MOTOR CONTROLLER SYSTEM AND METHOD FOR MAXIMIZING ENERGY SAVINGS

• US 20100013427A1
• Filed: 09/10/2008
• Published: 01/21/2010
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: Paul H. Kelley
• Original Assignee: Powerwise Group, Inc.
• Inventors: Kelley, Paul H.
• Granted Patent: US 8,810,190 B2
• Time in Patent Office: Days
• US Class Current: 318/812
• CPC Class Codes: H02P 23/0004 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
• CPC Class Codes: H02P 23/0077 Characterised by the use of a particular software algorithm
• CPC Class Codes: H02P 23/02 specially adapted for optimising the efficiency at low load
• CPC Class Codes: H02P 23/08 Controlling based on slip frequency, e.g. adding slip frequency and speed proportional frequency
• CPC Class Codes: H02P 23/14 Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
• CPC Class Codes: H02P 23/26 Power factor control [PFC]
• CPC Class Codes: H02P 25/24 Variable impedance in stator or rotor circuit
• CPC Class Codes: H02P 29/02 Providing protection against overload without automatic interruption of supply protection against faults of stepper motors H02P8/36
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

A motor controller (4) and method for maximizing the energy savings in an AC induction motor (3) at every load wherein the motor is calibrated at two or more load points to establish a control line (6), which is then programmed into a non-volatile memory (30) of the motor controller. A DSP-based closed-loop motor controller observes the motor parameters of the motor such as firing angle/duty cycles (23), voltage (37), current (9) and phase angles to arrive at a minimum voltage necessary to operate the motor at any load along the control line. The motor controller performs closed-loop control to keep the motor running at a computed target control point, such that maximum energy savings are realized by reducing voltage through pulse width modulation.

Claims

1. A system for controlling an AC induction motor to maximize energy savings compromising:

a means for connecting a motor controller to an AC induction motor;

a means for placing a load on said AC induction motor;

a means for removing a load from said AC induction motor;

a means for sweeping a control space of the AC induction motor and taking measurements of operating parameters of the AC induction motor;

a means for establishing a control line from said measurements;

a means for storing said control line in said motor controller;

a means for controlling said operating parameters; and

a means for performing closed-loop control of said AC induction motor to keep the motor running in accordance with said control line.

2. The system of claim 1 further comprising:

a means for placing said AC induction motor in a fully loaded configuration.

3. The of claim 1 further comprising:

a means for placing said AC induction motor in a fully unloaded configuration.

4. The system of claim 1 further comprising:

measuring a current of said AC induction motor.

5. The system of claim 4 wherein:

the current measurement of the AC induction motor is accomplished by a digital signal processor.

6. The system of claim 1 further comprising:

measuring phase angles of the AC induction motor.

7. The system of claim 6 wherein:

the phase angles measurements of the AC induction motor are accomplished by a digital signal processor.

8. The system of claim 1 further comprising:

a means for controlling a firing angle/duty cycle of said AC induction motor.

9. The system of claim 8 wherein:

said means for controlling said firing angle/duty cycle of said AC induction motor is accomplished by a digital signal processor.

10. The system of claim 1 wherein:

said means for sweeping the control space of the AC induction motor and observing and measuring said operating parameters is accomplished by varying root square means motor voltage of the AC induction motor.

11. The system of claim 10 wherein:

said means for varying the root square means motor voltage of the AC induction motor is a digital signal processor.

12. The system of claim 1 wherein:

said means for establishing a control line from said measurements is accomplished by a digital signal processor.

13. The system of claim 1 wherein:

said means for storing said control line in said motor controller is a non-volatile memory.

14. The system of claim 1 wherein:

said means for performing closed-loop control of said AC induction motor to keep the motor running in accordance with said control line is a digital signal processor.

15. The system of claim 1 wherein:

said means for performing closed-loop control of said AC induction motor to keep the motor running in accordance with said control line is pulse width modulation.

16. The system of claim 15 wherein:

said pulse width modulation is performed using at least one TRIAC driver.

17. The system of claim 15 wherein:

said pulse width modulation is performed using at least one SCR driver.

18. The system of claim 15 wherein:

said pulse width modulation is performed using at least one IGBT driver.

19. The system of claim 15 wherein:

said pulse width modulation is performed using at least one MOSFET driver.

20. The system of claim 1 further comprising:

a means for clamping voltage of the motor at maximum voltage.

21. The system of claim 1 further comprising:

a means for preventing said AC induction motor to run at voltages below minimum voltage.

22. The system of claim 1 further comprising:

a means for determining virtual neutral as a reference.

23. The system of claim 1 further comprising:

a means for detecting zero-crossings of positive and negative halves of a current waveform in said AC induction motor.

24. The system of claim 23 wherein:

said means for detecting zero-crossings of positive and negative halves of a current waveform is at least one window comparator.

25. The system of claim 24 wherein:

a positive voltage is provided to the at least one window comparator as a reference for a positive half cycle;

a negative voltage is provided to the at least one window comparator as a reference for a negative half cycle;

signals form the at least one window comparator pass through an OR gate to create composite current zero-cross digital signals.

26. The system of claim 1 further comprising:

a means for protecting against stalling in said AC induction motor.

27. The system of claim 26 wherein:

a DSP actively controls said AC induction motor while constantly sweeping said AC induction motor for increases in motor current;

said DSP turns motor voltage to full on when an increase in motor current is detected; and

said DSP reduces the motor voltage to follow a control line after current returns to a lower level.

28. A method for controlling an AC induction motor to maximize energy savings comprising the steps of:

a. connecting a motor controller to an AC induction motor;

b. sweeping a control space of the AC induction motor and observing and measuring operating parameters of the AC induction motor throughout the control space;

c. establishing a control line for said AC induction motor from said parameters;

d. storing said control line in said motor controller;

e. controlling the operating parameters along the control line; and

f. performing closed-loop control of said AC induction motor to keep the motor running in accordance with said control line.

29. The method of claim 28 wherein step b comprises:

placing said AC induction motor in a fully loaded configuration;

determining said AC induction motor'"'"'s fully loaded point;

placing said AC induction motor in a fully unloaded configuration; and

determining said AC induction motor'"'"'s fully unloaded point.

30. The method of claim 28 further comprising:

connecting the AC induction motor'"'"'s fully loaded and fully unloaded point to establish the control line of the motor.

31. The method of claim 28 further comprising a step after step d of:

increasing firing angle/duty cycle of the AC induction motor from eighty degrees to one-hundred-fifty degrees and recording current and phase angles along the control line.

32. The method of claim 28 further comprising a step of:

recording current and phase angles along the control line.

33. The method of claim 28 wherein step e comprises:

controlling the operating parameters of voltage along the control line using pulse width modulation.

34. The method of claim 28 wherein:

said pulse width modulation is performed using at least one TRIAC driver.

35. The method of claim 32 wherein:

said pulse width modulation is performed using at least one SCR driver.

36. The method of claim 32 wherein:

said pulse width modulation is performed using at least one IGBT driver.

37. The method of claim 32 wherein:

said pulse width modulation is performed using at least one MOSFET driver.

38. The method of claim 28 wherein step e further comprises:

clamping the operating parameters of voltage at minimum voltage and not allowing said AC induction motor to run at voltages below minimum voltage.

39. The method of claim 28 further comprising a step after step b of:

determining virtual neutral for use as a reference.

40. The method of claim 28 further comprising a step after step b of:

detecting zero-crossings of positive and negative halves of a current waveform in said AC induction motor.

41. The method of claim 40 wherein:

a positive voltage is provided to at least one window comparator as a reference for a positive half cycle;

a negative voltage is provided to the at least one window comparator as a reference for a negative half cycle;

signals form the at least one window comparator pass through an OR gate to create composite current zero-cross digital signals.

42. The method of claim 28 further comprising a step after step f of:

protecting against stalling in said AC induction motor.

43. The method of claim 42 wherein:

a DSP actively controls said AC induction motor while constantly sweeping said AC induction motor for increases in motor current;

said DSP turns motor voltage to full on when an increase in motor current is detected; and

said DSP reduces the motor voltage to follow a control line after current returns to a lower level.