Offset PWM signals for multiphase motor

• US 7,193,388 B1
• Filed: 02/02/2006
• Issued: 03/20/2007
• Est. Priority Date: 02/02/2006
• Status: Active Grant

• Current Assignee: Emersub Cxiii Incorporated (Emerson Electric Company)
• Original Assignee: Emerson Electric Company
• Inventors: Skinner, James L., Green, Charles E. B.
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US11/346,027
• Time in Patent Office: 411 Days
• Field of Search: 318/811, 318/810, 318/807
• US Class Current: 318/811
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H02P 2205/01 Current loop, i.e. comparison of the motor current with a current reference

Abstract

A multi phase motor includes a switching array for interconnecting a power source to each phase. A current sensor senses current supplied from the power source via the switching array to the winding and a controller generates offset PWM signals for controlling the switching array to supply power to each of the phases of the winding. The offset timing allows the individual phase currents to be determined from a single current sensor.

Claims

1. An apparatus for supplying current from a power source to each phase of a multi-phase motor comprising:

a switching array interconnecting the power source and each phase of the multi-phase motor;

a current sensor for sensing current supplied from the power source via the switching array to the motor; and

a controller for generating pulse width modulated (PWM) signals for controlling the switching array to supply power to each of the phases of the motor, wherein the PWM signals supplied by the controller to the switching array to supply power to each of the phases is offset a preset amount from the PWM signals supplied by the controller to the switching array to supply power to the other phases.

2. The apparatus of claim 1 wherein the motor is a three phase motor and wherein the offset between each of the three phases is approximately 120 degrees.

3. The apparatus of claim 1 wherein the current sensor comprises a single current sensor for sensing current supplied to the switching array.

4. The apparatus of claim 1 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is in synchronization with a frequency of the PWM signals.

5. The apparatus of claim 1 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is independent of a frequency of the PWM signals.

6. The apparatus of claim 1 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at fixed points with respect to the PWM signals.

7. The apparatus of claim 6 wherein said A/D converter samples the analog signals at or as a function of a leading edge, a trailing edge or a center of each of the PWM signals.

8. An apparatus for supplying current from a power source to first, second and third phases of a motor comprising:

A first switching array interconnecting the power source and the first phase of the motor;

A second switching array interconnecting the power source and the second phase of the motor;

A third switching array interconnecting the power source and the third phase of the motor;

a current sensor for sensing current supplied by the power source to the switching arrays; and

a controller for generating first PWM signals for controlling the first switching array to supply power to the first phase of the motor, generating second PWM signals for controlling the second switching array to supply power to the second phase of the motor, generating third PWM signals for controlling the third switching array to supply power to the third phase of the motor, wherein each of the PWM signals supplied by the controller to each switching array are offset a preset amount from the PWM signals supplied by the controller to other switching arrays.

9. The apparatus of claim 8 wherein the motor is a three phase motor and wherein the offset between each of the three phases is approximately 120 degrees.

10. The apparatus of claim 8 wherein the current sensor comprises a single current sensor for sensing current supplied to the switching array.

11. The apparatus of claim 8 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is in synchronization with a frequency of the PWM signals.

12. The apparatus of claim 8 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is independent of a frequency of the PWM signals.

13. The apparatus of claim 8 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at fixed points with respect to the PWM signals.

14. The apparatus of claim 13 wherein said A/D converter samples the analog signals at or as a function of a leading edge, a trailing edge or a center of each of the PWM signals.

15. A motor comprising:

a multi-phase winding;

a switching array for interconnecting a power source to each phase of the multi-phase winding;

a current sensor for sensing current supplied from the power source via the switching array to the winding; and

a controller for generating PWM signals for controlling the switching array to supply power to each of the phases of the winding, wherein the PWM signals supplied by the controller to the switching array to supply power to each of the phases is offset a preset amount from the PWM signals supplied by the controller to the switching array to supply power to the other phases.

16. The apparatus of claim 15 wherein the motor is a three phase motor and wherein the offset between each of the three phases is approximately 120 degrees.

17. The apparatus of claim 15 wherein the current sensor comprises a single current sensor for sensing current supplied to the switching array.

18. The apparatus of claim 15 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is in synchronization with a frequency of the PWM signals.

19. The apparatus of claim 15 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at a sampling rate which is independent of a frequency of the PWM signals.

20. The apparatus of claim 15 further comprising an A/D converter converting an analog signal from the current sensor into a digital signal supplied to the controller, said A/D converter sampling the analog signal at fixed points with respect to the PWM signals.

21. The apparatus of claim 20 wherein said A/D converter samples the analog signals at or as a function of a leading edge, a trailing edge or a center of each of the PWM signals.