Multi-input power transfer and uninterruptible power supply apparatus and methods of operation thereof

• US 6,330,176 B1
• Filed: 11/15/2000
• Issued: 12/11/2001
• Est. Priority Date: 11/15/2000
• Status: Expired due to Term

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Powerware Corporation (Eaton Corporation PLC.)
• Inventors: Shah, Dinesh, Thrap, Guy C.
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/713,431
• Time in Patent Office: 391 Days
• Field of Search: 363/142, 307/43, 307/64, 307/85, 307/86
• US Class Current: 363/142
• CPC Class Codes: H02J 3/007 Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing uninterruptable power supply H02J9/00
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems

Abstract

A power transfer apparatus includes a first switch operative to couple and decouple a first AC power source to and from an AC power bus responsive to a first control signal and a second switch operative to couple and decouple a second AC power source to and from the AC power bus responsive to a second control signal. A first switch control circuit generates the first control signal responsive to a first AC source voltage produced by the first AC power source and to a first inhibit signal and generates a second inhibit signal responsive to a state of the first switch. A second switch control circuit generates the second control signal responsive to a second AC source voltage produced by the second AC power source and to the second inhibit signal and generates the first inhibit signal responsive to a state of the second switch. In some embodiments, the first control signal may comprise a current in a coil of a relay that couples and decouples the first AC power source to and from the AC power bus responsive to the coil current. A relay driver circuit may control the coil current responsive to the enable signal and the first inhibit signal. A current detector circuit may generate the second inhibit signal responsive to the coil current. Related uninterruptible power supply (UPS) systems and methods are also discussed.

Claims

1. A power transfer apparatus for selectively transferring power to an AC power bus from first and second AC power sources, the apparatus comprising:

a first switch operative to couple and decouple the first AC power source to and from the AC power bus responsive to a first control signal;

a second switch operative to couple and decouple the second AC power source to and from the AC power bus responsive to a second control signal;

a first switch control circuit that generates the first control signal responsive to a first AC source voltage produced by the first AC power source and to a first inhibit signal and that generates a second inhibit signal responsive to a state of the first switch; and

a second switch control circuit that generates the second control signal responsive to a second AC source voltage produced by the second AC power source and to the second inhibit signal and that generates the first inhibit signal responsive to a state of the second switch.

2. An apparatus according to claim 1, wherein the first switch control circuit comprises:

a voltage detector circuit operative to generate an enable signal responsive to the first AC source voltage;

a driver circuit operative to generate the first control signal responsive to the enable signal and the first inhibit signal; and

an inhibit signal generator circuit operative to generate the second inhibit signal responsive to the first control signal.

3. An apparatus according to claim 2:

wherein the first switch comprises a relay including a switching element coupled to the AC power bus and configured to be coupled to the first AC power source and a coil operative to cause the switching element to couple and decouple the AC power source to and from the AC power bus responsive to a current in the coil;

wherein the driver circuit comprises a relay driver circuit that controls the current in the coil responsive to the enable signal and the first inhibit signal; and

wherein the inhibit signal generator circuit comprises a current detector circuit operative to generate the second inhibit signal responsive to the current in the coil.

4. An apparatus according to claim 2, wherein the voltage detector circuit comprises an over/under voltage detector circuit operative to assert the enable signal when the first AC source voltage is within a predetermined voltage window and to deassert the enable signal when the first AC source voltage is outside of the predetermined voltage window.

5. An apparatus according to claim 1:

wherein the first switch control circuit is further operative to cause the first switch to couple the first AC power source to the AC power bus when the first AC source voltage meets a first predetermined criterion and the first inhibit signal is deasserted;

wherein the first switch control circuit is further operative to cause the first switch to decouple the first AC power source from the AC power bus when the first AC source voltage fails to meet the first predetermined criterion; and

wherein the first switch control circuit is further operative to cause the first switch to decouple the first AC power source from the AC power bus when the first inhibit signal is asserted.

6. An apparatus according to claim 5:

wherein the second switch control circuit is further operative to cause the second switch to couple the second AC power source to the AC power bus when the second AC source voltage meets a second predetermined criterion and the second inhibit signal is deasserted;

wherein the second switch control circuit is further operative to cause the second switch to decouple the second AC power source from the AC power bus when the second AC source voltage fails to meet the second predetermined criterion; and

wherein the second switch control circuit is further operative to cause the second switch to decouple the second AC power source from the AC power bus when the second inhibit signal is asserted.

7. An apparatus according to claim 1:

wherein the first switch control circuit is further operative to assert the second inhibit signal when the first switch couples the first AC power source to the AC power bus, to maintain assertion of the second inhibit signal for a first predetermined interval following decoupling of the first AC power source from the AC power bus, and to deassert the second inhibit signal following the first predetermined interval; and

wherein the second switch control circuit is further operative to cause the second switch to decouple the second AC power source from the AC power bus responsive to assertion of the second inhibit signal.

8. An apparatus according to claim 7:

wherein the second switch control circuit is further operative to assert the first inhibit signal when the second switch couples the second AC power source to the AC power bus, to maintain assertion of the first inhibit signal for a second predetermined interval following decoupling of the second AC power source from the AC power bus, and to deassert the first inhibit signal following the second predetermined interval; and

wherein the first switch control circuit is further operative to cause the first switch to decouple the first AC power source from the AC power bus responsive to assertion of the first inhibit signal.

9. An apparatus according to claim 1, wherein the first and second switch control circuits are galvanically isolated from one another.

10. An apparatus according to claim 1, wherein the first and second inhibit signals comprise respective optical signals.

11. An apparatus according to claim 1:

wherein the first switch control circuit is further operative to generate the first control signal responsive to the first AC source voltage, to the first inhibit signal and to a third inhibit signal; and

wherein the second switch control is further operative to generate the second control signal responsive to the second AC source voltage, to the second inhibit signal and to a fourth inhibit signal; and

wherein the apparatus further comprises;

a communications interface circuit configured to receive external signals on an external signal line and operative to generate the third and fourth inhibit signals responsive thereto.

12. An apparatus according to claim 11:

wherein the first switch control circuit is further operative to generate a first status signal that is indicative of a status of the first switch control circuit;

wherein the second switch control circuit is further operative to generate a second status signal that is indicative of a status of the second switch control circuit; and

wherein the communications interface circuit is configured to receive the first and second status signals and operative to transmit signals on the external signal line responsive to the first and second status signals.

13. An apparatus according to claim 12:

wherein the first status signal is indicative of a magnitude of the first AC source voltage; and

wherein the second status signal is indicative of a magnitude of the second AC source voltage.

14. An apparatus according to claim 12, wherein the first switch control circuit, the second switch control circuit and the communications interface circuit are galvanically isolated from one another.

15. An apparatus according to claim 14, wherein the first inhibit signal, the second inhibit signal, the third inhibit signal, the fourth inhibit signal, the first status signal and the second status signals comprise respective optical signals.

16. An uninterruptible power supply (UPS) system, comprising:

an AC power bus;

a first switch operative to couple and decouple a first AC power source to and from the AC power bus responsive to a first control signal;

a second switch operative to couple and decouple a second AC power source to and from the AC power bus responsive to a second control signal;

a first switch control circuit that generates the first control signal responsive to a first AC source voltage produced by the first AC power source and to a first inhibit signal and that generates a second inhibit signal responsive to a state of the first switch;

a second switch control circuit that generates the second control signal responsive to a second AC source voltage produced by the second AC power source and to the second inhibit signal and that generates the first inhibit signal responsive to a state of the second switch; and

a UPS subsystem having a first input coupled to the AC power bus and a second input configured to be coupled to a DC power source, the UPS subsystem operative to generate an AC output voltage from an AC voltage at the first input or from a DC voltage at the second input.

17. A system according to claim 16, wherein the first switch control circuit comprises:

a voltage detector circuit operative to generate an enable signal responsive to the first AC source voltage;

a driver circuit operative to generate the first control signal responsive to the enable signal and the first inhibit signal; and

an inhibit signal generator circuit operative to generate the second inhibit signal responsive to the first control signal.

18. A system according to claim 17:

wherein the first switch comprises a relay including a switching element coupled to the AC power bus and configured to be coupled to the first AC power source and a coil operative to cause the switching element to couple and decouple the AC power source to and from the AC power bus responsive to a current in the coil;

wherein the first control signal comprises the current in the coil;

wherein the driver circuit comprises a relay driver circuit that controls the current in the coil responsive to the enable signal and the first inhibit signal; and

wherein the inhibit signal generator circuit comprises a current detector circuit operative to generate the second inhibit signal responsive to the current in the coil.

19. A system according to claim 17, wherein the voltage detector circuit comprises an over/under voltage detector circuit operative to assert the enable signal when the first AC source voltage is within a predetermined voltage window and to deassert the enable signal when the first AC source voltage is outside of the predetermined voltage window.

20. A system according to claim 16:

wherein the first switch control circuit is further operative to assert the second inhibit signal when the first switch couples the first AC power source to the AC power bus, to maintain assertion of the second inhibit signal for a first predetermined interval following decoupling of the first AC power source from the AC power bus, and to deassert the second inhibit signal following the first predetermined interval; and

wherein the second switch control circuit is further operative to cause the second switch to decouple the second AC power source from the AC power bus responsive to assertion of the second inhibit signal.

21. A system according to claim 20:

wherein the second switch control circuit is further operative to assert the first inhibit signal when the second switch couples the second AC power source to the AC power bus, to maintain assertion of the first inhibit signal for a second predetermined interval following decoupling of the second AC power source from the AC power bus, and to deassert the first inhibit signal following the second predetermined interval; and

wherein the first switch control circuit is further operative to cause the first switch to decouple the first AC power source from the AC power bus responsive to assertion of the first inhibit signal.

22. A system according to claim 21, wherein the UPS subsystem is operative to generate the AC output voltage from a DC voltage at the second input in the first and second predetermined intervals.

23. A system according to claim 16, wherein the first and second switch control circuits are galvanically isolated from one another.

24. A system according to claim 16, wherein the first and second inhibit signals comprise respective optical signals.

25. A system according to claim 16:

wherein the first switch control circuit is further operative to generate the first control signal responsive to the first AC source voltage, to the first inhibit signal and to a third inhibit signal; and

wherein the second switch control is further operative to generate the second control signal responsive to the second AC source voltage, to the second inhibit signal and to a fourth inhibit signal; and

wherein the system further comprises;

a communications interface circuit configured to receive externally-applied signals on an external signal line and operative to generate the third and fourth inhibit signals responsive thereto; and

a controller circuit coupled to the UPS subsystem and to the external signal line and operative to generate the externally applied signals.

26. A system according to claim 25, wherein the controller circuit is operative to generate signals on the external signal line that cause the first and second control circuits to decouple the first and second AC power sources from the AC power bus and to cause the UPS subsystem to concurrently generate the AC output voltage from the DC power source.

27. A system according to claim 25:

wherein the first switch control circuit is further operative to generate a first status signal that is indicative of a status of the first switch control circuit;

wherein the second switch control circuit is further operative to generate a second status signal that is indicative of a status of the second switch control circuit;

wherein the communications interface circuit is configured to receive the first and second status signals and operative to transmit signals on the external signal line responsive to the first and second status signals; and

wherein the controller circuit is operative to receive the transmitted signals.

28. A system according to claim 27, wherein the controller circuit is operative, responsive to the first and second status signals, to cause the UPS subsystem to generate the AC output voltage from the DC voltage at the second input when the first and second AC source voltages are unacceptable.

29. A system according to claim 27:

wherein the first status signal is indicative of a magnitude of the first AC source voltage; and

wherein the second status signal is indicative of a magnitude of the second AC source voltage.

30. A system according to claim 27, wherein the first switch control circuit, the second switch control circuit and the communications interface circuit are galvanically isolated from one another.

31. A system according to claim 27, wherein the first inhibit signal, the second inhibit signal, the third inhibit signal, the fourth inhibit signal, the first status signal and the second status signals comprise respective optical signals.

32. A method of selectively transferring power to an AC power bus from first and second AC power sources, the method comprising:

providing first and second switches that are operative to couple and decouple the first and second AC power sources to and from the AC power bus responsive to first and second control signals;

generating the first control signal responsive to a first AC source voltage produced by the first AC power source and to a first inhibit signal;

generating the second control signal responsive to a second AC source voltage produced by the second AC power source and to a second inhibit signal;

generating the first inhibit signal responsive to a state of the second switch; and

generating the second inhibit signal responsive to a state of the first switch.

33. A method according to claim 32, further comprising selectively generating an AC voltage from an AC voltage on the AC power bus or from a DC voltage produced by a DC power source.

34. A method according to claim 32, wherein generating the second inhibit signal comprises generating the second inhibit signal responsive to the first control signal.

35. A method according to claim 32, wherein generating the first control signal comprises:

generating an enable signal responsive to the first AC source voltage; and

generating the first control signal responsive to the enable signal and to the first inhibit signal.

36. A method according to claim 35:

wherein the first switch comprises a relay including a switching element coupled to the AC power bus and configured to be coupled to the first AC power source and a coil operative to cause the switching element to couple and decouple the AC power source to and from the AC power bus responsive to a current in the coil; and

wherein generating the first control signal responsive to the enable signal and to the first inhibit signal comprises controlling a current in the coil responsive to the enable signal and to the first inhibit signal.

37. A method according to claim 36:

wherein generating the second inhibit signal comprises generating the second inhibit signal responsive to the current in the coil.

38. A method according to claim 35, wherein generating the enable signal comprises:

asserting the enable signal when the first AC source voltage is within a predetermined voltage window; and

deasserting the enable signal when the first AC source voltage is outside the predetermined voltage window.

39. A method according to claim 32, wherein generating the first control signal comprises:

generating the first control signal such that the first switch couples the first AC power source to the AC power bus when the first AC source voltage meets a first predetermined criterion and the first inhibit signal is deasserted;

generating the first control signal such that the first switch decouples the first AC power source from the AC power bus when the first AC source voltage fails to meet the first predetermined criterion; and

generating the first control signal such that the first switch decouples the first AC power source from the AC power bus when the first inhibit signal is asserted.

40. A method according to claim 32:

wherein generating the second inhibit signal comprises;

asserting the second inhibit signal when the first switch couples the first AC power source to the AC power bus;

continuing assertion of the second inhibit signal for a predetermined interval following decoupling of the first AC power source from the AC power bus; and

deasserting the second inhibit signal following the predetermined interval; and

wherein generating the second control signal comprises generating the second control signal such that the second switch decouples the second AC power source from the AC power bus responsive to assertion of the second inhibit signal.

41. A method according to claim 40, wherein a UPS is coupled to the AC power bus, and wherein the method further comprises operating the UPS such that it generates an AC output voltage from a DC power source in the predetermined interval.

42. A method according to claim 32, wherein the first and second inhibit signals comprise respective optical signals.

43. A method according to claim 32:

wherein generating the first control signal comprises generating the first control signal responsive to the first AC source voltage, to the first inhibit signal and to a third inhibit signal;

wherein generating the second control signal comprises generating the second control signal responsive to the second AC source voltage, to the second inhibit signal and to a fourth inhibit signal; and

wherein the method further comprises;

receiving external signals at a communications interface circuit; and

generating the third and fourth inhibit signals responsive to the received external signals.

44. A method according to claim 43, further comprising:

generating a first status signal that is indicative of a status of the first switch control circuit;

generating a second status signal that is indicative of a status of the second switch control circuit;

receiving the first and second status signals at the communications interface circuit; and

transmitting signals from the communications interface circuit responsive to the first and second status signals.

45. A method according to claim 44:

wherein the first status signal is indicative of a magnitude of the first AC source voltage; and

wherein the second status signal is indicative of a magnitude of the second AC source voltage.