Method and apparatus of operating a dynamoelectric machine using DC bus current profile

• US 5,420,492 A
• Filed: 01/14/1993
• Issued: 05/30/1995
• Est. Priority Date: 01/14/1993
• Status: Expired due to Term

• Current Assignee: Nidec Motor Corporation (Nidec Corporation)
• Original Assignee: Emerson Electric Company
• Inventors: Skinner, james L., Sood, Pradeep K., Petty, Douglas M.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Cabeca, John W.
• Application Number:
  US08/004,411
• Time in Patent Office: 866 Days
• Field of Search: 363/37, 363/57, 363/58, 363/139, 318/254, 318/138, 318/439, 318/701, 318/722, 318/723, 318/732, 318/800, 318/807, 318/802, 318/809, 318/803
• US Class Current: 318/809
• 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 6/18 without separate position detecting elements
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A dynamoelectric machine, for example, a brushless permanent magnet motor (M) has a plurality of stator windings (S) and a rotor (T) which rotates with respect to the windings. Apparatus (10) is provided for controlling winding commutation with respect to the rotor. A DC bus (14) supplies current to the windings. The current waveshape has characteristics which are a function of the commutation angle with respect to the windings. Current magnitude and waveshape are sensed by a sensing unit (22) and the sensed waveshape is sampled to obtain commutation information. An inverter (20) successively energizes and de-energizes the respective stator windings. A controller (26) obtains samples of the waveshape, and processes the information obtained by the sampling to control winding commutation. The controller controls the inverter operation to provide a commutation angle which optimizes motor performance and efficiency for a particular set of motor operating conditions. To do this, the processor evaluates slope and amplitude information from the sampled DC bus current waveshape, determines if the waveshape corresponds to a desired waveshape representing a desired commutation angle, and adjusts the commutation frequency produced by the inverter, if necessary, to obtain the desired waveshape.

Claims

1. Apparatus for controlling the commutation angle of a dynamoelectric machine having a plurality of stator windings and a rotor for rotation with respect to said windings, comprising:

power supply means for supplying voltage to the windings, said power supply means having an output supply line and a return supply line;

means for sensing the current waveshape in at least one of the supply lines, said current having a waveshape the relative characteristics of which are a function of the commutation angle whether the commutation be at an optimal in phase angle, or lagging, or leading;

commutation means for successively energizing the respective stator windings; and

,

processor means for deriving commutation angle information from the sensing means and for controlling operation of the commutation means on the basis of the information derived to adjust the commutation angle so it is in phase thereby operating the motor in a stable and efficient manner.

2. The apparatus of claim 1 wherein the power supply means includes a DC bus connected to the motor.

3. The apparatus of claim 2 wherein the sensing means senses the DC bus current waveshape.

4. The apparatus of claim 3 wherein the commutation means includes an inverter interposed between the bus and the motor, the inverter being responsive to control signals from the control means to energize and de-energize the stator windings.

5. The apparatus of claim 4 wherein the sensing means includes a sensor by which the current waveshape is developed.

6. The apparatus of claim 5 wherein the sensing means further includes amplifier means for amplifying the waveshape.

7. The apparatus of claim 5 wherein the processor means includes analog-to-digital conversion means for converting the sensed current waveshape characteristics to corresponding digital values.

8. The apparatus of claim 7 wherein the processor means further includes sampling means for sampling the converted waveshape at at least two points on the current waveshape for each commutation interval, and means for evaluating the two sampled points to determine the commutation angle.

9. The apparatus of claim 8 wherein the processor means further includes control means responsive to said evaluating means to increase or decrease the commutation interval, if the commutation angle is leading or lagging an optimal angle, for operating the motor at its optimal efficiency.

10. The apparatus of claim 1 wherein the control means controls the commutation angle over the entire operating range of the motor.

11. The apparatus of claim 10 wherein the processor means includes a microcontroller.

12. The apparatus of claim 7 wherein the processor means includes waveshape processing means for processing information samples relating to both the current waveshape and amplitude.

13. The apparatus of claim 9 wherein the processor means further includes drive control means for providing a frequency output used by the processor means to produce a control input to the inverter.

14. The apparatus of claim 9 wherein the processor means further includes drive control means for providing a voltage output used by the processor means to produce a control input to the inverter.

15. Apparatus for controlling the commutation angle of a dynamoelectric machine in the form of a motor having a plurality of stator windings and a rotor which rotates with respect to the windings comprising:

a DC bus connected to the motor for supplying current to the windings, said current having a current waveshape the relative characteristics of which are a function of the commutation angle of the motor;

an inverter interposed between the bus and the motor for successively energizing and de-energizing respective ones of the stator winding plurality to commutate the windings in a selected sequence;

means for sensing the current waveshape; and

,

processor means for controlling operation of the inverter to control the commutation angle and optimize the efficiency of the motor throughout its entire range of operation, the processor means including waveshape processor means responsive to the sensing means for sampling the current waveshape to obtain commutation angle information and for evaluating the samples to determine if the commutation angle is at an optimal angle, or leading or lagging the optimal angle, and control means responsive to the evaluation of the samples to increase or decrease the commutation interval of the windings, if the commutation angle is not the optimal angle, thereby to achieve motor efficiency for the input power supplied by the bus and an output load on the motor.

16. The apparatus of claim 15 wherein the sampling means samples the current waveshape at at least two points on the waveshape envelope for each commutation interval.

17. The apparatus of claim 15 wherein the inverter is a pulse width modulated inverter.

18. The apparatus of claim 15 wherein the inverter is a six-step inverter.

19. The apparatus of claim 16 wherein the sensing means includes resistance means across which the current waveshape is developed, and amplifier means for amplifying the sensed waveshape.

20. The apparatus of claim 19 wherein the processor means includes analog-to-digital conversion means for converting sensed waveshape characteristics to corresponding digital values.

21. The apparatus of claim 15 wherein the waveshape processor means includes means for determining the slope of the waveshape.

22. The apparatus of claim 21 wherein the waveshape processor means further includes means for determining the amplitude of the waveshape.

23. Apparatus for controlling the commutation angle of a motor having a plurality of stator windings for each phase and a rotor which rotates with respect to the windings comprising:

a DC bus connected to the motor for supplying current to the windings, said current having a current waveshape whose characteristics are a function of the commutation angle;

an inverter interposed between the bus and the motor for successively energizing and de-energizing the respective stator windings to commutate the windings;

means for sensing the current waveshape; and

,

a microcontroller responsive to the sensing means for sampling the current waveshape at at least two points to obtain commutation angle information, for evaluating the samples to determine if the commutation angle is an optimal angle or leading or lagging the angle, the commutation angle being indicated by the slope of the waveshape as determined by the samples, and for increasing or decreasing the commutation interval based on the evaluation of the samples so the commutation angle is adjusted to the optimal angle for the motor operating conditions.

24. A method of controlling the commutation angle in a dynamoelectric machine comprising:

commutating windings of the machine by systematically energizing and de-energizing them;

sampling a resultant current waveshape, the waveshape having characteristics which are a function of the commutation angle;

obtaining commutation angle information from the sampled current waveshape; and

controlling the commutation angle in response to the information obtained.

25. The method of claim 24 further including sensing the current waveshape;

and,

sampling the sensed waveshape at at least two separate points on the waveshape envelope for each commutation interval.

26. The method of claim 25 wherein controlling commutation includes evaluating the samples to determine if the commutation angle is at an optimal angle for the machine operating conditions, or leading or lagging the optimal angle;

and,

as appropriate, increasing or decreasing the commutation interval to vary the commutation angle until it changes to the optimal angle.

27. A method of controlling the commutation of a brushless permanent magnet motor having a plurality of stator windings and a rotor which rotates with respect to the windings comprising:

supplying voltage from a DC bus to the windings to energize the windings;

commutating the respective stator windings;

sensing the DC bus current waveshape, the waveshape having a relative characteristics which are a function of the commutation angle of the motor;

continuously sampling the sensed waveshape to obtain commutation angle information, the waveshape being sampled at at least two points during each commutation interval;

evaluating the sample information to determine if the instantaneous commutation angle is at an optimal angle or leading or lagging the optimal angle; and

,

increasing or decreasing the commutation interval if the commutation angle is not the optimal angle thereby to achieve motor efficiency for the input power supplied by the bus and an output load on the motor.

28. The method of claim 27 wherein sensing the waveshape includes impressing the winding current on a resistance means to develop the current waveshape, amplifying the waveshape, and performing an analog-to-digital conversion of the waveshape to convert the waveshape characteristics to corresponding digital values.

29. The method of claim 28 including performing the sampling and evaluation steps using a microcontroller;

and,

performing the commutating step using an inverter to which control signals are supplied to control the commutation interval.

30. A method of controlling the commutation of a switched reluctance motor having a plurality of stator windings and a rotor which rotates with respect to the windings comprising:

supplying voltage from a DC bus to the windings to energize the windings;

commutating the respective stator windings;

sensing the DC bus current waveshape, the waveshape having a relative characteristics which are a function of the commutation angle of the motor;

continuously sampling the sensed waveshape to obtain commutation angle information, the waveshape being sampled at at least two points during each commutation interval;

evaluating the sample information to determine if the instantaneous commutation angle is at an optimal angle or leading or lagging the optimal angle; and

,

increasing or decreasing the commutation interval if the commutation angle is not the optimal angle thereby to achieve motor efficiency for the input power supplied by the bus and an output load on the motor.

31. A circuit for controlling a brushless permanent magnet motor including a stationary assembly having a plurality of winding phases associated with it and a rotor assembly mounted for rotation with respect to the stationary assembly, comprising:

a pair of DC lines;

power supply means for supplying a voltage to said DC lines;

commutation means for successively energizing the respective winding phases connected between said DC lines and said phases, said commutations means energizing respective ones of said winding phases at a commutation angle;

means for sensing the current waveshape passing through the winding phases operatively electrically connected in at least one of said DC lines;

means for determining a commutation angle position from said current waveshape; and

means for generating a control signal based on the commutation angle position derived from the sensed current waveshape for controlling the commutation means so as to bring the commutation angle to a desired angle by altering the commutation interval for selected ones of said winding phases.

32. A circuit for controlling a switched reluctance motor including a stationary assembly having a plurality of winding phases associated with it and a rotor assembly mounted for rotation with respect to the stationary assembly, comprising:

a pair of DC lines;

power supply means for supplying a voltage to said DC lines;

commutation means for successively energizing the respective winding phases connected between said DC lines and said phases, said commutations means energizing respective ones of said winding phases at a commutation angle;

means for sensing the current waveshape passing through the winding phases operatively electrically connected in at least one of said DC lines;

means for determining a commutation angle position from said current waveshape; and

means for generating a control signal based on the current waveshape for controlling the commutation means so as to bring the commutation angle to a desired angle by altering the commutation interval for selected ones of said winding phases.

33. Apparatus for controlling the commutation angle of a dynamoelectric machine having a plurality of stator windings and a rotor for rotation with respect to said windings, comprising:

power supply means for supplying voltage to the windings, said power supply means having an output supply line and a return supply line;

means for sensing the current waveshape in at least one of the supply lines, said current having a waveshape the relative characteristics of which are a function of the commutation angle whether the commutation be at an optimal angle, or lagging, or leading, the sensing means including a sensor by which the current waveshape is developed, amplifier means for amplifying the waveshape, and means for converting the sensed current waveshape characteristics to corresponding digital values;

commutation means for successively energizing the respective stator windings; and

,

processor means for deriving commutation angle information from the sensing means and for controlling operation of the commutation means on the basis of the information derived to adjust the commutation angle so it is optional thereby to operate the motor in a stable and efficient manner, the processor means including sampling means for sampling the converted waveshape at at least two points for each commutation interval, means for evaluating the two sampled points to determine the commutation angle and control means responsive to said evaluating means to increase or decrease the commutation interval, if the commutation angle is leading or lagging the optimal angle.

34. The apparatus of claim 33 wherein the processor means includes waveshape processing means for processing information samples relating to both the current waveshape and amplitude, and the processor means further includes drive control means providing either a frequency output or a voltage output used by the processor means to produce a control input to the inverter.

35. Apparatus for controlling the commutation angle of a motor having a plurality of stator windings and a rotor which rotates with respect to the windings comprising:

a DC bus connected to the motor and supplying current to the windings, said current having a current waveshape whose relative characteristics are a function of the motor'"'"'s commutation angle;

an inverter interposed between the bus and the motor and successively energizing and de-energizing respective stator winding to commutate the windings in a desired sequence;

means for sensing the current waveshape; and

,

processor means for controlling operation of the inverter to control the commutation angle and optimize the efficiency of the motor throughout its entire range of operation, the processor means including waveshape processor means having sampling means for sampling the current waveshape at at least two points on the waveshape for each commutation interval, the sampling means being responsive to the sensing means for sampling the current waveshape to obtain commutation angle information and for evaluating the samples to determine if the commutation angle is at an optimal angle, or leading or lagging the optimal angle; and

,

control means responsive to the evaluation of the samples to increase or decrease the commutation interval of the windings, if the commutation angle is not the optimal angle, thereby to achieve motor efficiency.

36. In a dynamoelectric machine having a plurality of individually energized phases, each phase having an associated phase winding to which current is supplied when the phase is energized, and a rotor rotatable with respect to the phase windings, and means for supplying current to the individual phase windings in a controlled sequence for commutation of the machine, the improvement comprising means for evaluating the current waveshape of the current supplied to the windings to determine a commutation angle between the rotor and the phase windings, the evaluating means obtaining a plurality of current measurements during each commutation interval to determine a commutation angle between the rotor and the phase windings, the evaluating means obtaining a plurality of current measurements during each commutation interval of a phase and deriving from the measurements both the amplitude and the slope of the current waveshape, the amplitude and slope of the waveshape indicating whether the commutation angle is a desired in-phase angle, or a leading or a lagging angle, and means responsive to the determination of the commutation angle for controlling operation of the current supply means to adjust the commutation interval for the phases to adjust the commutation angle to the desired in-phase angle for a particular set of machine operating conditions.

37. In a polyphase dynamoelectric machine having a plurality of individually energized phase windings and a rotor which rotates with respect to the windings, current to the phase windings being supplied to the phase windings from a current bus through an inverter controlled by a processor to effect switching between machine phases by selective energization and deenergization of the respective phase windings, sensing means for sensing a bus current waveshape and sampling means for sampling an output of the sensing means to determine the slope of the waveshape, the processor processing waveshape slope information developed by the sampling means to determine by the current waveshape slope whether a commutation angle between the rotor and phase windings is at an optimal angle, or a leading or a lagging angle with respect thereto, the processor controlling a frequency or voltage input to the inverter to effect the timing of the inverter in energizing and deenergizing the respective machine phases to maintain or bring the commutation angle to the optimal angle for a given set of machine operating conditions.

38. A control device for controlling the commutation angle of a motor having a stator assembly including a plurality of windings, and a rotor assembly mounted for rotation with respect to the stator, the motor being connected to a source of D.C. power, comprising:

a DC bus including a pair of lines connected to the motor for supplying current to the windings, and returning current to the DC source, the current in at least one of said pair of lines having a current waveshape dependent upon an operating characteristic of the motor;

an inverter operatively connected between the DC bus and the motor for successfully energizing and de-energizing respective one of said stator windings in a desired sequence, thereby establishing a commutation interval for each winding;

means for sensing the current waveshape in at least one of said lines; and

A processor for controlling operation of the inverter, such that motor efficiency is optimized during motor operation, the processor including a waveshape processor having sampling means for sampling the current waveshape at least two points of the waveshape for each commutation interval, the sampling means being operatively connected to the sensing means and including means for comparing the current waveshape to a desired current waveshape, said processor means controlling the inverter to bring and maintain the current waveshape into correspondence with the desired waveshape based on the waveshape information so obtained.