Variable-speed motor drive controller for a pump-motor assembly

• US 6,264,431 B1
• Filed: 05/17/1999
• Issued: 07/24/2001
• Est. Priority Date: 05/17/1999
• Status: Active Grant

• Current Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Original Assignee: Franklin Electric Company Incorporated (EBW, Inc.)
• Inventors: Triezenberg, David M.
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): FASTOVSKY, LEONID M
• Application Number:
  US09/312,880
• Time in Patent Office: 799 Days
• Field of Search: 604/52, 60/392.81, 137/566, 137/351, 732/90.R, 123/520, 239/153, 222/52, 222/55, 248/424, 264/40.3, 318/482, 361/31, 417/34, 417/36, 417/20, 417/8, 417/45, 417/19, 417/44.2, 417/26
• US Class Current: 417/36
• CPC Class Codes: F04D 13/08 for submerged use
• CPC Class Codes: F04D 15/0066 by changing the speed, e.g. of the driving engine

Abstract

A liquid pump system for providing liquid to a tank includes a variable-speed motor drive and a control circuit coupling the variable-speed motor drive to a power source. The control circuit has a switch that may be disposed in a state according to the amount of liquid in the tank. The control circuit provides for supplying power to the variable-speed motor drive from the power source regardless of the state of the switch. The control circuit may include a transmitter that generates a high frequency signal representative of the state of the switch. In that embodiment, a detector coupled to the variable-speed motor drive receives the high frequency signal to control operation of the liquid pump system.

Claims

1. A pump system for providing liquid to a tank, comprising:

a variable-speed motor drive;

a pair of conductors coupled to the variable-speed motor drive to supply power to the variable-speed motor drive; and

a switch disposed in a state in accordance with an amount of liquid in the tank wherein;

the switch is coupled to at least one conductor of the pair of conductors for control of the variable-speed motor drive; and

power is supplied to the variable-speed motor drive via the pair of conductors regardless of the state of the switch.

2. The pump system of claim 1, further comprising a third conductor coupling the switch to the variable-speed motor drive.

3. The pump system of claim 1, further comprising a bypass circuit connected to at least one of the pair of conductors in parallel with the switch.

4. The pump system of claim 3, wherein:

the bypass circuit includes a rectifying element; and

the pump system further comprises a sensor coupled to the variable-speed motor drive that detects whether the pair of conductors are supplying half-wave rectified power.

5. The pump system of claim 1, wherein the switch comprises a triac gated by a pressure switch in communication with the liquid.

6. The pump system of claim 5, wherein the pressure switch comprises a reed switch responsive to a position of a magnet determined by the pressure of the liquid.

7. The pump system of claim 1, further comprising a transmitter coupled to the switch and the pair of conductors to generate a high frequency signal on the pair of conductors representative of the state of the switch.

8. The pump system of claim 7, further comprising a detector coupled to the pair of conductors and the variable-speed motor drive and responsive to the high frequency signal to control the variable-speed motor drive.

9. The pump system of claim 8, wherein the transmitter comprises an oscillator and the detector comprises a phase-locked loop circuit.

10. The pump system of claim 8, wherein the transmitter and the detector are coupled to the pair of conductors via respective transformers.

11. The pump system of claim 10, further comprising a pair of capacitors connected across the pair of conductors.

12. The pump system of claim 11, wherein:

the transmitter and the detector are coupled to the pair of conductors via a respective transformer; and

each transformer, together with a respective capacitor of the pair of capacitors, couples the pair of conductors together.

13. A pump system powered by a power source to provide liquid to a tank, comprising:

a variable-speed motor drive; and

a control circuit coupled to the power source and the variable-speed motor drive wherein the control circuit comprises;

a switch disposed in a state in accordance with an amount of liquid in the tank; and

a bypass circuit connected in parallel with the switch that allows power to be supplied to the variable-speed motor drive from the power source regardless of the state of the switch.

14. The pump system of claim 13, wherein:

the switch is disposed in a first state during a low liquid condition and a second state during a high liquid condition;

the variable-speed motor drive comprises a rectifier and an inverter;

the rectifier is supplied with power from the power source via the bypass circuit when the switch is disposed in either the first state or the second state; and

the inverter is responsive to the state of the switch to provide three-phase power to a motor coupled to the variable-speed motor drive during the low liquid condition.

15. The pump system of claim 13, further comprising a first power conductor and a second power conductor that couple the variable-speed motor drive to the power source wherein at least one of the first power conductor and the second power conductor is coupled to the switch such that a signal having an electrical property determined by the state of the switch is supplied to the variable-speed motor drive.

16. The pump system of claim 15, wherein the switch comprises:

a pressure switch in communication with the liquid; and

a triac gated by the pressure switch and coupled to the first power conductor.

17. The pump system of claim 13, wherein the bypass circuit comprises a rectifier such that the variable-speed motor drive is supplied with half-wave rectified power when the switch is open.

18. The pump system of claim 17, further comprising a sensor coupled to the control circuit that detects whether the variable-speed motor drive is supplied with half-wave rectified power via the rectifier of the bypass circuit.

19. A pump system for providing liquid to a tank, comprising:

a variable-speed motor drive;

a pair of conductors coupled to the variable-speed motor drive to supply power thereto;

a transmitter inductively coupled to the pair of conductors to generate a high frequency signal representative of an amount of liquid in the tank; and

a detector coupled to the variable-speed motor drive and inductively coupled to the pair of conductors to receive the high frequency signal therefrom.

20. The pump system of claim 19, further comprising means coupled to the transmitter for indicating the amount of liquid in the tank.

21. The pump system of claim 20, wherein the indicating means comprises a pressure switch disposed in a state in accordance with the amount of liquid in the tank.

22. The pump system of claim 19, further comprising a pair of capacitors connected across the pair of conductors.

23. The pump system of claim 22, wherein:

the transmitter and the detector are coupled to the pair of conductors via a respective transformer; and

each transformer, together with a respective capacitor of the pair of capacitors, couples the pair of conductors together.

24. The pump system of claim 19, wherein the transmitter comprises an oscillator.

25. The pump system of claim 24, wherein the transmitter further comprises an amplifier coupled to the oscillator via a switch that is disposed in a closed state when the amount of liquid in the tank reaches a low level.

26. The pump system of claim 19, wherein the detector comprises a phase-locked loop circuit that develops a digital output signal representative of whether the high frequency signal is present on the pair of conductors.

27. The pump system of claim 26, wherein the variable-speed motor drive comprises a microcontroller responsive to the digital output signal.

28. A control circuit for a pump system having a tank for storing liquid and a variable-speed motor drive, the control circuit comprising:

a switch disposed in a state in accordance with an amount of liquid in the tank;

a bypass circuit connected in parallel with the switch such that the variable-speed motor is supplied with power when the switch is disposed in an open state; and

a detector responsive to the power to generate a control signal representative of the state of the switch to control the variable-speed motor drive.

29. The control circuit of claim 28, wherein the switch comprises a pressure switch and a triac gated by the pressure switch.

30. The control circuit of claim 28, wherein the bypass circuit comprises a rectifier such that the power comprises half-wave rectified current.

31. The control circuit of claim 28, wherein the detector comprises an optocoupler.

32. A control circuit for a pump system having a variable-speed motor drive and a tank for storing liquid, the control circuit comprising:

means for indicating an amount of liquid in the tank;

a first power conductor and a second power conductor that supply power to the variable-speed motor drive;

a transmitter coupled to the indicating means and at least one of the first and second power conductors to generate a high frequency signal representative of the amount of liquid in the tank; and

a detector coupled to at least one of the first and second power conductors and to the variable-speed motor drive and responsive to the high frequency signal to control the variable-speed motor drive.

33. The control circuit of claim 32, wherein the indicating means comprises a pressure switch disposed in a state in accordance with the amount of liquid in the tank.

34. The control circuit of claim 32, wherein the transmitter and the detector are inductively coupled to at least one of the first and second power conductors via a first transformer and a second transformer, respectively.

35. The control circuit of claim 34, wherein the first and second transformers are saturated by current that powers the variable-speed motor drive.

36. The control circuit of claim 34, further comprising a first capacitance and a second capacitance wherein each of the first capacitance and the second capacitance couples the first power conductor to the second power conductor.

37. The control circuit of claim 36, wherein:

the first capacitance and the first transformer are connected in series to couple the first power conductor to the second power conductor; and

the second capacitance and the second transformer are connected in series to couple the first power conductor to the second power conductor.

38. The control circuit of claim 32, wherein the transmitter comprises an oscillator.

39. The control circuit of claim 38, wherein the transmitter further comprises an amplifier coupled to the oscillator and responsive to the indicating means.

40. The control circuit of claim 32, wherein the detector comprises a phase-locked loop circuit.

41. A controller for a variable-speed motor drive provided with current from a power source for pumping liquid to a tank, the controller comprising:

a pressure-sensitive device having a diaphragm responsive to an amount of liquid in the tank; and

a current-carrier circuit having a transformer and coupled to the pressure-sensitive device and the variable-speed motor drive to provide to the variable-speed motor drive a signal indicative of the amount of liquid in the tank wherein the current saturates the transformer.

42. The controller of claim 41, wherein the current-carrier circuit comprises an oscillator coupled to the transformer that generates a high frequency signal.

43. The controller of claim 42, wherein the pressure-sensitive device comprises a switch having a state determined by a position of the diaphragm.

44. The controller of claim 43, wherein the current-carrier circuit further comprises an amplifier coupled to the oscillator by the switch.

45. The controller of claim 41, wherein the transformer comprises a ferrite core.