Electrical transmission or interconnection systems – Plural supply circuits or sources – Substitute or emergency source
Patent
1988-10-14
1989-12-26
Shoop, Jr., William M.
Electrical transmission or interconnection systems
Plural supply circuits or sources
Substitute or emergency source
307 64, 307 87, 361 89, 361 91, 361 92, H02J 400
Patent
active
048900028
ABSTRACT:
A circuit breaker for the protection of electrical devices connected thereto provides immediate detection of power failure even if such failure occurs during the times of line voltage axis crossings. This is accomplished by providing and monitoring the amplitude of a synthesized waveform representing a full-wave rectified replica of the line voltage, combined with a 90.degree. phase-shifted full-wave rectified replica of the line voltage waveform. The composite waveform has a peak-to-peak excursion of approximately 20% about a DC average without nulls. The phase-shifted waveform replicas are produced by a phase shift network configured to provide a strong differentiating function, thereby causing the phase-shifted replicas to reflect virtually instantaneously failure of the power line voltage, and in particular failure in the vicinity of an axis crossing, by an immediate change in amplitude. Transient overvoltages and undervoltages are similarly reflected. Suitable comparators are used to detect excursions beyond preset limits to produce a control signal which is used to actuate the circuit breaker to a power-off condition.
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Ip Paul
Perma Power Electronics, Inc.
Shoop Jr. William M.
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