |
| DK (2) | DK227079A (en) |
| FR (2) | FR2427564A1 (en) |
| GB (2) | GB2022808B (en) |
| IL (2) | IL57441A (en) |
| IT (2) | IT1121316B (en) |
| NL (2) | NL7904354A (en) |
| NZ (2) | NZ190517A (en) |
| SE (2) | SE7904843L (en) |
| ZA (2) | ZA792500B (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE7907945L (en) * | 1979-09-25 | 1981-03-26 | Bo John Stefan Nystrom | MULTI-PHASE GENERATION DEVICE DEVICE |
| EP0046147A1 (en) * | 1980-08-11 | 1982-02-24 | Heinrich Wächtler | Device for moving liquid mediums, particularly in heat pumps |
| CH660100A5 (en) * | 1981-12-18 | 1987-03-13 | Cerac Inst Sa | DEVICE FOR DRIVING A COMPRESSOR. |
| DE3239284A1 (en) * | 1982-10-23 | 1984-05-03 | DC-Aggregate Engineering AG, 6363 Fürigen | THREE-PHASE ASYNCHRONOUS MOTOR |
| US4734628A (en) * | 1986-12-01 | 1988-03-29 | Carrier Corporation | Electrically commutated, variable speed compressor control system |
| JP3156801B2 (en) * | 1991-10-17 | 2001-04-16 | 本田技研工業株式会社 | Automotive air conditioners |
| JP3267993B2 (en) * | 1991-11-27 | 2002-03-25 | 本田技研工業株式会社 | Air conditioning system for vehicles |
| JP3125198B2 (en) * | 1991-12-04 | 2001-01-15 | 本田技研工業株式会社 | Battery temperature control device for electric vehicle |
| US5927089A (en) * | 1995-11-13 | 1999-07-27 | O'donnell; Dennis W. | Air conditioner for a motor vehicle |
| JP2002243246A (en) * | 2001-02-15 | 2002-08-28 | Sanden Corp | Air conditioner |
| CN106524549A (en) * | 2016-12-01 | 2017-03-22 | 广州华凌制冷设备有限公司 | Constant-frequency air conditioning system and control method thereof |
| CN106969569A (en) * | 2017-03-21 | 2017-07-21 | 合肥美的电冰箱有限公司 | Refrigeration plant control method, system and refrigeration plant |
| CN110108748B (en) * | 2019-06-05 | 2021-09-10 | 安徽理工大学 | Frost heaving experimental device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1486811A (en) * | 1973-09-03 | 1977-09-28 | Nz Inventions Dev Authority | Waveform synthesis using switching circuits |
| JPS5549509B2 (en) * | 1973-12-28 | 1980-12-12 | ||
| SE392766B (en) * | 1974-04-18 | 1977-04-18 | Projectus Ind Produkter Ab | CONSTRUCTION SYSTEM, INCLUDING A HEAT PUMP AND A FUEL-LEADED HEAT BOILER WITH A RADIATOR CIRCUIT |
| DE2459769A1 (en) * | 1974-12-18 | 1976-07-01 | Krupp Gmbh | CONTROL DEVICE FOR THE COOLING CAPACITY IN AN AIR-CONDITIONING SYSTEM OF A TRAIN CARRIAGE |
-
1979
- 1979-05-22 NZ NZ190517A patent/NZ190517A/en unknown
- 1979-05-22 ZA ZA792500A patent/ZA792500B/en unknown
- 1979-05-22 NZ NZ190518A patent/NZ190518A/en unknown
- 1979-05-22 ZA ZA792499A patent/ZA792499B/en unknown
- 1979-05-23 GB GB7917870A patent/GB2022808B/en not_active Expired
- 1979-05-23 GB GB7917871A patent/GB2022942B/en not_active Expired
- 1979-05-29 DE DE19792921729 patent/DE2921729A1/en not_active Withdrawn
- 1979-05-29 DE DE19792921678 patent/DE2921678A1/en not_active Withdrawn
- 1979-05-30 IL IL57441A patent/IL57441A/en unknown
- 1979-05-30 IL IL57442A patent/IL57442A/en unknown
- 1979-05-31 DK DK227079A patent/DK227079A/en unknown
- 1979-05-31 DK DK226979A patent/DK226979A/en unknown
- 1979-05-31 CA CA000328863A patent/CA1139361A/en not_active Expired
- 1979-05-31 CA CA328,862A patent/CA1094836A/en not_active Expired
- 1979-05-31 IT IT23163/79A patent/IT1121316B/en active
- 1979-05-31 IT IT23164/79A patent/IT1121073B/en active
- 1979-06-01 FR FR7914113A patent/FR2427564A1/en not_active Withdrawn
- 1979-06-01 JP JP6759479A patent/JPS558293A/en active Pending
- 1979-06-01 SE SE7904843A patent/SE7904843L/en not_active Application Discontinuation
- 1979-06-01 NL NL7904354A patent/NL7904354A/en not_active Application Discontinuation
- 1979-06-01 SE SE7904842A patent/SE7904842L/en not_active Application Discontinuation
- 1979-06-01 NL NL7904355A patent/NL7904355A/en not_active Application Discontinuation
- 1979-06-01 FR FR7914114A patent/FR2427733A1/en not_active Withdrawn
- 1979-06-01 JP JP6759579A patent/JPS558588A/en active Pending
- 1979-06-01 CH CH514179A patent/CH633393A5/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2427733A1 (en) | 1979-12-28 |
| ZA792500B (en) | 1980-09-24 |
| IL57441A0 (en) | 1979-09-30 |
| GB2022942A (en) | 1979-12-19 |
| IT1121316B (en) | 1986-04-02 |
| IL57442A0 (en) | 1979-09-30 |
| NZ190518A (en) | 1982-12-21 |
| NZ190517A (en) | 1982-12-21 |
| CH633393A5 (en) | 1982-11-30 |
| JPS558588A (en) | 1980-01-22 |
| NL7904355A (en) | 1979-12-04 |
| SE7904843L (en) | 1979-12-02 |
| GB2022808A (en) | 1979-12-19 |
| DK226979A (en) | 1979-12-02 |
| CA1139361A (en) | 1983-01-11 |
| IL57442A (en) | 1983-12-30 |
| GB2022808B (en) | 1982-11-17 |
| IL57441A (en) | 1982-08-31 |
| JPS558293A (en) | 1980-01-21 |
| DE2921729A1 (en) | 1979-12-06 |
| FR2427564A1 (en) | 1979-12-28 |
| IT7923163A0 (en) | 1979-05-31 |
| NL7904354A (en) | 1979-12-04 |
| GB2022942B (en) | 1982-06-09 |
| SE7904842L (en) | 1979-12-02 |
| IT7923164A0 (en) | 1979-05-31 |
| IT1121073B (en) | 1986-03-26 |
| ZA792499B (en) | 1980-08-27 |
| DK227079A (en) | 1979-12-02 |
| DE2921678A1 (en) | 1979-12-06 |
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| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19980203 |