Relay switching apparatus
First Claim
1. A switching circuit for selectively coupling a load to an A.C. power source, said switching circuit comprising:
- (a) a master relay including a master relay contact and a master relay coil;
(b) a pilot relay including a pilot relay and a pilot relay coil, said master and pilot relay contacts being coupled in series with each other and being coupled between said load and said power source to cause said power source to be coupled to said load whenever both said master and pilot relay contacts are closed; and
to cause said power source to be completely disconnected from said load whenever at least said pilot relay contact is open;
said pilot relay contact being devoid of any additional conductive element thereacross;
(c) a single commutating diode coupled in parallel only with said master relay contact; and
(d) timing and control circuit means for performing a switching operation in which;
(1) said master relay contact is opened during a first half-cycle of the A.C. waveform of said power source during which said single commutating diode is forward-biased;
(2) the state of said pilot relay contact is changed during a second half-cycle of said A.C. waveform, said second half-cycle being that half-cycle of said A.C. waveform immediately following said first half-cycle, and during which said single commutating diode is reverse-biased.(3) said master relay contact is closed during a third half-cycle of said A.C. waveform, said third half-cycle being that half-cycle of said A.C. waveform immediately following said second half-cycle.
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Accused Products
Abstract
A switching circuit for selectively coupling a load to an A.C. power source is disclosed. The switching circuit includes a diode-commutated master relay contact and a pilot relay contact coupled in series therewith. The master and pilot relay contacts are coupled between a load and the power source in such a manner that power is applied to the load whenever both the master and pilot relay contacts are closed. A timing and control circuit performs a switching operation to open the master relay contact during a first half-cycle of the A.C. waveform of the power source during which the commutating diode is forward-biased. The pilot relay contact changes state during the next half-cycle of the A.C. waveform and the master relay contact is reclosed during the following half-cycle of the A.C. waveform.
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Citations
17 Claims
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1. A switching circuit for selectively coupling a load to an A.C. power source, said switching circuit comprising:
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(a) a master relay including a master relay contact and a master relay coil; (b) a pilot relay including a pilot relay and a pilot relay coil, said master and pilot relay contacts being coupled in series with each other and being coupled between said load and said power source to cause said power source to be coupled to said load whenever both said master and pilot relay contacts are closed; and
to cause said power source to be completely disconnected from said load whenever at least said pilot relay contact is open;
said pilot relay contact being devoid of any additional conductive element thereacross;(c) a single commutating diode coupled in parallel only with said master relay contact; and (d) timing and control circuit means for performing a switching operation in which; (1) said master relay contact is opened during a first half-cycle of the A.C. waveform of said power source during which said single commutating diode is forward-biased; (2) the state of said pilot relay contact is changed during a second half-cycle of said A.C. waveform, said second half-cycle being that half-cycle of said A.C. waveform immediately following said first half-cycle, and during which said single commutating diode is reverse-biased. (3) said master relay contact is closed during a third half-cycle of said A.C. waveform, said third half-cycle being that half-cycle of said A.C. waveform immediately following said second half-cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A switching circuit for selectively coupling any combination of a plurality N of loads, where N is an integer greater than 1, to an A.C. power source, said switching circuit comprising:
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(a) a master relay including a master relay contact and a master relay coil; (b) a plurality N of pilot relays, each of said pilot relays including a pilot relay contact and a pilot relay coil, each of said pilot relay contacts being coupled in series with a respective one of said N loads;
said master relay contact being coupled in series with all of said pilot relay contacts to said power source insuch manner that each individual one of said N loads is connected to said power source only when both said master relay and the pilot relay contact associated with that individual one of said N loads are closed;(c) a single commutating diode coupled in parallel only with said master relay contact;
each of said pilot relay contacts being devoid of any additional conductive element thereacross;(d) timing and control circuit means for performing a switching operation in which; (1) said master relay contact is opened during a first half-cycle of the A.C. waveform of said power source during which said single commutating diode is forward-biased; (2) the state of at least one of said pilot relay contacts is changed during a second half-cycle of said A.C. waveform, said second half-cycle being that half-cycle of said A.C. waveform immediately following said first half-cycle, during which second half-cycle said single commutating diode is reverse-biased; and (3) said master relay contact is closed during a third half-cycle of said A.C. waveform, said third half-cycle being that half-cycle of said A.C. waveform immediately following said second half-cycle. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification