GB2034989A - Control of DC series motors - Google Patents
Control of DC series motors Download PDFInfo
- Publication number
- GB2034989A GB2034989A GB7935575A GB7935575A GB2034989A GB 2034989 A GB2034989 A GB 2034989A GB 7935575 A GB7935575 A GB 7935575A GB 7935575 A GB7935575 A GB 7935575A GB 2034989 A GB2034989 A GB 2034989A
- Authority
- GB
- United Kingdom
- Prior art keywords
- armature
- current
- field
- controller according
- diversion
- 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.)
- Withdrawn
Links
- 230000003313 weakening effect Effects 0.000 claims abstract description 9
- 238000004804 winding Methods 0.000 claims description 7
- 239000004065 semiconductor Substances 0.000 claims description 5
- 230000001960 triggered effect Effects 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 230000000737 periodic effect Effects 0.000 claims 3
- 238000010304 firing Methods 0.000 claims 1
- 238000007493 shaping process Methods 0.000 claims 1
- 239000003990 capacitor Substances 0.000 description 11
- 101000668165 Homo sapiens RNA-binding motif, single-stranded-interacting protein 1 Proteins 0.000 description 10
- 102100039692 RNA-binding motif, single-stranded-interacting protein 1 Human genes 0.000 description 10
- 230000001419 dependent effect Effects 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009499 grossing Methods 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 101100365087 Arabidopsis thaliana SCRA gene Proteins 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 101150105073 SCR1 gene Proteins 0.000 description 1
- 101100134054 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) NTG1 gene Proteins 0.000 description 1
- 230000001976 improved effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
- H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
- H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
- H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
- H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
- H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
- H02P7/298—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature and field supplies
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Direct Current Motors (AREA)
Abstract
A controller for a DC series motor comprises a main drive thyristor SCR, for controlling armature voltage and a field diversion path R9, T2 for weakening the field, when thyristor bypass S1 is closed, to provide a diverted speed range in excess of the speed range achievable through thyristor control. The degree of field diversion is automatically varied by an armature current sensor to maintain the optimum degree of field diversion despite variations in torque requirement and to maintain armature current approximately constant during the diverted speed range. The armature current is sensed by a magnetoresistive device Hz, compensated for temperature and used to control the frequency of an oscillator whose output controls switch T2 in the diversion path. Amplifier A2 ensures no field weakening for high field voltages. Switch T2 may be a transistor or thyristor. <IMAGE>
Description
SPECIFICATION
Electric motor controller
This invention relates to electric motors, and, in particularto the control of series wound motors by field weakening.
In a typical arrangement, used for example in certain battery powered vehicles, speed control is achieved through a combination of a chopper connected in series with the motor to control armature voltage and a resistive field diversion path which may be connected in parallel with the field winding at low armature currents to weaken the field and thereby increase the motor speed beyond the speed range of the chopper control. When the torque rises, the diversion path is disconnected to prevent armature current rising to unacceptable levels and this
switching in and out of the diversion path as the required torque alters can lead to undesirably abrupt changes in the velocity of the vehicle. It is one object of the invention to provide an improved controller capable of providing smooth speed control.
Accordingly, the present invention consists in a controller for a DC series motor, comprising armature voltage control means operable to control the motor armature voltage in response to a desired motor speed input to the controller; a current path for the diversion of current from the field winding to weaken the motor field; current regulation means for regulating current in said diversion path and armature current sensing means for providing said regulation means with an indication of armature current, whereby the controller is effective at maximum armature voltage and over a range of motor torque requirement to maintain the degree of field weakening at the maximum level consistent with armature current remaining below a predetermined threshold.
Advantageously, the current regulation means comprises repetitively actuable semi-conductor switch means disposed in the diversion path, means for comparing said indication of armature current with a reference and means for varying the mean conducting period of the switch means in accordance with said comparison.
Preferably, the armature current sensing means comprises a magnetoresistive device disposed adjacent the motor armature lead.
Suitably, the controller further comprises means for open-circuiting said diversion path at armature voltages beneath the maximum.
It will be appreciated that the invention provides a controlled motor with the desirable characteristics of high torque at low speeds and increased speed through field weakening in low torque situations, without the hitherto attendant disadvantage of jerky transitions between diverted and non-diverted speed ranges. The correct amount of field diversion is automatically selected for the particulartorque requirement.
The invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure lisa circuit diagram partly in block form of one embodiment of the present invention,
Figure 2 is a circuit diagram again partly in block form of a second embodiment of this invention, and
Figure 3 is a collection of graphs illustrating signals at identified points in the circuit of Figure 2.
Referring to Figure 1, a series wound DC motor has its armature and field connected in series with a drive thyristor SCR, between the battery positive and return rails. The thyristor is provided with conventional control circuitry and with a by-pass contactor S, which can be closed when full armature voltage is required, as an alternative to the thyristor SCR, remaining continuously in the on state.
There are connected in series between the battery positive and return rails, a switch S2, a resistance R, and a Zener diode Z,. Two potential divider chains in the form, respectively of resistance R2 magneto resistive device H, and resistance R4, and resistance
R3, magneto resistive device H2 and resistance R5 are connected in parallel with the Zener diode Z, and the junction between resistances R1, R2 and R3 is further connected through resistance R6 with the noninverting input of an operational amplifier A2. The junction between resistance R2 and magneto resistive device H, is connected to the inverting input of an operational amplifier A, and the non-inverting input of this amplifier is connected to the junction between resistance R3 and magneto resistive device
H2.The output of amplifier A, is taken to the input of a voltage controlled oscillator arranged to provide a square wave output of a frequency inversely dependent upon the output of amplifier A1. The output of the voltage controlled oscillator serves to trigger a monostable which accordingly provides a series of constant width pulses at a repetition rate determined by the frequency of the voltage controlled oscillator. A resistance R7 is provided between the non-inverting input of amplifier A2 and the ground rail and the inverting input of this amplifier is connected with the junction of motor armature and field. A diode D, connects the output of amplifier A2 with the output of the monostable.
A compound arrangement of power transistors T1 and T2 is connected in parallel with the field winding and serves to provide a current diversion path for that field winding. In particular, the junction between armature and field is connected through resistance
R8 with the collector of a first power transistor T1 and through resistance R9 with the collector of a second powertransistorT2. The emitter of transistor T, is connected to the base of transistor T2 and the emitter of transistor T2 is connected to the ground rail. The base of transistor T, receives the output of the monostable.
The operation of the described controller can now be understood. When the motor is in the nondiverted speed range, switches S, and S2-which are ganged or otherwise interconnected-are open and motor speed is determined solely by the control of armature voltage through the action of drive thyristor SCR1. As is conventional, switch S, is closed automatically if the SCR control receives a desired motor speed input corresponding with maximum armature voltage to avoid the drive thyristor remaining permanently in the conducting state. In the circuit according to this invention, closure of switch S, serves also to close switch S2 thus energizing the
field weakening circuitry.
Magneto resistive device H2 is disposed in a suit
able iron core at position H in Figure 1,the motor
armature lead passing through this core. The resistance of device H2 is accordingly dependent upon
armature current. Matched magneto resistive device
H, is sufficiently distant from the armature lead to be unaffected by the magnetic field generated thereby and the operational amplifier A, accordingly receives a differential input which is an indication of armature
current independent of temperature variations affecting the resistance of devices H, and H2 equally.
The frequency of the square wave generated by the voltage controlled oscillator falls from a maximum as the armature current-and accordingly the output of amplifier A,-rises. Accordingly, at low armature current, the monostable will provide pulses at a rapid repetition rate and the compound transistor arrangement will be substantially continually in the conducting state.Current will be diverted from the motor field winding to a degree determined by the choice of resistors R6 and Rg and the motor will reach top speed. Ifthetorque requirement for the motor rises, armature current will rise and the frequency of the voltage controlled oscillator will fall, the monostable will accordingly provide pulses at a slower repetition rate and the field diversion path will conduct only intermittently. The mean value of the current diverted from the field winding will fall, the motor speed will decrease and the armature current will tend to return to its original value. In practice, the feedback parameters of the described circuit are
arranged so that in operation the motor armature
current remains substantially constant.
The function of amplifier A2 is to act as a safety
device since if the field voltage becomes excessively
high, the output of the amplifier will be driven low so turning off transistor T and open-circuiting the field diversion path. It is not possible therefore in the described circuit for the field to be weakening whilst the motor is under significant load.
A second embodiment of this invention is illustrated in Figure 2. A series wound DC motor is connected with its armature and field in series with a drive thyristor SCR, between the battery positive and return rails. The drive thyristor is provided with control circuitry of conventional form and with a by-pass contactor S, as described above with reference to
Figure 1. A field diversion path comprising the series connection of a diversion resistance R, and a diversion thyristor SCR2 is connected in parallel with the motorfieldwinding and the drive thyristor SCR,.
Opposite ends of a length of cable or a shunt X in series with the armature are connected respectively through resistors R1, and R" with inputs of an operational amplifier A,. Zener diodes Z2 and Z2 are connected between the respective inputs and the return rail to prevent the input voltages to the amplifier from rising to battery positive when the motor is not
in operation and smoothing capacitors C1 and C2 connected in parallel with the respective Zener
diodes serve to reduce any ripple or noise. Resistors R12 and R12 serve to connect the respective inputs of
amplifier A, with the battery positive rail.The output
of amplifierA, is connected with the input of a voltage controller oscillator arranged to provide a
square wave output the frequency of which is
dependent upon the amplifier output. A monostable circuit is triggered by the output of the voltage controller oscillator to provide pulses at a repetition rate which is dependent upon the amplifier output.
A Zener diode Z4 and resistor R14 are connected in series between the battery positive and return rails and a smoothing capacitor C2 is connected in parallel with the Zener diode. The junction between resistor R,3 and Zener diode Z4 is connected through resistor R,s with the collector of a transistor T2 and is connected directly with the emitters of two further transistors T4 and 7;;. The emitter of transistor T2 is connected to the return rail and the base of this transistor is connected through resistor R16 with the return rail and through capacitor C4 with the output of the monostable. Transistor Ts has its base connected via capacitor C5 with the collector of transistor T2 and the base of this transistor is also connected through resistor R,7 with the transistor emitter. Transistor T4 has a resistor R,8 connected between its base and emitter and has its base also connected through capacitor C6 with the output of the monostable.
A commutating capacitor C7 for the diversion thyristor SCR2 is connected in series with an inductive resistance R,g and a charging thyristor SCR2 between the battery positive and return rails. The positive plate of the commutating capacitor C7 is connected to the cathode of the diversion thyristor
SCR2 via a commutating thyristor SCR4. The collector of transistor Ts is connected to the gate of the charging thyristor SCR2 through resistor R20 and diode D2, and to the gate of diversion thyristor SCR2 through resistance R21 and diode D2. Diode D4 and resistor R22 serve to connect the gate of commutating thyristor
SCR4 with the collector of transistor T4.
The operation of the described circuit can be best understood with reference to the graphs of Figure 3.
Vx is the voltage across the shunt X and is thus an indication of the armature current. Graph A shows the output of amplifier At which is the amplified inverse of Vx. Graph B shows the output of the voltage controlled oscillator which is a square wave the frequency of which is determined by the amplifier output and is thus inversely proportional to armature current. Graph C shows the output of the monostable as a series of pulses with a fixed pulse width and a repetition rate determined by the frequency of the voltage controlled oscillator. Graphs D and E show the outputs of differentiating circuits C4, R,6 and C6 R18 respectively and it will be seen that NPN transistor T3 is turned on at the leading edges of the monostable output to provide a series of negative going pulses shown in Graph F, whilst PNP transistorT4 is turned on atthe pulse trailing edges to provide a series of positive going pulses shown in
Graph K which have the identical repetition rate of those shown in Graph F but which are displaced by an amount equal to the pulse width of the monostable. PNP transistor Ts serves to invert the negative
going pulses shown in Graph F to provide a series of
positive going pulses shown in Graph H.
The pulses shown in Graph H fire the diversion thyristor SCR,2 to open the field diversion path and also charging thyristor SCR2 to initiate charging of commutating capacitor C7. R,g is inductive so that
SCR2 will self-commutate when the capacitor C7 is fully charged. After the fixed interval determined by the pulse width of the monostable, the pulses shown in Graph K fire commutating thyristor SCR4 to connectthe positive plate of the charged commutating capacitor C7 with the cathode of the diversion thyristor SCR2 thereby to commutate that thyristor. It will be appreciated that the charging thyristor SCR2 must remain in the conducting state for a sufficient length of time to permit full charging of capacitor C7 (see
Graph L) and the pulse width of the monostable must be chosen accordingly.The voltage shown in
Graph M is of course a measure of the diverted field current and it will be seen that the mean value of the diverted current rises as the armature current fails.
As with the embodiment described above with reference to Figure 1,the circuit parameters are preferably arranged so that the armature current remains substantially constant in the diverted speed range.
A particular application of the circuits shown above in Figures 1 and 2 is in the control of the traction motors in battery powered vehicles such as industrial trucks. Afoot pedal speed control for the truck would be coupled with the control circuitry of the drive thyristor and full depression of the foot pedal control would close the by-pass contactor. It is preferred that closure of this contactor serves to energize the field diversion circuitry (as in Figure 1) although if desired circuits according to the invention could be arranged to provide field weakening when the speed of the motor is being controlled through the drive thyristor. In either case, when the truck is in the diverted speed range and encounters for example an incline, the increase torque requirement will automatically result in the degree of field current diversion being reduced to a level which is the maximum level consistent in the new circumstances with armature current remaining below a chosen threshold. Throughout the diverted speed range, the degree of field diversion is automatically maintained at the optimum level for the imposed torque requirement.
Claims (14)
1. A controller for a DC series motor, comprising armature voltage control means operable to control the motor armature voltage in response to any desired motor speed input to the controller; a current path for the diversion of current from the field winding to weaken the motor field; current regulation means for regulating current in said diversion path and armature current sensing means for providing said regulation means with an indication of armature current, whereby the controller is effective at maximum armature voltage and over a range of motortorque requirement to maintain the degree of field weakening at the maximum level consistent with armature current remaining below a predetermined threshold.
2. A controller according to Claim 1, wherein the current regulation means comprises repetitively actuable semi-conductor switch means disposed in the diversion path, means for comparing said indication of armature current with a reference and means for varying the mean conducting period of the switch means in accordance with said comparison.
3. A controller according to Claim 2, therein the means for varying the mean conducting period of the semi-conductor switch means comprises a voltage controlled oscillator arranged to provide a periodic output the frequency of which is determined by said comparison.
4. A controller according to Claim 3, wherein the semiconductor switch means comprises a power transistor arrangement.
5. A controller according to Claim 4, wherein the means for varying the mean conducting period of the switch means further comprises a monostable triggered by said periodic output to supply pulses at a repetition rate determined by armature current to a base input of the power transistor arrangement.
6. A controller according to Claim 3 wherein the semiconductor switch means comprises a thyristor arrangement.
7. A controller according to Claim 6, wherein the means for varying the mean conducting period of the switch means comprises a monostable triggered by said periodic output to supply pulses at
a repetition rate determined by armature current and pulse shaping circuitry arranged to provide thyristor firing and commutating pulses on the leading and trailing edges respectively of the monostable pulses.
8. A controller according to any one of the preceding claims, wherein there is provided means for open circuiting the field diversion path at excessive field voltages.
9. A controller according to any one of the preceding claims wherein the current regulation means is arranged so to vary the diverted field current as to maintain armature current sensibly constant during field diversion.
10. A controller according to any one of the preceding claims, wherein there is provided means for disabling the current regulation means at armature voltages beneath the maximum.
11. A controller according to any one of the preceding claims, wherein the armature current sensing means comprises a magneto resistive device disposed adjacent the motor armature lead.
12. A controller according to Claim 2 wherein the armature sensing means and the means for supplying said reference comprise respective like magneto resistive devices only one of which is sensitive to the magnetic field generated by the armature lead.
13. A controller according to any one of the preceding claims, for use with the traction motor of a battery powered vehicle.
14. A controller for a DC series motor substantially as hereinbefore described with reference to and as shown in Figure 1 or Figure 2 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7935575A GB2034989A (en) | 1978-10-12 | 1979-10-12 | Control of DC series motors |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7840317 | 1978-10-12 | ||
| GB7935575A GB2034989A (en) | 1978-10-12 | 1979-10-12 | Control of DC series motors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2034989A true GB2034989A (en) | 1980-06-11 |
Family
ID=26269163
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7935575A Withdrawn GB2034989A (en) | 1978-10-12 | 1979-10-12 | Control of DC series motors |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2034989A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2633788A1 (en) * | 1988-05-26 | 1990-01-05 | Linde Ag | METHOD AND INSTALLATION FOR ATTENUATING FIELD IN SERIES-TYPE ELECTRIC MACHINES OF ELECTRICALLY DRIVEN VEHICLES AND CIRCUIT FOR IMPLEMENTING THE METHOD |
| WO1991015379A1 (en) * | 1990-04-06 | 1991-10-17 | Sevcon Limited | Speed control system |
| GB2254740A (en) * | 1991-04-09 | 1992-10-14 | Yang Tai Her | Motor control |
| EP0991180A2 (en) * | 1998-09-30 | 2000-04-05 | AKO-Werke GmbH & Co. KG | Method and circuit for speed control of an universal dc motor |
| GB2484740A (en) * | 2010-10-23 | 2012-04-25 | Technelec Ltd | High efficiency power supply |
-
1979
- 1979-10-12 GB GB7935575A patent/GB2034989A/en not_active Withdrawn
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2633788A1 (en) * | 1988-05-26 | 1990-01-05 | Linde Ag | METHOD AND INSTALLATION FOR ATTENUATING FIELD IN SERIES-TYPE ELECTRIC MACHINES OF ELECTRICALLY DRIVEN VEHICLES AND CIRCUIT FOR IMPLEMENTING THE METHOD |
| WO1991015379A1 (en) * | 1990-04-06 | 1991-10-17 | Sevcon Limited | Speed control system |
| GB2254740A (en) * | 1991-04-09 | 1992-10-14 | Yang Tai Her | Motor control |
| EP0991180A2 (en) * | 1998-09-30 | 2000-04-05 | AKO-Werke GmbH & Co. KG | Method and circuit for speed control of an universal dc motor |
| EP0991180A3 (en) * | 1998-09-30 | 2002-08-14 | Diehl AKO Stiftung & Co. KG | Method and circuit for speed control of an universal dc motor |
| GB2484740A (en) * | 2010-10-23 | 2012-04-25 | Technelec Ltd | High efficiency power supply |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |