Pulse width modulating motor controller

• US 5,489,831 A
• Filed: 09/16/1993
• Issued: 02/06/1996
• Est. Priority Date: 09/16/1993
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Harris, William A.
• Primary Examiner(s): SALATA, ANTHONY J
• Application Number:
  US08/122,872
• Time in Patent Office: 873 Days
• Field of Search: 318/700, 318/701, 318/254, 318/138, 318/439, 388/804, 388/805, 388/515, 388/815, 388/819, 388/840, 388/911, 388/912, 388/917, 388/930
• US Class Current: 318/701
• CPC Class Codes: H02P 25/08 Reluctance motors
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence

Abstract

A pulse width modulation controller particularly useful for a variable speed variable torque electric motor. Inputs to the controller are a desired RPM signal, a motor electrical signal which is a function of the RPM of the rotor of the motor and its angular position relative to the stator, and a torque feed back signal derived from the power phase winding circuits of the motor. The controller produces pulse width modulated power drive signals which are applied to power switches of the power phase winding circuits of the motor to allow electric current to flow through the power phase winding circuits when power phase enable signals produced by the controller sequentially enable the power switch of a power phase winding circuit to do so. The duty cycle of the power drive signals is a function of the difference between the desired and actual RPM of the motor and the torque of the motor. The frequency of the power drive signals is a fixed integral multiple of the frequency of the power phase enable signals over the full operating range of RPMs of the motor.

Claims

1. A pulse width modulation controller for an electric motor having a rotor, a stator, and a plurality of power phase (winding) circuits with each power phase circuit including a power switch, and means for producing a motor electrical (Me) signal which is a function of the revolutions per minute (RPM) of the rotor of the motor and its position relative to the stator of the motor;

comprising;

circuit means responsive to the Me signal produced by the motor for producing a pulse width modulation signal;

circuit means for producing power phase commutation signals the frequency of which has a fixed relationship to the frequency of said pulse width modulation signal, one power phase enable signal for each power phase winding circuit of the motor;

circuit means for producing a speed error signal, said speed error signal being a function of the difference between the actual RPM of the rotor and a desired RPM; and

pulse width modulation (PWM) circuit means for producing power drive signals for application to the power switch of each of the power phase winding circuits when each power switch is enabled by a power phase enable signal to receive said power drive signals, the frequency of the power drive signals produced by said PWM circuit means being that of the pulse width modulation signal, and the duty cycle of the power drive signals being a function of the speed error signal and of a power phase feedback signal produced by a power phase winding circuit when a power drive signal is applied to the power switch to energize said circuit, said power phase winding circuits being energized in sequence.

2. The pulse width modulation controller of claim 1 in which the fixed relationship between the power phase commutation signal and the frequency of the pulse width modulation signal is that the frequency of the power phase commutation signal is equal to 1/n times the frequency of the pulse width modulation signal and "n" is a positive integer.

3. The pulse width modulation controller of claim 2 in which the electric motor is a variable reluctance motor having a rotor with "R" poles where "R" is an even integer and ME frequency equals the RPM of the rotor multiplied by R.

4. The pulse width modulation controller of claim 3 in which each power phase winding includes means for producing a power phase feedback signal.

5. The pulse width modulation controller of claim 1 in which the electric motor is a permanent magnet motor.

6. A pulse width modulation controller for an electric motor having a rotor, a stator, and a plurality of power phase winding circuits with each power phase circuit including a power switch, and means for producing a motor electrical (Me) signal which is a function of the revolutions per minute (RPM) of the rotor of the motor and its position relative to the stator of the motor;

comprising;

circuit means responsive a Me signal produced by the motor for producing a pulse width modulation signal;

circuit means for producing a power phase commutation signal the frequency of which is 1/n times the frequency of said pulse width modulation signal, where "n" is an integer greater than one;

circuit means to which the said phase commutation signal is applied for producing power phase enable signals, one power phase enable signal for each power phase winding circuit of the motor;

circuit means for producing a speed error signal, said speed error signal being a function of the difference between the actual RPM of the rotor and a desired RPM; and

a plurality of pulse width modulation (PWM) circuit means, each of the PWM circuit means being associated with one of the power phase winding circuits of the motor and for producing for its associated power phase winding circuit a power drive signal for application to the power switch of its associated power phase winding circuit when a power phase enable signal is applied to one of said PWM circuit means, the frequency of the power drive signals produce by said PWM circuit means being that of the pulse width modulation signal, and the duty cycle of the power drive signals being a function of the speed error signal and of a power phase feedback signal produced by each power phase winding circuit when a power drive signal is applied to the power switch of a power phase winding circuit to energize said circuit, said power phase winding circuit being energized in sequence to cause the rotor of the motor to rotate.

7. The pulse width modulation controller for a variable speed variable torque electric motor of claim 6 in which the rotor of the motor has "R" poles and the stator has "S" poles, where "R" and "S" are even integers, and the power phase winding circuits are positioned on the stator poles.

8. The pulse width modulation controller for a variable speed variable torque electric motor of claim 7 in which the electric motor is a variable reluctance motor and the frequency of Me equals the RPM of the rotor multiplied by R.

9. The pulse width modulation controller for a variable speed variable torque electric motor of claim 8 in which the integer "n" equals 5.

10. The pulse width modulation controller for a variable speed variable torque electric motor of claim 8 in which the electric motor is a permanent magnet motor.

11. A pulse width modulation motor controller for a variable speed and variable torque electric motor including a stator having a first set of "S" diametrically opposed stator poles, a rotor mounted within the stator for rotation about an axis of rotation, said rotor having a second set of "R" diametrically opposed rotor poles, where "S" and "R" are even integers, each pair of diametrically opposed poles of one of the set of poles having a series connected power phase winding, means for producing a pulsed motor electrical (Me) signal the timing of the pulses of which is a function of the angular position of the rotor with respect to the stator, the frequency of which is a function of the revolutions per minute (RPM) of the rotor, and the number of rotor poles;

power switch means connected in series with each of the power phase windings for permitting electrical current to flow through a power phase winding in response to a power on portion of a pulse of a power drive signal being applied to the switch means thereof; and

circuit means connected to each of the power phase windings for producing a current feed back signal which is a function of the current flowing through any of the power phase windings at any instant in time;

said motor controller comprising;

first circuit means to which is applied the Me signal for producing a pulse width modulation (PWM) signal which is in phase with the Me signal, and a second signal that is a function the RPM of the rotor of the motor;

second circuit means to which is applied the voltage that is a function of the RPM of the rotor produced by the first circuit means, and a speed set voltage which is a function the desired RPM of the rotor for producing a speed error signal;

third circuit means to which is applied the PWM signal produced by the produced by the first circuit means for a power phase commutation signal, the frequency of which is 1/n times the frequency of the PWM signal applied thereto, where "n" is a positive integer greater than one;

fourth circuit means to which is applied the power phase commutation signal produced by the third circuit means for producing power phase enable signals, one for each power phase winding of the motor; and

PWM current control and power switch logic means, one for each power phase winding of the motor to each of which is applied the speed error signal, the PWM signal, and to each of them respectively a power phase enable signal and a power phase current feed back signal, each of the PWM current control and power switch logic means for producing a pulse width modulated power drive signal having a duty cycle and a frequency the duty cycle of which is a function of the speed error signal and the current feed back signal and the frequency of which is "n" times the power phase enabling signal for application respectively to the power switch means connected in series with each power phase winding of the motor to control the electrical current flow sequentially through each of the power phase windings to cause the rotor to rotate.

12. The pulse width modulation motor controller of claim 11 in which a series connected power phase winding is placed around each pair of diametrically opposed stator windings.

13. The pulse width modulation motor controller of claim 12 in which "S" is greater than "R".

14. The pulse width modulation motor controller of claim 13 in which the first circuit means is a phase-locked-loop device.

15. The pulse width modulation motor controller of claim 14 in which the fourth circuit means is an up/down counter.

16. The pulse width modulation motor controller of claim 15 in which the electric motor is a variable reluctance motor.

17. The pulse width modulation motor controller of claim 15 in which the electric motor is a permanent magnet motor with permanent magnets positioned on the rotor.

18. A pulse width modulation controller for a switched reluctance motor;

said motor having a stator having eight diametrically opposed stator poles;

a rotor mounted within the stator for rotation about an axis of rotation, said rotor having six diametrically opposed rotor poles;

each pair of diametrically opposed stator poles having a series connected power phase winding forming four stator power phase windings;

means for producing a motor electrical (Me) signal the timing of the pulses of which is a function of the angular position of the rotor with respect to the stator, and the frequency of which is a function of the revolutions per minute (RPM) of the rotor multiplied by the number of rotor poles;

power switch means connected in series with each of the stator phase windings for controlling flow of electrical current through each power phase winding in response to a power on portion of each pulse of a power drive signal applied to the switch means thereof; and

circuit means connected to the stator power phase windings for producing a torque feedback signal which is a function of the current flowing through a stator power phase winding at any instant in time;

said controller comprising;

circuit means to which is applied a speed set voltage which is a function a desired RPM of the rotor of the motor and an actual speed voltage which a function of the actual RPM of the rotor of the motor for producing a speed error signal;

a divide by "n" counter circuit having an input terminal and an output terminal;

phase-locked loop (PLL) circuit means including a first signal input terminal to which is applied the Me signal produced by the motor controlled by the controller, a phase comparator input terminal, and a voltage-controlled oscillator (VCO) which produces a pulse width modulation (PWM) signal;

circuit means for applying the PWM signal produced by the VCO to the input terminal of the divide by "n" counter circuit, the divide by "n" counter circuit producing power phase commutation signals at its output terminal;

circuit means for connecting the output terminal of the divide by "n" counter to the phase comparator input terminal of the PLL;

an up/down counter circuit to which is applied the power phase commutation signals for producing power phase enable signals for each of the power phase windings of the motor;

PWM duty cycle control means to which is applied the speed error signal and the torque feedback signals produced by the motor for varying the duration of the power on portion of each pulse of the PWM signal as a function of the difference between the speed error signal and the torque feedback signals for producing PWM power drive signals, the frequencies of which are the same as the frequency of the PWM signal at the VCO output terminal of the PLL; and

logic and power switch control circuit means to which is applied the PWM power drive signals from the PWM duty cycle control means and the phase enable signal produced by the divide by "n" counter for applying PWM power drive signals to the power circuit means of the motor to energize the phase winding sequentially and in synchronization with the rotation of the rotor.

19. The pulse width modulation controller of claim 18 in which "n" is a positive integer.

20. The pulse width modulation controller of claim 19 in which "n" equals five.