Patent EP0421516A2 successfully refreshed from Google Patents.
EP0029249A2
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EP
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Cycloconverter apparatus with controllable end stop firing pulse control means
Assignee: Westinghouse Electric Corp
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Filing: 1980-11-18
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Granted: —
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Expires: 2000-11-18
Abstract
Abstract In a naturally commutated cycloconverter for converting the output of a variable speed generator to a constant output frequency, e.g., 400 Hz, there is provided an end stop control circuit for ensuring commutation of power switching devices that includes timing wave generators for both rectification and inversion end stops. The timing wave generators are phase locked with the generator outputs but are controllable by end stop bias signal derived from a variable system parameter (e.g., load current) that may be independent of the source, to provide prompt protection against any converter malfunctions due to excess load currents. Further provided is an excess current detector employing, for each phase, a pair of high slew rate, high current unipolar output operational amplifiers connected in a voltage follower configuration with a common pull-up resistor and a common load capacitor to develop a peak current signal representing the greater of the positive and ne- rent signal representing the greater of the positive and negative peaks of the alternating phase current.
Inventors
- 👤 Eric John Stacey
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 07:43
CPC Classifications
H; H02; H02M; H02M5/00; H02M5/02; H02M5/04; H02M5/22; H02M5/25; H02M5/27; H02M5/272
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
105 words
Cycloconverter apparatus comprising: a naturally commutated power circuit for connection between a voltage source of varying frequency and a load to be supplied a.c. power at a constant frequency, said power circuit of the type using a plurality of thyristor type power switches, the apparatus comprising: means for generating a reference voltage at said constant frequency; means for controlling the sequential application of firing pulses to said power switches in accordance with said reference voltage; end stop firing pulse control means for constraining the occurrence of a firing pulse to a given power switch selectively in accordance with load current, source voltage and source frequency.
Claim 2
Dependent Claim
105 words
Cycloconverter apparatus comprising: a naturally commutated power circuit for connection between a voltage source of varying frequency and a load to be supplied a.c. power at a constant frequency, said power circuit of the type using a plurality of thyristor type power switches, the apparatus comprising: means for generating a reference voltage at said constant frequency; means for controlling the sequential application of firing pulses to said power switches in accordance with said reference voltage; end stop firing pulse control means for constraining the occurrence of a firing pulse to a given power switch selectively in accordance with load current, source voltage and source frequency.
Claim 3
Dependent Claim
108 words
Cycloconverter apparatus in accordance with claim 1 wherein: said end stop firing pulse control means comprises a timing waveform generator for each line to neutral source voltage; said timing waveform generator comprising means for producing a series of signals that are phase-locked with the source voltage with a displacement directly related to an excess load current signal, logic circuit means for processing signals received from said means for controlling firing pulses and said timing waveform generator to produce an end stop control signal to constrain the period during which the means for controlling firing pulses upon occurrence of of an excess load current signal of a predetermined magnitude.
Claim 4
Dependent Claim
55 words
Cycloconverter apparatus in accordance with claim 2 wherein: said excess load current signal is developed by means including current sensing means for sensing load current, means for comparing the sensed load current with a D.C. reference signal and means for developing a differential excess current signal and applying said differential signal to said timing generator.
Claim 5
Dependent Claim
31 words
Cycloconverter apparatus in accordance with claim 3 wherein: said end stop firing pulse control means is arranged to constrain the latest occurrence of a firing pulse to a given power switch.
Claim 6
Dependent Claim
55 words
Cycloconverter apparatus in accordance with claim 4 wherein: said end stop firing pulse control means is arranged to constrain both the earliest and latest occurrence of a firing pulse to a given power switch and includes one of said timing waveform generators and logic circuit means for each of the rectification and inversion end stops.
Claim 7
Dependent Claim
78 words
Cycloconverter apparatus in accordance with claim 1 wherein: said means for controlling firing pulses comprises an integral control means wherein multiphase cycloconverter output waveforms are at least partially integrated with respect to a reference waveform to develop sequential firing pulses to said power circuit and said end stop control means overrides said integral control means by inhibiting or forcing occurrence of a firing pulse substantially instantaneously upon the occurrence of a load current that exceeds a predetermined magnitude.
Claim 8
Dependent Claim
120 words
Cycloconverter apparatus as in claim 1 further including: means for generating digital timing waveforms phase locked with applied phase voltage waveforms of a voltage source during normal converter operation and shifted in timing upon application of a control signal; logic circuit means for processing said digital timing waveforms with digital shift register outputs of an integral type firing pulse control circuit to produce inhibiting or forcing end stop firing pulses to said power switches in response to a shift in said timing waveforms; and means for sensing a variable system parameter that is independent of the voltage source and producing a control signal applied to said means for generating timing waveforms when said variable system parameter is outside predetermined limits.
Claim 9
Dependent Claim
80 words
Cycloconverter apparatus in accordance with claim 7 wherein: said means for sensing a variable system parameter and producing a control signal comprises: means for sensing load current; means for responding to peaks of the positive and negative half cycles of said load current and producing a peak current signal in accordance with the maximum of the two; means for comparing said peak current signal with a reference and forming said control signal upon occurrence of of an excess peak current.
Claim 10
Dependent Claim
88 words
Cycloconverter apparatus in accordance with claim 8 wherein: said means for responding to peaks of load current comprises, for each phase of load current, a pair of operational amplifiers connected in a voltage follower configuraiton and arranged to produce a common polarity output current for, respectively, positive and negative polarity load current, a common resistor and common load capacitor connected with the output of said operational amplifiers whereby said capacitor remains, for times long compared to output frequency, at the maximum output level reached due to said peaks.
References Cited (Backward Citations)
No citation records indexed.
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