Detection of faults in the working of electric motor driven equipment

• US 5,754,450 A
• Filed: 06/17/1996
• Issued: 05/19/1998
• Est. Priority Date: 09/06/1993
• Status: Expired due to Fees

• Current Assignee: Diagnostics Temed Limited
• Original Assignee: Diagnostics Temed Limited
• Inventors: Solomon, Alan David, Gelman, Efim
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US08/605,156
• Time in Patent Office: 701 Days
• Field of Search: 324/545, 324/772, 361/23, 361/24, 361/30, 361/31, 361/87, 361/94, 364/480, 364/481, 364/483, 364/485, 364/550, 364/551.01, 340/679, 340/680
• US Class Current: 702/35
• CPC Class Codes: G01M 15/00 Testing of engines

Abstract

Apparatus for monitoring the functioning of motor driven equipment, including current sensing apparatus connectable to the power input of the motor and producing a current signal; signal correction apparatus receiving as input the current signal and operative to demodulate the current signal, filter the current signal to retain low frequencies thereof, and convert the current signal from analog to digital form and producing a corrected signal; a memory; a controller in operative connection with the memory, receiving the corrected signal, and having a calibration state and an operation state, and operative, when in the calibration state, to compute the calibration norm of the corrected signal based partly on data contained in the memory and to store the calibration norm in the memory and operative, when in the operation state, to compute the operation norm of the corrected signal based partly on data contained in the memory and to compare the operation norm with the stored calibration norm and to produce a function signal indicating the functioning of the motor driven equipment; and an indicating unit receiving as input the function signal and producing an output indication of the functioning of the motor driven equipment.

Claims

1. Apparatus for monitoring the functioning of motor driven equipment comprising:

current sensing apparatus connectable to the power input of the motor and producing a current signal;

signal correction apparatus receiving as input said current signal and operative to demodulate said current signal, filter said current signal to retain low frequencies thereof, and convert said current signal from analog to digital form and producing a corrected signal;

a memory;

a controller in operative connection with said memory, receiving said corrected signal and having a calibration state and an operation state and operative, when in the calibration state, to compute the calibration norm of said corrected signal based partly on data contained in said memory and to store said calibration norm in said memory and operative, when in the operation state, to compute the operation norm of said corrected signal based partly on data contained in said memory and to compare said operation norm with said stored calibration norm and to produce a function signal indicating the functioning of said motor driven equipment; and

an indicating unit receiving as input said function signal and producing an output indication of the functioning of said motor driven equipment.

2. Apparatus according to claim 1, wherein the current sensing apparatus comprises a current transformer.

3. Apparatus according to claim 1, wherein the current sensing apparatus comprises a magnetic amplifier.

4. Apparatus according to claim 1, wherein the current sensing apparatus comprises a shunt.

5. Apparatus according to claim 1 wherein the motor driven equipment comprises a fan.

6. Apparatus according to claim 1 wherein the motor driven equipment comprises a rotating member and wherein the controller is operative to detect the rate of rotation of the rotating member.

7. Apparatus according to claim 1, wherein the indicating unit comprises a display.

8. Apparatus according to claim 1, wherein the indicating unit comprises an alarm.

9. Apparatus according to claim 1 wherein the signal correction apparatus comprises low pass filter apparatus operative to filter said current signal to retain low frequencies thereof, and

wherein the low pass filter apparatus comprises a Butterworth filter.

10. Apparatus according to claim 1 wherein the signal correction apparatus comprises A-D conversion apparatus operative to convert said current signal from analog to digital form, and

wherein the A-D conversion apparatus has at least 6 bits.

11. Apparatus according to claim 10 wherein the A-D conversion apparatus has at least 8 bits.

12. Apparatus according to claim 1, wherein the motor driven equipment comprises an air conditioning unit and the controller is operative to detect a first defect comprising insufficient refrigerant pressure.

13. Apparatus according to claim 12 wherein the controller is also operative to detect at least one additional defect.

14. Apparatus according to claim 1, wherein the motor driven equipment comprises a chiller and the controller is operative to detect a first defect comprising clogging of an air filter.

15. Apparatus according to claim 14 wherein the controller is also operative to detect at least one additional defect.

16. Apparatus according to claim 1 wherein the motor driven equipment comprises a heat pump.

17. Apparatus according to claim 16 wherein the heat pump has a plurality of modes of heating and the controller is operative to detect the mode of heating of the heat pump.

18. Apparatus according to claim 1 wherein the motor driven equipment comprises refrigeration equipment.

19. Apparatus according to claim 18 wherein the refrigeration equipment comprises evaporator coils and wherein the controller is operative to detect the growth of frost on the evaporator coils.

20. Apparatus according to claim 1 wherein the motor driven equipment comprises a fluid pump.

21. Apparatus according to claim 20 wherein the controller is operative to detect faults in the pump.

22. Apparatus according to claim 20 wherein the controller is operative to detect the rate of flow of the fluid.

23. Apparatus according to claim 22 wherein the controller is also operative to control the operation of the pump.

24. Apparatus according to claim 1 wherein the signal correction apparatus comprises demodulating apparatus operative to demodulate said current signal, and

wherein the demodulating apparatus comprises an active rectifier.

25. A method for monitoring the functioning of motor driven equipment comprising:

sensing the current in the power input of the motor and producing a current signal;

demodulating said current signal, filtering said current signal to retain low frequencies thereof, and converting said current signal from analog to digital form and producing a corrected signal;

receiving said corrected signal, retrieving at least one stored corrected signal from said memory and comparing said corrected signal with said stored corrected signal and producing a function signal indicating the functioning of said motor driven equipment;

receiving said corrected signal and having a calibration state and an operation state and, when in the calibration state, computing the calibration norm of said corrected signal based partly on stored data and storing said calibration norm and, when in the operation state, computing the operation norm of said corrected signal based partly on stored data and to comparing said operation norm with said stored calibration norm and producing a function signal indicating the functioning of said motor driven equipment; and

receiving said function signal and producing an output indication of the functioning of said motor driven equipment.