Method and apparatus for controlling an induction motor

• US 6,246,207 B1
• Filed: 12/03/1998
• Issued: 06/12/2001
• Est. Priority Date: 06/26/1998
• Status: Expired due to Fees

• Current Assignee: Regal Beloit America, Inc. (Regal Rexnord Corp.)
• Original Assignee: A. O. Smith Corporation
• Inventors: Dellinger, Stephen J., Rudiak, Jerry A., VanSistine, Thomas G.
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): SMITH, TYRONE W
• Application Number:
  US09/204,594
• Time in Patent Office: 922 Days
• Field of Search: 318/254, 318/439, 318/138, 318/778-818, 307/64
• US Class Current: 318/801
• CPC Class Codes: H02P 25/04 Single phase motors, e.g. capacitor motors

Abstract

A method and apparatus for controlling a motor. The apparatus includes a voltage input; a half-bridge inverter connected the voltage input and to the motor to provide low speed excitation to the motor; and a circuit for selectively electrically connecting the voltage input to the motor and for selectively electrically disconnecting the inverter from the motor.

Claims

1. A controller for an electric motor, said controller comprising:

a voltage input having a first voltage;

a half-bridge inverter connected to said voltage input and to the motor to provide low speed excitation to the motor, said half-bridge inverter generating a second voltage less than said first voltage;

a microcontroller and a pulse width modulator for generating a quadratic voltage-to-frequency relationship for operating the half-bridge inverter; and

a control circuit for electrically connecting the voltage input directly to the motor to provide high speed excitation and for electrically disconnecting said half-bridge inverter from said motor.

2. A controller as set forth in claim 1 wherein said half-bridge inverter includes no more than two power switches.

3. A controller as set forth in claim 1, and further comprising a first relay for connecting the motor to said half-bridge inverter for low speed operation, and a second relay for connecting the motor to said voltage input for full speed operation.

4. A controller as set forth in claim 3, wherein said control circuit comprises timing means for generating a time delay to control said first and second relays in a break-before-make format so that said first and second relays are never closed at the same time.

5. A controller as set forth in claim 4 wherein, when switching from low speed operation to full speed operation, said time delay is approximately one-hundred milliseconds.

6. A controller as set forth in claim 5 wherein, when switching from full speed operation to low speed operation, said time delay is approximately three seconds.

7. A controller for an electric motor, said controller comprising:

a voltage input;

an inverter connected to said voltage input and to the motor to provide low speed excitation to the motor;

a first relay for connecting the motor to said inverter for low speed operation;

a second relay for connecting the motor to said voltage input for fall speed operation; and

a control circuit for electrically connecting the voltage input directly to the motor and for electrically disconnecting said inverter from said motor, said control circuit including timing means for generating a time delay to control said first and second relays in a break-before-make format so that said first and second relays are never closed at the same time.

8. A controller as set forth in claim 7 wherein said inverter is a half-bridge inverter.

9. A controller as set forth in claim 8 wherein said half-bridge inverter includes no more than two power switches.

10. A controller as set forth in claim 7, and further comprising a microcontroller and a pulse width modulator for generating a non-linear voltage-to-frequency relationship for operating said inverter.

11. A controller as set forth in claim 10 wherein said non-linear voltage-to-frequency relationship is a quadratic relationship.

12. A controller as set forth in claim 7 wherein, when switching from low speed operation to full speed operation, said time delay is approximately one-hundred milliseconds.

13. A controller as set forth in claim 7 wherein, when switching from full speed operation to low speed operation, said time delay is approximately three seconds.

14. A controller for an electric motor, said controller comprising:

a voltage input;

an half-bridge inverter connected to said voltage input and to the motor to provide low speed excitation to the motor;

a first relay for connecting the motor to said half-bridge inverter for low speed operation;

a second relay for connecting the motor to said voltage input for full speed operation;

a microcontroller and a pulse width modulator for generating a quadratic voltage-to-frequency relationship for operating said inverter; and

a control circuit for electrically connecting the voltage input directly to the motor and for electrically disconnecting said half-bridge inverter from said motor, said control circuit including timing means for generating a time delay to control said first and second relays in a break-before-make format so that said first and second relays are never closed at the same time, and so that, when switching from low speed operation to fill speed operation, said time delay is approximately one-hundred milliseconds, and, when switching from fill speed operation to low speed operation, said time delay is approximately three seconds.

15. A method of controlling an electric motor using a motor controller, said method comprising:

providing one source of unregulated electrical power selectively connected to the motor through a first relay;

generating a second source of regulated electrical power having a non-linear voltage-to-frequency relationship, the second source being selectively connected to the motor through a second relay; and

selectively switching the relays to connect the motor to the one source for full speed operation, and to the second source for operation of the motor at speeds less than the full speed, wherein said switching includes generating a time delay of approximately one-hundred milliseconds when switching from low speed operation to full speed operation, and generating a time delay of approximately three seconds when switching from full speed operation to speeds less that the full speed.

16. A method as set forth in claim 15 wherein said on source of unregulated electrical power is conventional line power.

17. A method as set forth in claim 15 wherein said generating includes providing a half-bridge inverter connected to said one source of unregulated electrical power.

18. A method as set forth in claim 15 wherein said non-linear voltage-to-frequency is a quadratic relationship.

19. A method of controlling an electric motor using a motor controller, said method comprising:

providing one source of unregulated electrical power selectively connected to the motor through a first relay; and

generating a second source of regulated electrical power having a quadratic voltage-to-frequency relationship, the second source being selectively connected to the motor through a second relay.

20. A method as set forth in claim 19, and refer comprising selectively switching the relays to connect the motor to said one source for full speed operation, and to said second source for operation of the motor at speeds less than the full speed.

21. A method as set forth in claim 20, wherein said switching includes generating a time delay to control said first and second relays in a break-before-make format so that said first and second relays are never closed at the same time.

22. A method as set forth in claim 21, wherein said switching includes generating a time delay of approximately one-hundred milliseconds when switching from low speed operation to full speed operation, and generating a time delay of approximately three seconds when switching from full speed operation to speeds less that the full speed.

23. A method as set forth in claim 19, wherein said one source of unregulated electrical power is conventional line power.

24. A method as set forth in claim 19, wherein said generating includes providing a half-bridge inverter connected to said one source of unregulated electrical power.

25. A method as set forth in claim 24, wherein said half-bridge inverter includes no more than two power switches.

26. A method as set forth in claim 19, wherein said generating further includes providing a microcontroller and a pulse width modulator for generating said quadratic voltage-to-frequency relationship for operating said half-bridge inverter.