Motor controls, refrigeration systems and methods of motor operation and control

• US 5,376,866 A
• Filed: 03/26/1993
• Issued: 12/27/1994
• Est. Priority Date: 06/24/1974
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Erdman, David M.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/038,135
• Time in Patent Office: 641 Days
• Field of Search: 318/138, 318/254, 318/439, 318/430, 318/431, 318/432, 318/433, 318/434, 361/23, 361/24, 361/30, 361/31, 361/33, 361/51, 361/90, 361/91, 361/92
• US Class Current: 318/400.1
• CPC Class Codes: F23N 2233/04 with variable speed
• CPC Class Codes: F23N 3/082 using electronic means
• CPC Class Codes: F25B 2600/021 Inverters therefor
• CPC Class Codes: F25B 49/025 Motor control arrangements
• CPC Class Codes: G05D 23/19 characterised by the use of electric means G05D23/1393 takes precedence
• CPC Class Codes: H02K 29/06 with position sensing devices H02K29/03 takes precedence
• CPC Class Codes: H02K 29/10 using light effect devices
• CPC Class Codes: H02P 2209/07 Trapezoidal waveform
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 6/14 Electronic commutators
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers

Abstract

A method of operating a brushless motor having a stationary assembly with at least two different energizable windings for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields. The method includes the steps of simulating rotor position in accordance with the back emf condition of at least one winding, energizing a selected one of the windings in accordance with the simulated rotor position, sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time. An electrically commutated motor controller apparatus controls and speed of a variable speed motor compressor driven by an electrically commutated motor. A controller circuit includes a circuit for producing feedback signals representative of a back emf of the motor. A compressor speed circuit generates actual compressor speed signals for the feedback signals produced by the controller circuit. A duty cycle generator produces a speed controller signal as a function of the actual compressor speed signals, and the speed control signal is transmitted to the controller circuit for adjusting the speed of the electrically commutated motor driven compressor. Other motor controls, refrigeration systems and methods of control and operation are also disclosed.

Claims

1. A method of operating a brushless motor having a stationary assembly with at least two different energizable windings for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields, the method comprising the steps of:

simulating rotor position in accordance with the back emf condition of at least one winding;

selectively energizing the windings in accordance with the simulated rotor position;

sensing an underspeed condition when the motor speed is less than a minimum value for a length of time; and

preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time.

2. A method as set forth in claim 1 wherein the sensing step includes sensing a voltage related to the motor speed in a circuit having a time constant and wherein the length of time is a function of the time constant.

3. A method as set forth in claim 1 further comprising the step of resuming energization of the motor windings when a reset time has elapsed.

4. A method as set forth in claim 1 wherein said step of sensing an underspeed condition includes the steps of repeatedly producing a pulse when each of the windings is to be commutated, filtering the pulses so produced to develop a direct current voltage which is substantially proportional to the motor speed, and providing a signal when the direct current voltage is less than an electrical level representative of the minimum level of the motor speed.

5. A method as set forth in claim 4 wherein said step of repeatedly producing a pulse includes the steps of integrating the back emf until a triggering point is reached and then supplying the pulse.

6. A method of operating a brushless motor having a stationary assembly with at least two windings energizable from a voltage source for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields, the method comprising the steps of:

simulating rotor position in accordance with the back emf condition of at least one winding;

selectively energizing the windings from the voltage source in accordance with the simulated rotor position;

sensing an undervoltage condition when the voltage source provides a voltage that is less than a minimum value; and

preventing energization of any of the windings when the undervoltage condition is sensed.

7. A method as set forth in claim 6 wherein the step of sensing the undervoltage condition includes the steps of voltage dividing the voltage provided by the voltage source to produce a fraction thereof, providing a reference voltage and voltage dividing the reference voltage to supply a value that is a fraction of the reference voltage, and producing an output indicative of presence of the undervoltage condition when the fraction of the voltage provided by the voltage source is less than the value that is a fraction of the reference voltage.

8. A method as set forth in claim 6 further comprising the steps of sensing an overvoltage condition when the voltage source provides a voltage that is greater than a maximum value, and preventing energization of any of the windings when the overvoltage condition is sensed.

9. A method as set forth in claim 8 further comprising the steps of sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time.

10. A method as set forth in claim 6 further comprising the steps of sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time.

11. A method as set forth in claim 6 wherein the simulating step includes integrating the back emf and producing an output when a triggering point is reached to effect commutation of the windings.

12. A method of operating a brushless motor having a stationary assembly with at least two windings and energizable from a voltage source for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields, the method comprising the steps of:

determining the back emf condition of at least one winding;

simulating rotor position in accordance with the determining back emf condition of said at least one winding;

selectively energizing the windings with a voltage from the voltage source in accordance with the simulated rotor position as defined by the determined back emf;

sensing an overvoltage condition when the voltage is greater than a maximum value; and

preventing energization of any of the windings when the overvoltage condition is sensed.

13. A method as set forth in claim 12 wherein the step of sensing the overvoltage condition includes the steps of voltage dividing the voltage provided by the voltage source to produce a fraction thereof, providing a reference voltage and voltage dividing the reference voltage to supply a value that is a fraction of the reference voltage, and producing an output indicative of presence of the overvoltage condition when the fraction of the voltage provided by the voltage source is greater than the value that is a fraction of the reference voltage.

14. A method as set forth in claim 12 further comprising the steps of sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time.

15. A method as set forth in claim 12 wherein the simulating step includes integrating the back emf and producing an output when a triggering point is reached to effect commutation of the windings.

16. A control system for a brushless motor for energization from a voltage source for the motor, the motor having a stator with windings and a rotor mounted for rotation relative to the stator, comprising:

a circuit for generating an input signal corresponding to the presence of the rotor at one of a plurality of predetermined rotary positions with respect to the stator;

electrically controllable switches connected to the windings to control the flow of current therethrough;

an electronic control responsive to the input signal for controlling in a closed loop running mode the switches to commutate the windings of the motor after receipt of the input signal, said electronic control also being responsive to the speed of the motor, and operative to start the motor in a starting mode by controlling the switches to commutate the windings at an increasing rate, and then to shift commutation to the running mode once the motor reaches a predetermined speed, said electronic control being operative to determine the commutation rate as a function of the voltage applied to the motor.

17. The control system as set forth in claim 16 further comprising a power control for variably supplying the voltage for the motor, wherein said electronic control includes regulator means for supplying a control output to said power control, whereby the level of the voltage for the motor is controlled so that the stator windings are energized to a level established by said regulator means.

18. The control system as set forth in claim 16 wherein said electronic control comprises means for increasing the motor speed to a running speed in excess of the predetermined speed of commutation shift.

19. The control system as set forth in claim 16 further comprising a motor current sensor, wherein said electronic control includes means responsive to said motor current sensor for varying the commutation by said electronically controllable switches as a function of the motor current.

20. The method for controlling a brushless motor for energization from a source of voltage for the motor, the motor having a stator with windings and a rotor mounted for rotation relative to the stator, with electrically controllable switch means connected between the source and the windings to control the flow of current therethrough, the method comprising the steps of:

determining an increasing rate of commutation as a function of the voltage applied to the motor;

starting the motor in a starting mode by controlling the switch means to commutate the windings at the determined increasing rate;

once a predetermined motor speed has been reached, shifting commutation from said starting mode to a running mode of operation;

generating an input signal corresponding to the presence of the rotor at one of a plurality of predetermined rotary positions with respect to the stator; and

controlling the switch means to commutate the windings of the motor after the input signal is generated.

21. A method as set forth in claim 20 further comprising the step of regulating the voltage for the motor as a function of the speed of the motor.

22. A method as set forth in claim 20 further comprising the step of increasing the commutation of the windings in frequency in the running mode so that the speed of the motor increases from the predetermined speed to a running speed.

23. A method as set forth in claim 20 further comprising the step of varying the energization of said motor windings as a function of the current in the motor.

24. A control system for an electronically commutated motor adapted to be energized from a source of voltage and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, the control system comprising:

an electronic commutation circuit including switches responsive to control signals and operable generally for electronic commutation of at least some of the winding stages of the electronically commutated motor by applying the voltage thereto in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly; and

a circuit for generating control signals for said electronic commutation circuit, said circuit for generating variably establishing a time interval between commutations as a decreasing function of the voltage applied to the motor, for repeatedly producing in a start mode the control signals for said electronic commutation circuit at the interval variably established, and for shifting commutation to a running mode once the time interval decreases to a predetermined amount.

25. The control system as set forth in claim 24 further comprising a power control for variably supplying the voltage for the motor, wherein said circuit for generating control signals also includes regulator means for supplying at least one control signal to said power control, whereby the voltage for the motor is controlled so that the stator windings are energized to a level established by said regulator means.

26. The control system as set forth in claim 24 further comprising a motor current sensor, wherein said circuit for generating the control signals includes means responsive to said motor current sensor for varying the energization of the electronically commutated motor as a function of the motor current.

27. A method of operating a control system for an electronically commutated motor adapted to be energized from a source of voltage and including a stationary assembly having a plurality of winding stages adapted to be electronically commutated in at least one preselected sequence, and a rotatable assembly associated in selective magnetic coupling relation with the winding stages, the method comprising the steps of:

electronically commutating at least some of the winding stages of the electronically commutated motor in response to control signals by applying the voltage thereto in the at least one preselected sequence to effect the energization of the electronically commutated motor and the rotation of the rotatable assembly;

establishing a variable time interval between commutations as a decreasing function of the voltage applied to the motor;

producing in a start mode the control signals with the variable time so established; and

shifting commutation to another mode once the time interval decreases to a predetermined amount.

28. A brushless motor system for energization from a voltage source, comprising a brushless electric motor having a stationary assembly with a plurality of windings adapted to be energized through electronic commutation in at least one preselected sequence, and a rotor in selective magnetic coupling relation with said windings;

at least one circuit element that generates a position signal corresponding to the presence of said rotor in at least one predetermined rotary position with respect to said stationary assembly;

switches connected to said windings to control the flow of current therethrough; and

an electronic control responsive to said position signal for controlling said motor in a closed loop running mode with said switches to commutate said winding in response to said position signal, said electronic control also being responsive to the speed of said motor and operative to provide a starting mode to start Said motor by controlling said switches to commutate said windings at an increasing rate and shifting said commutation from said starting mode to said running mode when said motor reaches a predetermined speed, said electronic control being operative to determine the commutation rate as a function of the voltage applied to said motor.