Pump controller

• US 6,534,947 B2
• Filed: 01/12/2001
• Issued: 03/18/2003
• Est. Priority Date: 01/12/2001
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated, Sta-Rite Industries LLC (Pentair Plc (Ireland))
• Original Assignee: Sta-Rite Industries LLC (Pentair Plc (Ireland))
• Inventors: Johnson, Steven A., Walker, Dee R., Larson, Kip M.
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): San Martin, Edgardo
• Application Number:
  US09/760,276
• Publication Number:
  US 20020093306A1
• Time in Patent Office: 795 Days
• Field of Search: 318/782, 318/789, 318/103, 318/62, 318/452, 318/453, 318/454, 318/455, 318/484, 361/23, 361/28, 361/30, 361/2, 361/3, 417/12, 417/43
• US Class Current: 318/782
• CPC Class Codes: H02H 3/382 involving phase comparison between current and voltage or between values derived from current and voltage
• CPC Class Codes: H02H 7/0833 for electric motors with control arrangements
• CPC Class Codes: H02P 27/16 using ac to ac converters without intermediate conversion to dc H02P27/05 takes precedence

Abstract

A method and apparatus for controlling an electric motor pump. The method includes the acts of providing an AC power signal having a positive half cycle and a negative half cycle, measuring the voltage of the AC power signal and generating a first two-state output signal that is in a logic high state when the measured voltage is on the positive half cycle and that is in a logic low state when the measured voltage is on the negative half cycle, and measuring the current of the AC power signal and generating a second two-state output signal that is in logic high state when the measured current is on the positive half cycle and that is in a logic low state when the measured current is on the negative half cycle. The method also includes determining a time difference between the first and second two-state output signals, calculating a phase difference based on the time difference, comparing the phase difference to a predetermined threshold value, opening a switch if the determined phase difference is equal to or greater that the predetermined threshold value, and, after the switch is opened, closing the switch after a predetermined amount of time has elapsed.

Claims

1. A method of controlling an electric motor pump, the method comprising:

providing an AC power signal having a positive half cycle and a negative half cycle;

measuring the voltage of the AC power signal and generating a first two-state output signal that is in a logic high state when the measured voltage is on the positive half cycle and is in a logic low state when the measured voltage is on the negative half cycle;

measuring the current of the AC power signal and generating a second two-state output signal that is in a logic high state when the measured current is on the positive half cycle and is in a logic low state when the measured current is on the negative half cycle;

determining a phase difference based on a time difference between the first two-state output signal and the second two-state output signal;

comparing the phase difference to a predetermined threshold value;

opening a switch if the determined phase difference is equal to or greater than the predetermined threshold value; and

closing the switch after a predetermined amount of time has elapsed.

2. A method as claimed in claim 1, further comprising waiting for a predetermined period of time prior to the act of opening a switch.

3. A method as claimed in claim 1, wherein the acts of measuring the voltage, measuring the current, determining a time difference, comparing the determined phase difference, and opening a switch are repeated after the act of closing the switch.

4. A method as claimed in claim 1, further comprising converting the AC power signal to a DC power signal.

5. A method as claimed in claim 4, further comprising providing the DC power signal to a programmable device.

6. A method as claimed in claim 1, further comprising providing the first and second two-state output signals to a programmable device.

7. A pump control apparatus comprising:

a voltage filter capable of being coupled to an AC power source and of generating a first two-state output signal;

a current filter capable of being coupled to an AC power source and of generating a second two-state output signal;

a power supply circuit capable of producing a DC power signal;

a controller coupled to the voltage filter, the current filter, and the power supply circuit and operable to produce a control signal based on the time differential between the first and second two-state output signals; and

a switch coupled to the controller and operable to open in response to the control signal.

8. An apparatus as claimed in claim 7, wherein the switch includes a relay.

9. An apparatus as claimed in claim 8, wherein the switch includes a triac.

10. An apparatus as claimed in claim 7, wherein the voltage filter includes a zero-cross detection circuit.

11. An apparatus as claimed in claim 10, wherein the current filter includes a zero-cross detection circuit.

12. An apparatus as claimed in claim 11, wherein the controller is operable to produce the control signal when a phase difference between the first and second two-state output signals meets or exceeds a predetermined threshold.

13. An apparatus as claimed in claim 12, wherein the controller is operable to deliver the control signal to the switch after a predetermined amount of time has elapsed.

14. An apparatus as claimed in claim 12, wherein the controller is operable to produce a second control signal.

15. An apparatus as claimed in claim 14, wherein said switch is operable to close in response to said second control signal.

16. An apparatus as claimed in claim 14, wherein the controller is programmed to produce the second control signal a predetermined amount of time after producing the control signal.

17. An apparatus as claimed in claim 16, wherein the controller is a programmable device.

18. A pump comprising:

a housing;

a motor positioned within the housing;

a control module positioned within the housing, the control module including

a voltage filter capable of being coupled to an AC power source and of generating a first two-state output signal;

a current filter capable of being coupled to an AC power source and of generating a second two-state output signal;

a power supply circuit capable of producing a DC power signal;

a programmable device coupled to the voltage filter, the current filter, and the power supply circuit and programmed to produce a control signal based on the time differential between the first and second two-state output signals; and

a switch coupled to the programmable device, operable to open in response to the control signal, and having a semiconductor device coupled in parallel to a second switching device.

19. An apparatus as claimed in claim 18, wherein the semi-conductor device is a triac.

20. An apparatus as claimed in claim 18, wherein the second switching device is a relay.

21. An apparatus as claimed in claim 20, wherein the voltage filter includes a zero-cross detection circuit.

22. An apparatus as claimed in claim 21, wherein the current filter includes a zero-cross detection circuit.

23. An apparatus as claimed in claim 22, wherein the programmable device is programmed to produce the control signal when a phase difference between the first and second two-state output signals meets or exceeds a predetermined threshold.

24. An apparatus as claimed in claim 18, wherein the programmable device is programmed to deliver the control signal to the switch after a predetermined amount of time has elapsed.

25. An apparatus as claimed in claim 18, wherein the programmable device is operable to produce a second control signal.

26. An apparatus as claimed in claim 25, wherein said switch is operable to close in response to said second control signal.

27. An apparatus as claimed in claim 25, wherein the programmable device is programmed to produce the second control signal a predetermined amount of time after producing the control signal.

28. An apparatus as claimed in claim 18, wherein the programmable device is a microcontroller.

29. A method of controlling an electric motor pump coupled to a switch, the method comprising:

providing an AC power signal having a positive half cycle and a negative half cycle;

measuring the voltage of the AC power signal and generating a first two-state output signal that is in a logic high state when the measured voltage is on the positive half cycle and is in a logic low state when the measured voltage is on the negative half cycle;

measuring the current of the AC power signal and generating a second two-state output signal that is in a logic high state when the measured current is on the positive half cycle and is in a logic low state when the measured current is on the negative half cycle;

determining a phase difference based on a time difference between the first two-state output signal and the second two-state output signal;

comparing the phase difference to a predetermined threshold value;

opening the switch if the determined phase difference is equal to or greater than the predetermined threshold value;

closing the switch after a predetermined amount of time has elapsed; and

repeating the acts of measuring the voltage, measuring the current, determining a time difference, comparing the determined phase difference, and opening a switch.

30. A pump control apparatus comprising:

a voltage filter having a zero-cross detection circuit and capable of being coupled to an AC power source and of generating a first two-state output signal;

a current filter having a zero-cross detection circuit and capable of being coupled to an AC power source and of generating a second two-state output signal;

a power supply circuit capable of producing a DC power signal;

a controller coupled to the voltage filter, the current filter, and the power supply circuit and operable to produce a control signal based on the time differential between the first and second two-state output signals; and

a switch having an semiconductor device and a relay coupled in parallel circuit branches, the switch coupled to the controller and operable to open in response to the control signal.

31. An apparatus as claimed in claim 30, wherein the controller is operable to produce the control signal when a phase difference between the first and second two-state output signals meets or exceeds a predetermined threshold.

32. An apparatus as claimed in claim 31, wherein the controller is operable to deliver the control signal to the switch after a predetermined amount of time has elapsed.

33. An apparatus as claimed in claim 31, wherein the controller is operable to produce a second control signal.

34. An apparatus as claimed in claim 33, wherein said switch is operable to close in response to said second control signal.

35. An apparatus as claimed in claim 33, wherein the controller is programmed to produce the second control signal a predetermined amount of time after producing the control signal.

36. An apparatus as claimed in claim 33, wherein the controller is a programmable device.

37. A pump comprising:

a housing;

a motor positioned within the housing;

a control module positioned within the housing, the control module including

a voltage filter capable of being coupled to an AC power source and of generating a first two-state output signal;

a current filter capable of being coupled to an AC power source and of generating a second two-state output signal;

a power supply circuit capable of producing a DC power signal;

a programmable device coupled to the voltage filter, the current filter, and the power supply circuit and programmed to produce a control signal based on the time differential between the first and second two-state output signals; and

a switch having a low heat generating device and a high heat generating device coupled in parallel circuit branches, the switch coupled to the programmable device, and operable to open in response to the control signal.