Uninterruptible power supply systems, voltage regulators and operating methods employing controlled ferroresonant transformer circuits

• US 6,348,782 B1
• Filed: 10/02/1998
• Issued: 02/19/2002
• Est. Priority Date: 10/02/1998
• Status: Expired due to Term

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Powerware Corporation (Eaton Corporation PLC.)
• Inventors: Earle, John Kyle, Oughton, George W. Jr.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Laxton, Gary L.
• Application Number:
  US09/165,859
• Time in Patent Office: 1,236 Days
• Field of Search: 363/75, 323/305, 323/306, 323/310, 323/248, 323/249, 323/254, 323/299, 323/301, 323/302, 307/43, 307/45, 307/46, 307/50, 307/51, 307/52, 307/64, 307/66
• US Class Current: 323/284
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02J 9/067 using multi-primary transformers, e.g. transformer having one primary for each AC energy source and a secondary for the loads

Abstract

An uninterruptable power supply system for producing an AC voltage from at least one of a DC power source or an AC power source includes an input terminal configured to receive an AC voltage from an AC power source, and an inverter operative to produce an AC voltage at an output thereof from a DC power source. A ferroresonant transformer circuit includes a transformer having an input winding, a output winding, and a third winding that forms part of a resonant circuit that produces saturation in the output winding when an AC voltage on the input winding exceeds a predetermined amplitude. A transformer input control circuit is coupled to the input terminal and to the inverter output and is operative to couple at least one of the input terminal and the inverter output to the input winding. The transformer input control circuit variably couples the input terminal to the input winding responsive to at least one of a voltage at the input terminal, a current in the output winding, a voltage on the output winding and a current at the input terminal. Related voltage regulators and methods are also described.

Claims

1. An uninterruptible power supply system for producing an AC voltage from at least one of a DC power source and an AC power source, the system comprising:

an input terminal configured to receive an AC voltage from an AC power source;

an inverter operative to produce an AC voltage at an output thereof from a DC power source;

a ferroresonant transformer circuit including a transformer having an input winding, an output winding, and a third winding that forms part of a resonant circuit that produces saturation in said output winding when an AC voltage on the input winding exceeds a predetermined amplitude; and

a transformer input control circuit coupled to said input terminal and to said inverter output and operative to couple said input terminal and/or said inverter output to said input winding, said transformer input control circuit operative to regulate a circulating current in said resonant circuit by variably coupling said input terminal to said input winding responsive to a control input.

2. A system according to claim 1, wherein said transformer input control circuit is operative to increase a voltage per turn on said input winding responsive to at least one of an increase in a current in said output winding, a decrease in a voltage at said input terminal, and a decrease in a voltage on said output winding and to decrease a voltage per turn on said input winding responsive to at least one of a decrease in a current in said output winding, an increase in a voltage at said input terminal, and an increase in a voltage on said output winding.

3. A system according to claim 2, wherein said transformer input control circuit is operative to increase a voltage per turn on said input winding responsive to a current in said output winding increasing above a first predetermined threshold and to decrease a voltage per turn on said input winding responsive to a current in said output winding falling below a second predetermined threshold.

4. A system according to claim 2, wherein said transformer input control circuit is operative to decrease a voltage per turn on said input winding responsive to a voltage at said input terminal increasing above a first predetermined threshold and to increase a voltage per turn on said input winding responsive to a voltage at said input terminal falling below a second predetermined threshold.

5. A system according to claim 2, wherein said transformer input control circuit is operative to decrease a voltage per turn on said input winding responsive to a voltage on said output winding increasing above a first predetermined threshold and to increase a voltage per turn on said input winding responsive to a voltage on said output winding falling below a second predetermined threshold.

6. A system according to claim 1, wherein said transformer input control circuit is operative to connect said input terminal to said input winding at a location along said input winding selected responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding and a current at said input terminal.

7. A system according to claim 6:

wherein said input winding has a plurality of taps; and

wherein said transformer input control circuit is operative to connect said input terminal to a selected one of said plurality of taps responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding, and a current at said input terminal.

8. A system according to claim 7, wherein said transformer input control circuit comprises a switch operative to connect said input terminal to a selected one of said plurality of taps.

9. A system according to claim 1, further comprising a resonance control circuit coupled to said third winding and operative to control a resonance of said resonant circuit to thereby control a saturation characteristic of said output winding.

10. A system according to claim 9, wherein said resonance control circuit comprises means for increasing, and decreasing capacitance in said resonant circuit.

11. A system according to claim 1, wherein said transformer input control circuit is operative to control a voltage per turn on said input winding to optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage in said output winding and a current at said input terminal.

12. A system according to claim 7, wherein said transformer input control circuit and said resonance control circuit are operative to control a voltage per turn on said input winding and a resonance of said resonant circuit, respectively, to optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding, and a current at said input terminal.

13. A system according to claim 1, wherein said transformer input circuit is operative to couple a selected one of an AC power supply connected at said input terminal or said inverter output to said input winding.

14. A system according to claim 1:

wherein said input winding comprises a first input winding and a second input winding;

wherein said transformer input control circuit is operative to variably couple said input terminal to said first input winding responsive to at least one of a voltage at said input terminal and a current in said output winding; and

wherein said inverter output is coupled to said second input winding.

15. A system according to claim 14, wherein said inverter is operative to produce a regulated AC voltage at said inverter output that is maintained within a predetermined voltage range.

16. A system according to claim 1, in combination with a DC power source connected to said inverter.

40. A system according to claim 1, wherein the control input comprises an operating parameter of the system.

41. A system according to claim 1, wherein the control input comprises at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding and a current at said input terminal.

17. A voltage regulator, comprising:

an input terminal configured to receive an input AC voltage;

a ferroresonant transformer circuit including a transformer having an input winding, an output winding and a third winding, that forms part of a resonant circuit that produces saturation in said output winding when an AC voltage on said input winding exceeds a predetermined amplitude; and

a transformer input control circuit coupled to said input terminal and operative to regulate a circulating current in said resonant circuit by variably coupling said input terminal to said input winding responsive to a control input.

18. A voltage regulator according to claim 17, wherein said transformer input control circuit is operative to variably couple said input terminal to said input winding responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding, and a current at said input terminal.

19. A voltage regulator according to claim 18, wherein said transformer input control circuit is operative to increase a voltage per turn on said input winding responsive to at least one of an increase in a current in said output winding, a decrease in a voltage at said input terminal, and a decrease in a voltage on said output winding, and to decrease a voltage per turn on said input winding responsive to at least one of a decrease in a current in said output winding, an increase in a voltage at said input terminal, and an increase in a voltage on said output winding.

20. A voltage regulator according to claim 19, wherein said transformer input control circuit is operative to increase a voltage per turn on said input winding responsive to a current in said output winding increasing above a first predetermined threshold and to decrease a voltage per turn on said input winding responsive to a current in said output winding falling below a second predetermined threshold.

21. A voltage regulator according to claim 19, wherein said transformer input control circuit is operative to decrease a voltage per turn on said input winding responsive to a voltage at said input terminal increasing above a first predetermined threshold and to increase a voltage per turn on said input winding responsive to a voltage at said input terminal falling below a second predetermined threshold.

22. A voltage regulator according to claim 19, wherein said transformer input control circuit is operative to decrease a voltage per turn on said input winding responsive to a voltage on said output winding increasing above a first predetermined threshold and to increase a voltage per turn on said input winding responsive to a voltage on said output winding falling below a second predetermined threshold.

23. A voltage regulator according to claim 18, wherein said transformer input control circuit is operative to connect said input terminal to said input winding at a location along said input winding selected responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding, and a current at said input terminal.

24. A voltage regulator according to claim 23:

wherein said input winding has a plurality of taps; and

wherein said transformer input control circuit is operative to connect said input terminal to a selected one of said plurality of taps responsive to at least one of a voltage at said input terminal, a current in said input winding, a voltage on said output winding, and a current at said input terminal.

25. A voltage regulator according to claim 24, wherein said transformer control circuit comprises a switch operative to connect said input terminal to a selected one of said plurality of taps.

26. A voltage regulator according to claim 18, further comprising a resonance control circuit coupled to said third winding and operative control a resonance of said resonant circuit to thereby control a saturation characteristic of said output winding.

27. A voltage regulator according to claim 26, wherein said resonance control circuit comprises means for increasing and decreasing capacitance in said resonant circuit.

28. A voltage regulator according to claim 18, wherein said transformer input control circuit is operative to control a voltage per turn on said input winding to optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding and a current at said input terminal.

29. A voltage regulator according to claim 26, wherein said transformer input control circuit and said resonance control circuit are operative to control a voltage per turn on said input winding and a resonance of said resonant circuit to optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation of said voltage regulator responsive to at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding, and a current at said input terminal.

42. A voltage regulator according to claim 17, wherein the control input comprises an operating parameter of the voltage regulator.

30. A method of operating a ferroresonant transformer circuit including a transformer having an input winding, an output winding and a third winding that forms part of a resonant circuit that produces saturation in the output winding when an AC voltage on the input winding exceeds a predetermined amplitude, the method comprising the step of:

variably coupling an AC voltage source to the input winding responsive to a control input to thereby regulate a circulating current in the resonant circuit.

31. A method according to claim 30, wherein said step of variably coupling comprises the step of variably coupling an AC voltage to the input winding responsive to at least one of a voltage at the AC voltage source, a current in the output winding, a voltage on the output winding, and a current at the AC voltage source.

32. A method according to claim 31, wherein said step to variably coupling comprises the step of connecting an input terminal connected to the AC voltage source to the input winding at a selected location along the input winding.

33. A method according to claim 32, wherein the input winding has a plurality of taps, and wherein said step of connecting comprises the step of connecting the input terminal to a selected one of the plurality of taps.

34. A method according to claim 33, wherein said step of connecting comprises the steps of:

connecting the input terminal to a tap that increases a voltage per turn on the input winding, in response to a current in the output winding exceeding a first predetermined threshold; and

connecting the input terminal to a tap that decreases a voltage per turn on the input winding, in response to a current in the output winding falling below a second predetermined threshold.

35. A method according to claim 33, wherein said step of connecting comprises the steps of:

connecting the input terminal to a tap that decreases the number of turns of the input winding across which an AC voltage received at the input terminal is applied, in response to a decrease in an AC voltage received at the input terminal; and

connecting the input terminal to a tap that increases the number of turns of the input winding across which an AC voltage received at the input terminal is applied, in response to an increase in an AC voltage received at the input terminal.

36. A method according to claim 33, wherein said step of connecting comprises the steps of:

connecting the input terminal to a tap that decreases the number of turns of the input winding across which an AC voltage received at the input terminal is applied, in response to a decrease in a voltage on the output winding; and

connecting the input terminal to a tap that increases the number of turns of the input winding across which an AC voltage received at the input terminal is applied, in response to an increase in a voltage on the output winding.

37. A method according to claim 32, further comprising the step of varying a resonance of the resonant circuit to thereby control a saturation characteristic of the output winding.

38. A method according to claim 32, comprising the step of variably coupling the input terminal to the input winding to thereby optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation.

39. A method according to claim 37, comprising the step of variably coupling the input terminal to the input winding and controlling resonance in the resonant circuit to thereby optimize at least one of a surge suppression characteristic, a short circuit current, an efficiency, a line regulation and a load regulation.

43. An uninterruptible power supply system comprising:

an input terminal configured to receive an AC voltage from an AC power source;

an AC voltage generating circuit configured to receive a DC voltage from a DC power source and operative to produce an AC voltage therefrom;

a ferroresonant transformer circuit including a transformer having an input winding and output winding; and

a transformer input control circuit coupled to said input terminal and to the AC voltage generating circuit and operative to couple said input terminal and/or said AC voltage generating circuit to said input winding, said transformer input control circuit operative to variably couple said input terminal to said input winding responsive to a control input.

44. A system according to claim 43, wherein the control input comprises an operating parameter of the system.

45. A system according to claim 43, wherein the control input comprises at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding and a current at said input terminal.

46. A system according to claim 43, wherein the transformer input control circuit is operative to connect said input terminal to said input winding at a location along said input winding that is selected responsive to the control input.

47. A system according to claim 43, wherein the input winding comprises a plurality of taps, and wherein the transformer input control circuit is operative to connect the input terminal to a selected one of the plurality of taps responsive to the control input.

48. A system according to claim 43, wherein the ferroresonant transformer circuit comprises a resonant circuit magnetically coupled to the input winding and the output winding, and wherein the transformer input control circuit is operative to regulate a circulating current in the resonant circuit responsive to the control input.

49. A system according to claim 48, further comprising a resonance control circuit operative to control a resonance of the resonant circuit.

50. A system according to claim 49, wherein the resonance control circuit is operative to increase and decrease a capacitance in the resonant circuit.

51. A system according to claim 50, wherein the resonance control circuit comprises:

a capacitor; and

a control circuit operative to couple and decouple the capacitor to and from the resonant circuit.

52. A system according to claim 43, wherein the AC voltage generating circuit comprises an inverter.

53. A voltage regulator, comprising:

an input terminal configured to receive an input AC voltage;

a ferroresonant transformer circuit including a transformer having an input winding and an output winding; and

a transformer input control circuit coupled to said input terminal and operative to variably couple said input terminal to said input winding responsive to a control input.

54. A voltage regulator according to claim 53, wherein the control input comprises an operating parameter of the system.

55. A voltage regulator according to claim 53, wherein the control input comprises at least one of a voltage at said input terminal, a current in said output winding, a voltage on said output winding and a current at said input terminal.

56. A voltage regulator according to claim 53, wherein the transformer input control circuit is operative to connect said input terminal to said input winding at a location along said input winding that is selected responsive to the control input.

57. A voltage regulator according to claim 56, wherein the input winding comprises a plurality of taps, and wherein the transformer input control circuit is operative to connect the input terminal to a selected one of the plurality of taps responsive to the control input.

58. A voltage regulator according to claim 53, wherein the ferroresonant transformer circuit comprises a resonant circuit magnetically coupled to the input winding and the output winding, and wherein the transformer input control circuit is operative to regulate a circulating current in the resonant circuit responsive to the control input.

59. A voltage regulator according to claim 58, further comprising a resonance control circuit operative to control a resonance of the resonant circuit.

60. A voltage regulator according to claim 59, wherein the resonance control circuit is operative to increase and decrease a capacitance in the resonant circuit.

61. A voltage regulator according to claim 60, wherein the resonance control circuit comprises:

a capacitor; and

a control circuit operative to couple and decouple the capacitor to and from the resonant circuit.