Interrupt-free, unregulated power supply

• US 4,645,940 A
• Filed: 12/13/1985
• Issued: 02/24/1987
• Est. Priority Date: 09/27/1982
• Status: Expired due to Fees

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Wertheim, Max M.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Shik Luen Paul
• Application Number:
  US06/808,725
• Time in Patent Office: 438 Days
• Field of Search: 307/43, 307/44, 307/47, 307/57, 307/58, 307/60, 307/64, 307/65, 307/66, 307/67, 307/68, 307/73, 307/74, 307/75, 307/76, 307/77, 307/78, 307/79, 307/80, 307/84, 307/85, 307/86, 307/87, 290/4 R, 290/4 A, 290/4 B, 290/4 C, 290/4 D, 290/1 R, 322/20, 322/28, 322/32, 322/29
• US Class Current: 307/66
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

A primary and at least one backup alternating voltage source are coupled to a common load to provide interrupt free electric current to the load through a simplified interconnecting network. Phase control of all but one of the sources is accomplished by monitoring the phase difference across choke coils coupling the sources to the load.

Claims

1. An interrupt-free power supply comprising

at least two AC voltage sources of equal frequency, each having a set of output terminals, at least one of the terminals being grounded;

a number of inductors equal to the number of AC voltage sources, each coupling the ungrounded output terminal of a corresponding one of said AC voltage sources to a common load, whereby the power delivered to the common load by each of said AC voltage sources is related to a voltage phase angle across its associated inductor;

a number of feedback circuit means equal to the number of AC voltage sources, each of said feedback circuit means including phase comparator means for sensing the phase difference between the load voltage and the voltage at the ungrounded output terminal of each of said AC voltage sources to provide a phase control feedback signal for controlling the phase of the associated AC voltage source, whereby if the phase of all of said AC voltage sources, with the exception of one of said AC voltage sources, is constrained to zero with respect to that of said load, only said one of said AC voltage sources not so constrained delivers load current in proportion to a sine of the phase angle between the output terminal of said one of said AC voltage sources and said load;

safety backup means comprising a battery-energized static inverter having a set of output terminals, at least one of the terminals being grounded;

additional feedback circuit means including phase comparator means for sensing the phase difference between the load voltage and the voltage at the ungrounded output terminal of said static inverter to provide a phase control feedback signal for controlling the phase of said static inverter, said additional feedback circuit means being connected in common with said number of feedback circuit means; and

an additional inductor coupling the output terminal of said static inverter to said load, whereby upon failure of all said AC voltage sources, said static inverter supplies a reduced load.

2. An interrupt-free power supply as claimed in claim 1, wherein each of said feedback circuit means comprises means generating a source failure signal indicating whether an output voltage amplitude of its AC voltage source is below a predetermined threshold, said means including a voltage comparator having one input responsive to a signal proportional to the output voltage amplitude of said AC voltage source and another input responsive to a signal proportional to the predetermined threshold.

3. An uninterruptible power supply, comprising

first, second and third salient-pole, synchronous alternators of equal frequency, each of said alternators having a set of output terminals, one of which is grounded;

first, second and third inductors, each connecting the ungrounded output terminal of a corresponding one of said alternators to a common electrical load;

first, second and third voltage phase comparators, each having inputs connected to either side of an associated one of said inductors, each of said voltage phase comparators outputting a voltage phase signal proportional to a voltage phase angle across its associated inductor;

first, second and third voltage comparator means, responsive to said first, second and third alternators, respectively, each outputting a feedback signal indicating whether an output amplitude of the associated alternator has fallen below a predetermined threshold;

logic means generating a source cutout signal and a source failure signal in response to the outputs of said first and second voltage comparator means, the source cutout signal indicating when the output amplitudes of both said first and second alternators are, respectively, below and above said predetermined threshold, said source failure signal indicating when the output amplitudes of both of said first and second alternators are below said predetermined threshold;

first, second and third coupling means coupling, respectively, said first, second and third alternators to prime movers, each of said coupling means being responsive to the like-numbered feedback signal such that a shaft speed of the associated alternator is adjusted in a transient manner until the like-numbered feedback signal reverts to a level associated with the desired voltage phase angle;

static inverter means having a set of output terminals, one of which is grounded;

an additional inductor; and

an additional voltage phase comparator having an input connected to either side of said additional inductor, said additional voltage phase comparator outputting a voltage phase signal proportional to a voltage phase angle across said additional inductor and proportional to the voltage at the ungrounded output terminal of said inverter for controlling the phase of said inverter, said additional voltage phase comparator being connected in common with said first, second and third voltage phase comparators, the output ungrounded terminal of said inverter being coupled to said load via said additional inductor, whereby upon failure of all said alternators, said inverter supplies said reduced load.

4. An uninterruptible power supply, comprising

n salient-pole, synchronous alternators of equal frequency, wherein n is a whole integer equal to at least two, each of said alternators having a set of output terminals, one of which is grounded;

n inductors, each connecting the ungrounded output terminal of a corresponding one of said alternators to a common electrical load;

n voltage phase comparators, each having inputs connected to either side of an associated one of said inductors, each of said voltage phase comparators outputting a voltage phase signal proportional to a voltage phase angle across its associated inductor, each of said n voltage comparator means, responsive to said n alternators, respectively, each outputting a feedback signal indicating whether an output amplitude of the associated alternator has fallen below a predetermined threshold;

logic means generating a source cutout signal and a source failure signal in response to the outputs of said first and second voltage phase comparators, said source cutout signal indicating when the output amplitudes of said first and second alternators are, respectively, below and above said predetermined threshold, said source failure signal indicating when the output amplitudes of both said first and second alternators are below said predetermined threshold;

n coupling means coupling, respectively, said alternators to prime movers, each of said coupling means being responsive to the like-numbered feedback signal such that a shaft speed of the associated alternator is adjusted in a transient manner until the like-numbered feedback signal reverts to a level associated with the desired voltage phase angle;

a static inverter having a set of output terminals, one of which is grounded;

an additional inductor; and

an additional voltage phase comparator having an input connected to either side of said additional inductor, said additional voltage phase comparator outputting a voltage phase signal proportional to a voltage phase angle across said additional inductor and proportional to the voltage at the ungrounded output terminal of said inverter for controlling the phase of said inverter, said additional voltage phase comparator being connected in common with said n voltage phase comparators, the ungrounded output terminal of said inverter being coupled to said load via said additional inductor, whereby upon failure of all said alternators, said inverter supplies the reduced load.