Thyristor converter control apparatus including differentiation arrangement to prevent abnormal operation

Claim 3

A thyristor converter control apparatus as claimed in claim 1, wherein said plural differentiation means include first differentiation means generating output signals indicative of the start point of voltage detection under the condition of the presence of the voltage and second differentiation means generating output signals indicative of the end point of voltage detection under the condition of the presence of the voltage, and said signal synthesis means generate a synthesized signal indicative of the presence of the voltage in response to the appearance of an output signal from any one.of said first differentiation means or indicative of the absence of the voltage in response to the appearance of at least two output signals from said second differentiation means.

Claim 6

A thyristor converter control apparatus as claimed in claim 1, wherein said voltage detectors and said differentiation means are connected to one another through voltage converters for converting electrical signal generated by said voltage detectors indicative of the presence or absence of voltage applied to the thyristors into optical signals and photo-electrical transducers for converting said optical signals into electrical signals.

Claim 7

A thyristor converter control apparatus as claimed in claim 3, wherein said voltage detectors and said first and second differentiation means are connected to one another through voltage converters for converting electrical signals generated by said voltage detectors indicative of the presence or absence of voltage applied to the thyristors into optical signals and photo-electrical transducers for converting said optical signals into electrical signals.

Claim 8

A thyristor converter control apparatus including a plurality of series-connected thyristors comprising: a plurality of voltage detectors for detecting the presence or absence of voltage applied to said thyristors respectively; a plurality of differentiation means for differentiating the output signals from said voltage detectors respectively; signal synthesis means for synthesizing the output signals from said differentiation means and for judging the presence or absence of the voltage applied to said thyristors; and trigger pulse generating means for generating pulses to trigger said thyristors in response to a judgment by the signal synthesis circuit of the presence of the voltage applied to said thyristors, wherein said plural differentiation means includes first differentiation means generating output signals indicative of the start point of voltage detection under the condition of the presence of the voltage and second differentiation means generating output signals indicative of the end point of voltage detection under the condition of the presence of the voltage, and said signal synthesis means generate a synthesized signal indicative of the presence of the voltage in response to the appearance of an output signal from any one of said first differentiation means or indicative of the absence of the voltage in response to the appearance of at least two output signals from said second differentiation means.

Claim 9

A thyristor converter control apparatus including a plurality of series-connected thyristors comprising: a plurality of voltage detectors for detecting the presence or absence of voltage applied to said thyristors respectively; a plurality of differentiation means for differentiating the output signals from said voltage detectors respectively; signal synthesis means for synthesizing the output signals from said differentiation means and for judging the presence or absence of the voltage applied to said thyristors; and trigger pulse generating means for generating pulses to trigger said thyristors in response to a judgment by the signal synthesis circuit of the presence of the voltage applied to said thyristors, wherein said plural differentiation means includes first differentiation means generating output signals indicative of the start point of voltage detection under the condition of the presence of the voltage and second differentiation means generating output signals indicative of the end point of voltage detection under the condition of the presence of the voltage, and said signal synthesis means generate a synthesized signal indicative of the presence of the voltage in response to the appearance of an output signal from any one of said first differentiation means or indicative of the absence of the voltage in response to the appearance of at least two output signals from said second differentiation means.

Claim 12

An apparatus according to claim 7, wherein said means for logically combining outputs of the plurality of first differentiation means comprises a logic OR circuit.

Claim 13

An apparatus according to claim 7, wherein said means for generating a forward voltage detection signal comprises a SET-RESET flip-flop circuit, and wherein the means for logically combining is coupled to said flip-flop circuit to provide a SET signal to the flip-flop circuit when the logical combining means provides an output indicating the presence of a forward voltage being applied to the thyristors based on the combination of outputs of the first differentiation means to generate the first voltage detection signal.

Claim 14

An apparatus according to claim 9, further comprising means for resetting the flip-flop circuit upon determining that forward voltage has ceased to be applied to the thyristors or upon determining that a trigger pulse has been generated for a predetermined time interval.

Claim 15

An apparatus according to claim 10, wherein said means for resetting the flip-flop circuit includes a plurality of second differentiation means coupled to receive output signals of said voltage detectors through a plurality of corresponding converters to provide an indication of an end of the application of forward voltage to said thyristors.