JPH01150732A - Cooling compressor driven by brushless dc motor - Google Patents

Abstract

PURPOSE: To rigidly adjust the temp. zone in a comfortable zone by controlling a motor drive in response to an actual velocity of a compressor and temp. error concerning a cooling system. CONSTITUTION: A heat pump 10 has an adjustable speed compressor 14, expansion valve 18 and indoor heat exchanger 20, all continuously connected for circulating a refrigerant through a closely sealed cooling circuit 22. The compressor 14 is driven by a drive unit 27, a motor drive 32 rectifies a motor 28 and this rectification is made electronically in response to a rotor position sensor disposed in the motor. A circuit 48 has a totaling relay 52 for comparing the actual temp. in a comfortable zone with a set point temp. representing desired temp. zone, the totaling relay 52 generates a temp. error signal 58 representing the difference between the zone temp. and its set point. Based on the error signal 58 carrying function parts respectively generate desired cooling and heating compressor speed signals 64, 64'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates generally to refrigeration systems having compressors driven by variable speed motors, and more particularly to refrigeration systems having compressors driven by electronically commutated permanent magnet DC motors. It relates to a cooling system having a compressor.

[Conventional technology]

Temperature control requirements in many cooling systems are very high. This applies to both residential and commercial applications, such as near conditioners and heat pumps, which deal with seasonal changes, humidity changes, daily changes, and even changes in residents. apply. As a result, methods have been developed in the past to vary the capacity of systems to meet that demand. One method, which has emerged as relatively effective and versatile, involves varying the capacity of the system's refrigeration compressor by adjusting its speed.

[Problem to be solved by the invention] The most common method of changing the compressor speed is
It is based on an AC induction motor driven by an inverter. The speed of the compressor changes when the inverter changes the frequency of the current supplied to the compressor motor. Although inverter-driven motors have been used for many years, some of the drawbacks associated with them have not yet been resolved.

Impark requires relatively expensive and large circuitry, and often causes more line interference than other drivers.

Additionally, many inverter-driven induction motors are less effective than variable speed DC motors.

The speed of a typical DC motor is simply varied by changing the magnitude of its DC supply voltage. The motor has a rectifier and brushes that mechanically rectify the DC supply current to synchronize the speed of the motor. Unfortunately, problems arise when using mechanical means to commutate the motor. The brushes wear out and cannot be replaced once they are installed within the closed shell of the refrigeration compressor. Additionally, the current generated between the rectifier and the brushes creates electrical noise and chemical impurities in the refrigerant within the closed shell.

Therefore, to overcome the problems associated with mechanically commutating a motor, permanent magnet brushless DC motors use electronic commutation. The electronic commutation method replaces brushes and rectifiers with an electronic switching device that switches the voltage supplied to the motor's wires in response to rotor position.

The speed of electronically commutated motors is controlled by varying the DC supply voltage in relation to a highly predictable voltage-speed relationship.

However, this relationship changes when it is influenced by the load on the motor. As a result, speed regulation mechanisms based on hypothetical voltage-speed relationships are inappropriate for systems subject to a wide range of loads, such as near conditioners and heat pumps. To make the load on a motor equal to its speed multiplied by its torque,
It also requires a sensor, making it even more expensive.

It is therefore an object of the present invention to respond to the actual speed of the compressor and temperature errors associated with the cooling system when the motor is within its safe operating range, without regard to the actual instantaneous load on that motor. The present invention provides a cooling system having a variable speed compressor driven by an electronically commutated DC motor with a motor drive controlled by the motor driver.

Another object of the present invention is to integrate an electronically commutated motor into a temperature regulation system having multiple feedback control mechanisms including rotor position feedback, compressor speed feedback, and temperature feedback. It is.

Another object of the present invention is to eliminate the high cost and inefficiency associated with inverter driven induction motors.

Another object of the present invention is to eliminate electrical noise commonly associated with mechanical commutators in DC motors.

Yet another object of the invention is to eliminate the use of faulty switches and tachometers inside the hermetic shell of a refrigeration compressor driven by an electronically commutated motor.

Another object of the invention is to provide a cooling system that has both a variable speed compressor and a variable speed fan.

Yet another object of the invention is to provide a heat pump system with a variable speed compressor and a variable speed indoor fan such that the ratio of fan speed to compressor speed is higher for cooling mode than for heating mode. The purpose is to control the speed of

It is another object of the present invention to prevent the compressor from starting and cause the motor to attempt to start in response to unfavorable rotor position and thermodynamic conditions, and to prevent said unfavorable starts between such attempted starts. It is an object of the present invention to provide a cooling system controller that repeatedly changes a state.

Another object of the present invention is to provide the same pulse width adjustment signal (
Pulse-width modulated sig
nal) to divide the speed of the cooling compressor and the speed of the indoor fan by m.

Another object of the present invention is to control a motor drive with a pulse width adjustable control signal such that the motor is stopped when the signal is interrupted.

Another object of the invention is to create a comfort zone by varying the speed of the refrigerant compressor while accurately monitoring the actual speed of the compressor and adjusting the flow of refrigerant through the evaporator by means of an expansion valve. It is necessary to strictly control the temperature of the

These and other objects of the invention will become apparent from the accompanying drawings and the following description of the preferred embodiments.

[Means to solve the problem]

The capacity of this cooling system is varied by varying the speed of a hermetic compressor driven by an electronically commutated brushless DC motor. The capacity and motor speed of this system are regulated by a control system having three interrelated closed loops using three feedback signals.

These feedback signals represent the actual speed of the motor, the rotational position of the rotor and the temperature of the zone regulated by the cooling system.

〔Example〕

FIG. 1 is a schematic diagram of the present invention having a heat pump system 10 controlled by a cooling system controller 12. FIG. The heat pump 10 is a variable speed compressor 14
, an outdoor heat exchanger 16, an expansion valve 18, and an indoor heat exchanger 20, all of which are connected in series to circulate the refrigerant through a hermetically sealed cooling port N22. .

The heat pump system also has a reversing valve 24;
This valve determines the flow direction of the refrigerant flowing through the expansion valve 18 and the side heat exchanger 16.20.

The direction of this flow determines whether the system operates in a cooling or heating mode. Valve 24 places the system in a cooling mode when it is positioned as shown in FIG. In other words, the indoor heat exchanger 20 functions as an evaporator and cooperates with the indoor fan 26 to provide a cooling effect to the comfort zone. To provide a heating effect, valve 2
4 is rotated 90' from the position shown to cause heat exchanger 16 to function as an evaporator and heat exchanger 20 to function as a condenser, thereby placing system 10 in heating mode.

Although the system shown in Figure 1 is a heat pump,
It is also within the scope of the present invention to use a cooling system that operates solely in a cooling mode that does not require the use of reversing valve 24. There are many other variations, such as reversing the direction of rotation of a suitable rotary compressor without using a reversing valve, using a constant speed indoor fan instead of a variable speed indoor fan, or replacing the expansion valve with a capillary or orifice, for example. It is also within the scope of the invention to replace it with any one of a variety of expansion devices such as. However, among these, expansion valves are preferred. This is because it can adjust the flow in response to changing thermodynamic conditions of the refrigerant, such as pressure and heat. The refrigerant circuit 22 shown in FIG. 1 is a schematic diagram, and includes
Although there would normally be an arrangement of two expansion devices and their appropriate bypass check valves, only one expansion device is shown here.

The basic operating principles of heat pumps and other cooling circuits are well known to those skilled in the art and will not be described in detail. However, one feature of the present invention is to adjust the temperature regulation capability of the system 10 by varying the refrigerant compression capability of the compressor. This is done by varying the speed of compressor 14.

The compressor 14 is driven by a variable speed compressor drive 27, which drives its electrical supply 30.
It consists of a permanent magnet plushless direct current motor that receives from a motor drive body 32. The purpose of the motor driver 32 is to electronically commutate the motor 28 and vary its speed by varying the voltage and frequency of the motor's electrical supply 30. Like a normal DC motor, the motor 28
The speed of increases with the height of its supply voltage 34.

The motor driver 32 commutates the motor 28 by alternating the relative polarity of the motor supply voltage 34 and synchronously changing the rotational position and polarity of the motor rotor. Commutation of motor 28 is performed electronically in response to a loaf position sensor located within the motor. The position sensor is, as in the preferred embodiment, electromechanical,
The position feedback signal 36 is generated from within the motor 28 by winding the motor in an unenergized state, or any rotor position sensing device adapted to provide a rotor position feedback signal, such as a proximity switch. This is illustrated by three motor supply lines 40, two of which are energized at a time.

Unenergized winding 3 carrying position feedback signal 36
The supply to the three electric wires 40 is continuously changed as the rotor rotates. Using this method, the number of electrical wires that must pass through the compressor's closed shell can be minimized. This typical motor drive body 3
2 and a description of its basic operating principles, such as the means for sensing rotor position and the means for varying motor speed, are disclosed in U.S. Pat. No. 4,162,435, which is incorporated herein by reference. The motor drive 32 used in the preferred embodiment of the invention is a General Electric Model X-
It is 8794700AHGO3.

Motor driver 32 receives rotor position feedback signal 36
The motor 28 is electronically commutated in response to the motor 28 and the motor supply voltage 34 is controlled in response to the relatively low voltage speed command signal 42. The command signal 42 is electrically isolated from the supply voltage 34 by an optocoupler. A speed command signal 42 having a constant magnitude DC voltage of approximately 5 to 24 volts and having a variable power period is produced by controller 12 comprising a microcomputer circuit 46 and an interface circuit 48. Although the preferred embodiment uses a Mitsubishi 5743 microcomputer, Intel 8751 and 8022 microcomputers are also useful, and a variety of other microcomputers can be used. Circuit 48 provides an interface between microcomputer 46 and various input signals, such as a temperature set point signal 50.

Interface circuit 48 is a relatively uncomplicated circuit and is easily understood from its control diagram shown in FIG. Circuit 48 includes a combination of discrete integrated circuit components. However, it will also be apparent to those skilled in the art that essentially this same circuit can be recreated using only separate electronic components. Circuit 48 includes a summing relay 52 that compares the actual temperature of the comfort zone to a set point temperature representative of the desired zone temperature.

In this preferred embodiment, the zone temperature is determined by the interface circuit 4 by a zone temperature feedback signal 54 generated by a thermistor associated with the comfort zone.
8 and a digital keyboard 56 is used as a means for issuing temperature set point signals 50. However, it will be apparent to those skilled in the art that there are many equally effective means for sensing zone temperature and providing temperature set point signals.

When comparing the zone temperature to its set point, the summation relay 5
2 generates a temperature error signal 58 representing the difference between the zone temperature and its set point. The temperature error signal 58 is sent to a transfer function 60.62, which based on the error signal 58 generates desired compressor speed signals 64.64' for cooling and heating, respectively. The characteristics of the transfer function 60°62 are simply a matter of design choice;
The specific cooling system installation is up to you. A simple example of a useful transfer function is a proportional control that multiplies the temperature error 58 by a gain and then adds a predetermined constant to the resulting product. Other useful transport capabilities include integral control, "PID", look-up tables, or, as in this preferred embodiment, proportional plus integral control.

Depending on the position of the switch 66, one of the desired compressor speed signals 64 or 64'
W M ) is sent to the microcomputer circuit 46 as an input signal. Microcomputer circuit 46
also receives a speed feedback signal 68 representative of the actual speed of compressor 14. There are various means of sensing compressor speed and generating a feedback signal in response. One example is with a generator-type or alternator-type tachometer connected to the compressor or its motor. The tachometer generates a voltage whose amplitude and frequency are proportional to the speed of the compressor. Another example is the use of optical sensors or other types of proximity sensors,
For example, a digital tachometer that counts the revolutions of the rotor in relation to time by using the Hall effect. The method used in this preferred embodiment is such that the drive 27 is connected to the electrical supply 30 in the motor supply line 40.
switching involves counting the electrical pulses generated from within the compressor drive 27 over a period of time.

In response to the desired compressor speed signal 64 or 64' and compressor feedback signal 68, controller 12 generates a PWM speed command signal 42, which controls the speed of compressor 14 according to the function shown in FIG. . In this figure, it can be seen that this function is discontinuous in that the speed command signal 42 is zero when the pulse width is less than a predetermined minimum value of 30% or greater than a predetermined maximum value of 90%. . As a result, compressor 14 shuts down when the wire carrying speed command signal 42 shorts or disconnects. This feature not only provides a simple means of shutting down the compressor, but also provides convenient positioning for installing a series connected trip switch 70 that shuts down the compressor in response to extreme temperatures, pressures, or currents. give. Temperature is monitored at the outer surface of the compressor shell, the terminal box attached to the compressor shell, and the motor drive body 32.
This includes electronic devices, but there are others as well. However, trip switch 70 is connected to speed feedback line 68, which is also a low voltage line carrying 5 to 24 volts.
It can also be positioned in Also, the 30% value and 90% value can be changed to any predetermined value between 0% and 100%.

To issue the speed command signal 42, the controller 12:
It operates according to the algorithm shown in FIG. Upon entering this algorithm, control block 72 determines if there is a motor fault. If there is an error, control is directed to the end of the flowchart where the various timers and counters are blocked. It is reset to zero at 4,76.78. When the end of the program 80 is reached, an automatic interruption begins and the program reenters block 72. This cycle repeats until the motor fault is manually reset, ie, the fault is corrected.

If no motor fault is set, blocks 82 and 84
The variables TRll5PD and C? are respectively indicated by ID5P
D is the initial velocity value, which is zero. TRUSPD is a digital value representing the actual speed of the compressor 14;
CMDSPD corresponds to a speed command signal 42 sent to motor driver 32, which controls the speed of compressor motor 28. The next block 86 starts a speed counter, which continuously counts the pulses that motor driver 32 emits as it commutates motor 28 .

The pulses generated at a frequency proportional to the speed of motor 28 represent the motor speed feedback signal. The compressor speed (TRUSPD) is determined by counting pulses over 0.9 seconds, as indicated by decision block 90. In block 92,
The variable "PULSES" is shown and its value is the last 0.
Represents the number of pulses counted in a 9 second interval. This value is then set to the speed (TRUSPD) in block 94.
) is converted to Block 96.98 resets the 0.9 second timer and speed counter to zero, and the speed counter automatically begins counting another set of pulses to determine the next compressor speed reading.

- Once TRIJSPD is determined, decision block 1
00 and 102 have compressor speeds of 1800 to 720
Determine if you are within a predetermined speed limit of 0 PPM. If not, a speed problem occurs and the extreme speed condition is determined by blocks 142, 144, 146, 148.
Corrective action is performed by either block 50 or blocks 142 and 126. TRUSPD is 1800~7
If it is within 200 PPM, decision block 1
06 causes the speed control action to be performed every 0.2 seconds.

That is, a new commanded speed 11 (CMDSPD) is calculated and supplied to the motor driver 32 to change the speed of the motor 28 every 0.2 seconds. At every 0.2 second interval, the 0.2 second timer is reset to zero by block 108 and the microcomputer circuit 46 receives the desired speed signal 64 or 64' provided by the interface circuit 48.
and gives its digital value to variable 5ETSPD of block 110. Blocks 112 and 114 are 5ET
Limit the SPD value to stay within the range of 1950-6950 RPM. Block 116 is variable 5PD
Set ERR to be equal to RTUSPD - (minus) 5ETSPD.

This represents the difference between the actual compressor speed TRUSPD and the desired speed 5ETSPD. If 5PDERR is within the allowable range, that is, within the dead band, +4 to -
There is no need to change the speed control as shown by decision block 118 with a dead band of 4. Beyond this deadband, CM[1 SPD increases or decreases appropriately in another step, but its new value is limited within the speed limits stored as digital values corresponding to 1800 and 7200 RPM. The calculation of the new value of CMDSPD is performed by control blocks 120, 122, 124, 126, 128, after which control passes to block 130. Block 130 removes the speed error and resets the error counter to zero. Speed errors and counters will be discussed later. The calculated CMDSPD is converted to a PWM signal 42 by block 132 and sent to the motor drive 32 as a result of the block I cock 134, which causes the controller to check whether the compressor 28 is actually operating. Change. This is an external compressor, and the ON' signal is from the microcomputer 46.
This is accomplished by decision block 136, which determines whether the data has been sent to the server.

If the compressor ON signal is not present, CHDSPD
changes to zero at block 138 and the compressor is commanded to stop by blocks 138, 132, and 134. Thereafter, if there is no speed error, control j11 then returns to block 90 through decision block 140. If the compressor ON signal exists,
CMDSPD blocks 122.124, 126.12
8, CMDSPD holds the value calculated by P
WM signal 42, this signal is transmitted to block 132,
The signal is sent to the motor drive body 32 as shown at 134. If no speed error exists, control then returns to block 90.

As mentioned above, the speed problem is determined by decision blocks 100 and 102.
determined by As recognized by decision block 100, if an overspeed condition occurs, decision block 142 directs control to corrective action, ie, causes control block 126 to reduce the compressor speed. However, even if CHDSPD is 180 ORP
Even if M is reduced to the lowest design limit, the overspeed condition still exists.
If the next speed check indicates that the attempt was unsuccessful, such that there is, then decision block 142 directs control to block 144.

Block 144 sets the speed error and block 146 increments the speed error counter. If the value of that counter exceeds a predetermined limit of 10, as shown by block 14B, block 150 sets a motor fault, which causes the compressor to stop. The program again enters block 74.76.78.80,
Begin another interruption. However, the compressor will not start again until the motor fault is manually reset; if the fault counter value is less than 10, block 138 assigns a zero value to CHDSPD, which will stop the compressor. , which is only for a predetermined time delay of 7 minutes, as shown in blocks 140 and 152. , after 7 minutes, the compressor will turn on as long as the compressor ON signal is present.
Automatically restart.

If an underspeed condition exists, as determined by decision block 102, no attempt is made to speed up and the compressor is redirected to or block 144°146.148,15.
Stop via 0. In the event of an underspeed condition, the compressor is immediately shut down to avoid the possibility of tnQ due to inadequate lubrication.

It will be apparent to those skilled in the art that the foregoing algorithm describes the overall control mechanism of the preferred embodiment, and that various hardware and software variations are also within the scope of the invention6, for example: Many parts of the algorithm are easily layered by the microcomputer itself, and blocks 144, 146, 148.15
0, block 152 causes a 7 minute time delay, and block 1
10.134, the digital signal is converted into a pulse-width adjustment signal, or vice versa, and furthermore, the interruption that initiates the control algorithm is made externally, e.g. associated with the interface circuit 48. The control algorithm provides a break for the algorithm of FIG. 3, which provides a break for the sequential circuit 48.

It is also clear that many of the predetermined digital values can be varied, such as those limited to blocks 82, 84, 90, 100, 102, 106° 112.114, 118.148, and that doing so is In some cases it may be preferable.

The aforementioned control mechanisms may also be disabled during a diagnostic modality of the cooling system. In that diagnostic modality, a technician typically takes the signal 42 from the controller 12 and replaces it with a low voltage alternating current signal (25 volts or less) from a readily available source.

A diode in series with the motor driver 32 converts the AC signal into a pulsed DC signal with a constant power period of about 7.50%.

Referring now to FIG. 1, a preferred embodiment of the present invention is shown in which a variable speed indoor fan 26 is connected to a second plasticless DC motor 15 similar to a compressor motor 28.
It can be deformed by driving with 4. Fan motor 154 is electronically commutated by motor drive 156 to vary its speed in response to a second PWM speed command signal 15B issued by controller 12. The speed of fan 26 is controlled as a function of compressor speed, as shown in FIG. Cooling modality function 160 (Figure 4) is provided by input 162 (Figure 1);
The heating mode function 164 (FIG. 4) is input to input 166.
(Figure 1). Style selection switch 16
8 determines which function 160 or 164 to use to calculate the fan speed command signal 158 (similar to a compressor's CMDSPD) to motor drive E 156.

As shown in FIG. 4, functions 160 and 164 have different slopes for purposes, with slope 174 being greater than slope 176. In other words, the ratio of fan speed to compressor speed is greater in the cooling mode than in the heating mode, which means that in the cooling mode, the ratio of the indoor fan air flow rate to the cooling capacity is approximately constant and CFM/ (TOH ratio is constant), the temperature of the indoor airflow is approximately constant in the heating mode.

As shown in FIG. 1, this basic refrigeration system is such that its speed is controlled in response to a PWM speed command signal 42, which is the same signal used to control the speed of compressor 14. Variable speed outdoor fan 17'
It is further modified to include 0.

Although the invention has been described in conjunction with a preferred embodiment, variations thereof will be apparent to those skilled in the art. Accordingly, the scope of the invention is determined by the claims that follow.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the present invention; Fig. 2 is a graph showing the relationship between compressor speed and its control PW11 signal; Fig. 3 is a control algorithm of the present invention; Fig. 4 is a diagram showing the cooling mode and 2 is a graph showing the relationship between indoor fan speed and compressor speed in both heating modalities. [Explanation of symbols] 10... Heat pump system 12... Cooling system controller 14... Variable speed compressor 16... Outdoor heat exchanger 18... Expansion valve 20.
...Indoor heat exchanger 22...Cooling circuit 24...
Reversing valve 27...Variable speed compressor drive device 28...Brushless DC motor 30...Electricity supply body 32...Motor drive body 34...Supply voltage 36...Position feedback signal 38...Windling 40... Supply line 42.
...Speed command signal 46...Microcomputer circuit 48...Interface circuit 50...Temperature set point signal 52...Summing relay section 58...Temperature error signal 60.62...Transfer function section 70... Trip switch 72.120, 122, 124, 126, 128...
Control block 74.76.78...Block 90, 100.102.106.118...Decision block 92.94.96, 98, 108, 110.112
, 114, 126, 142, 144° 146, 148.
150...Block PfT Desired In-layer Fan Distance CFM Tips Play. Speed command PPM (CHDSPC))

Claims (1)

[Claims] 1. a) A compressor, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger arranged in a closed shell, all of which are connected in series to regulate the temperature of the comfort zone. b) a cooling system controller for generating a pulse width adjusted speed command signal in response to a zone temperature set point and the temperature of the comfort zone; and c) a variable speed compressor motor that is controlled in response to a width-adjusted speed command signal such that: i) when the pulse width of said speed command signal is within a predetermined lower pulse width range, said motor is in a non-operational state; ii) the motor is in a non-energized state when the pulse width of the speed command signal is within a predetermined upper pulse width range, and iii) the pulse width of the speed command signal is within the upper range. within a predetermined intermediate range between and the lower range,
a cooling system wherein the speed of the motor is controlled to vary as a function of the pulse width. 2. A variable speed indoor fan associated with the indoor heat exchanger, the speed of the fan changing in response to a second pulse width adjusted speed command signal. cooling system. 3. The system selectively operates in a heating mode or a cooling mode, and the controller controls the speed of the compressor motor and the speed of the indoor fan such that the ratio of fan speed to compressor speed is in the cooling mode. 3. Cooling system according to claim 2, characterized in that the heating mode is larger than the heating mode. 4. The cooling system according to claim 1, wherein the pulse width adjustment speed command signal is a DC signal. 5. The system is selectively operated in a diagnostic mode, and the compressor motor is controlled in response to an AC speed command signal when the cooling system is in the diagnostic mode. Cooling system as described in. 6. The cooling system of claim 1, wherein the pulse width adjusted speed command signal is carried across an optocoupler. 7. The cooling system of claim 1, wherein the pulse width adjustment speed command signal is carried through a trip switch that opens in response to a fault occurring in the cooling system. 8. The cooling system of claim 2, further comprising a variable speed outdoor fan whose speed changes in response to the pulse width adjustment signal. 9.a) A compressor, an outdoor heat exchanger, an expansion device, and an indoor heat exchanger arranged in a closed shell, all of which are connected in series and closed seal cooling to regulate the temperature of the comfort zone. b) a temperature sensor for providing a temperature feedback signal representative of the temperature of said comfort zone; c) a device for providing a temperature set point signal representative of a desired temperature of said zone; and d) driving said compressor. a speed sensing device for sensing the actual rotational speed of a variable speed electric motor and providing a motor speed feedback signal representative of the actual rotational speed of the motor; e) said temperature feedback signal, said temperature set point signal and said motor speed feedback signal; f) a position for sensing the rotational position of a rotor of the motor and for generating a rotor position feedback signal in response to the rotational position; a sensing device; and g) a motor driver for conveying an electrical supply to the motor and adjusting the electrical supply in response to the pulse width adjustment signal and the rotor position feedback signal. 10. Claim 10, wherein the motor driver changes the speed of the motor in response to the pulse width adjustment signal and electronically commutates the motor in response to the rotor position feedback signal. 9. The cooling system according to 9. 11. The motor driver stops the motor by interrupting its electricity supply when the pulse width of the pulse width adjustment signal is smaller than a predetermined minimum width. cooling system. 12. The motor driver stops the motor by interrupting its electricity supply when the pulse width of the pulse width adjustment signal is larger than a predetermined maximum width. cooling system. 13. Cooling system according to claim 9, characterized in that the pulse width adjustment signal is isolated from the motor's electrical supply by an optocoupler. 14. According to claim 9, further comprising a trip switch connected to a low voltage line disconnected from the electrical supply of the motor for interrupting the pulse width adjustment signal in response to a fault occurring in the cooling system. Cooling system as described. 15. The cooling system according to claim 14, wherein the fault is a condition in which the refrigerant pressure reaches a predetermined pressure limit. 16. The cooling system of claim 14, wherein the trip switch is a temperature responsive switch adapted to open in response to sensing a predetermined temperature limit. 17. characterized in that the fault is defined as the current of the electrical supply of the motor exceeding a predetermined current limit;
A cooling system according to claim 14. 18. The system includes a refrigerant through which the thermodynamic state is changed, and further includes a device for attempting to start a compressor driven by the motor, the device including a device for attempting to start a compressor driven by the motor, the device including a refrigerant through which the thermodynamic state is changed. If the motor does not rotate continuously as indicated by the sensing device, cutting off the attempt after a predetermined period of time and automatically waiting another predetermined period before making the next attempt when starting the motor. such that repeated attempts are made to start the motor, causing the motor to rotate continuously; or
the thermodynamic state of the refrigerant and the rotational position of the rotor until the number of unsuccessful start-up attempts reaches a predetermined number indicative of a fault in the system, or the earlier of the two occurs, in any case; 10. Cooling system according to claim 9, characterized in that: can be varied between unsuccessful start-up attempts. 19. Claim 19 further comprising a variable speed fan associated with the indoor heat exchanger, the fan being driven by a brushless DC electric motor whose speed varies in response to a second pulse width adjustment signal. The cooling system according to item 9. 20, further comprising a variable speed outdoor fan whose speed varies in response to the pulse width adjustment signal;
A cooling system according to claim 9. 21. The system is selectively operated in a heating mode or in a cooling mode, and with respect to the speeds of the fan and the compressor, the ratio of fan speed to compressor speed is lower for the cooling mode than for the heating mode. 20. Cooling system according to claim 19, characterized in that the cooling system is larger than the case. 22, a) sensing the temperature of a comfort zone; b) determining a temperature error by comparing the temperature of the comfort zone to a desired zone temperature; and c) inducing a desired compressor speed as a function of the temperature error. d) sensing the actual speed of a refrigeration compressor driven by a variable speed brushless DC electric motor; and e) determining the rotational position of the DC motor rotor by sensing a position feedback signal produced by the unforced windings of the motor. f) electronically commutating the motor in response to the rotary position of the rotor; g) comparing a first digital value representing the desired compressor speed to a second digital value representing the actual compressor speed; inducing a digital command speed value thereby commanding the compressor to operate at a speed in discrete limited increments; h) storing in the microcomputer a third digital value representing the predetermined speed limit; i) recognizing if an extreme speed condition occurs, characterized by the actual speed of the motor reaching a predetermined speed limit; j) if no extreme speed condition exists, the digital instruction changing the speed of the compressor by changing the speed value in discrete increments with limits; k) if extreme speed conditions exist, changing the speed value to the digitally commanded speed value in discrete increments; 1) attempting to correct an extreme speed condition, if the step of attempting to correct an extreme speed condition is unsuccessful, disengaging the motor; 23. The method of claim 22, comprising the step of: using an expansion valve to adjust the flow of refrigerant through the refrigeration system in response to the thermodynamic conditions of the refrigerant. 24. Sensing the actual speed of the compressor includes counting the number of times over time that electronically commutating the motor switches the electrical supply carried to the motor in the plurality of motor supply lines. 23. Method according to claim 22, characterized in that. 25. The method of claim 22, further comprising converting the digital command speed value into a pulse width adjustment signal such that the speed of the compressor changes in response to the pulse width adjustment signal. 26. The method according to claim 25, characterized in that the motor is deenergized when the pulse width of the pulse width adjustment signal is less than a predetermined minimum pulse width. 27. The method according to claim 25, characterized in that the motor is deenergized when the pulse width of the pulse width adjustment signal is greater than a predetermined maximum pulse width. 28. Method according to claim 25, characterized in that the pulse width adjustment signal is isolated from the electrical supply of the motor by an optocoupler. 29. further comprising interrupting the electrical supply to the motor by means of a trip switch responsive to a fault occurring in the cooling system, said trip switch being connected to a low voltage line having a voltage lower than the electrical supply voltage of the motor; 23. A method according to claim 22, characterized in that. 30. The method of claim 29, wherein the trip switch opens in response to sensing a predetermined temperature limit. 31. Method according to claim 29, characterized in that the fault is defined as the refrigerant pressure of the cooling system reaching a predetermined pressure limit. 32. Method according to claim 29, characterized in that the fault is defined as the current of the motor's electrical supply exceeding a predetermined current limit. 33, the refrigeration system includes a refrigerant having a changing thermodynamic state therethrough and further includes a step attempting to start a motor-driven compressor, which is directed by a speed sensing step. If the motor does not rotate continuously, after a certain period of time,
cutting off that attempt, and automatically waiting another predetermined period of time when the motor starts, before making the next attempt, thereby repeatedly attempting to start the motor-driven compressor and starting the motor. The thermodynamic state of the refrigerant and the rotational position of the motor, whichever comes first, until the number of unsuccessful attempts reaches a predetermined number indicating a fault in the system.
23. The method according to claim 22, characterized in that it can vary between unsuccessful startup attempts. 34. The cooling system of claim 25, wherein the cooling system includes an indoor fan associated with an indoor heat exchanger, further comprising varying the speed of the fan in response to a second pulse width adjustment signal. Method described. 35. The method of claim 34, wherein the fan is driven by a second brushless DC motor. 36. The cooling system operates selectively in a heating mode or in a cooling mode, and the compressor and fan are coupled such that the ratio of fan speed to compressor speed is greater in the cooling mode than in the heating mode. 35. A method according to claim 34, characterized in that it comprises the step of varying the speed. 37. The method of claim 25, wherein the cooling system includes an outdoor fan and further comprising varying the speed of the outdoor fan in response to the pulse width adjustment signal. 38. The method of claim 22, wherein the step of attempting to correct an extreme speed condition involves attempting to reduce the speed of the motor to a speed less than a predetermined speed limit. 39. The method of claim 22, wherein the step of attempting to correct an extreme speed condition involves attempting to increase the speed of the motor to a speed greater than a predetermined speed limit. 40, a) an expansion valve regulating the flow of refrigerant through a heat exchanger functioning as an evaporator; b) connected in series with said expansion valve and cooperating with an indoor fan to regulate the temperature of the comfort zone; an indoor heat exchanger; c) an outdoor heat exchanger connected in series with said indoor heat exchanger; and d) a speed thereof that affects its ability to compress a refrigerant conveyed in continuous flow through said indoor heat exchanger. e) a variable speed compressor drive connected to drive said compressor at different speeds to produce different capacities, the compressor drive comprising a motor drive; f) a temperature sensor for sensing the temperature of the comfort zone; g) a device for providing a desired temperature set point in the comfort zone; and h) a drive for the compressor. and the temperature sensor;
a controller electrically connected to said device for setting a desired set point temperature; said controller having first, second and third closed loops interrelated therewith; said motor drive; operating in a control mechanism comprising said DC motor and said temperature sensor; i) said first closed loop comprising: a velocity generated by said controller and conveyed to said compressor drive; a command signal; and an electrical supply sent to the DC motor having a voltage and frequency that varies in response to the speed command signal, whereby the speed of the compressor varies in response to the speed command signal; a temperature regulating effect generated by the cooling system and acting on the comfort zone to regulate its temperature by the indoor heat exchanger cooperating with the indoor fan, and that the temperature regulating effect increases with the speed of the compressor; and a zone temperature feedback signal representative of the temperature of the comfort zone and produced by the temperature sensor, and the zone temperature feedback signal being returned to the controller to influence the speed command signal, thereby controlling the first closed loop. ii) said second closed loop comprises said speed command signal responsive to a speed feedback signal representative of the actual speed of said compressor, said speed feedback signal produced by said compressor driver and transmitted to said controller. iii) the third closed loop is configured to provide feedback from the motor driver to the motor in response to a rotor position feedback signal indicative of the rotational position of a rotor of the motor; the electrical supply being conveyed, the rotor position feedback signal originating from within the motor and being returned to the motor drive, thereby closing the third closed loop; A cooling system that operates under a controlled closed loop. 41. The cooling system of claim 40, wherein the speed command signal is a pulse width adjustment signal. 42. The cooling system of claim 41, wherein the motor is placed in a non-energized state when the pulse width of the pulse width adjustment signal is smaller than a predetermined minimum pulse width. 43. The cooling system of claim 41, wherein the motor is deenergized when the pulse width of the pulse width adjustment signal is greater than a predetermined maximum pulse width. 44. The cooling system of claim 41 further comprising an optocoupler isolating the pulse width adjustment signal from the electrical supply sent to the motor. 45, further comprising a trip switch connected to a low voltage line isolated from the electrical supply for disabling the motor in response to a fault occurring in the cooling system. cooling system. 46. The cooling system of claim 45, wherein the trip switch is connected to carry the speed command signal. 47. The cooling system of claim 45, wherein the trip switch is connected to carry the speed feedback signal. 48. The controller attempts to start the compressor, but sever the attempt after a predetermined period of time if the motor does not rotate continuously, as indicated by the speed feedback signal. , and the controller further agitates the motor by automatically waiting another predetermined period of time before making a next attempt when starting the compressor;
and the thermodynamic state of the refrigerant and the rotor until the motor rotates continuously or until the number of unsuccessful start attempts reaches a predetermined number indicating a system fault, whichever comes first. 41. Cooling system according to claim 40, characterized in that the rotational position of the cooling system can be changed between unsuccessful starting attempts. 49. The indoor fan is driven by a second brushless DC electric motor, the speed of which varies in response to a second pulse width adjustment signal.
The cooling system according to 0. 50. The cooling system selectively operates in a heating mode or a cooling mode, and the fan speed and the compressor speed are such that the ratio of fan speed to compressor speed is higher for the cooling mode than for the heating mode. 50. Cooling system according to claim 49, characterized in that the cooling system is controlled such that the cooling temperature is increased.