| 摘要 |
PROBLEM TO BE SOLVED: To eliminate a current transformer for the detection of the misignition of a thyristor in a DC filter circuit. SOLUTION: A current applied to a thyristor 11 is detected simultaneously with a current applied to a conventionally provided filter capacitor 5 by a current transformer 17 which detects the current applied to the filter capacitor 5 and supplied to a thyristor operation judging means 22. If the current transformer 17 detects a current whose direction is opposite to the direction of the current normally applied to the filter capacitor 5 and the detected current value is approximately equal to a value which is obtained by dividing the voltage of the filter capacitor 5 which is detected by a voltage detector 16 by the resistance value of a resistor 12 and, further, an off-instruction is given to the thyristor 11, the thyristor operation judging means 22 judges that the misignition of the thyristor 11 exists. With this constitution, by changing wiring patterns 20 and 21 only a little, a current transformer which is required in a conventional constitution for the detection of the thyristor current in addition to the current transformer 17 for the filter capacitor 5 can be eliminated and hence the number of components is reduced. |
