| 摘要 |
<p>PURPOSE:To detect a current on the AC side and thereby to obtain a current equivalent to the current of the DC side by providing an electric valve and an arithmetic and memory ciruit operating when thyristors are turned ON on the occasion when a direct current is supplied to a loady by a mixed bridge containing the thyristors. CONSTITUTION:An alternating current is converted into a direct current by a bridge consisting of diodes 4 and 5 and the thyristors 2 and 3 and the direct current thus obtained is supplied to the load 6 of the field coil or the like. Meanwhile, the current on the AC side is detected by a current transformer 13, the output thereof and a voltage on the DC side are detected by a photocoupler 22 and connected to the electric valve 24 which is turned ON during a period when the thyristors 2 and 3 are turned ON and to the arithmetic and memory circuit containing an operational amplifier 17, and the output of the circuit is compared with a reference value in a setting unit 9 to control the thyristors 2 and 3. Accordingly, an output proportional to a detected current is obtained in the period when the thrystors 2 and 3 are ON, while the current is memorized in the period when they are OFF, and thereby a current waveform equivalent to the one on the load side can be obtained by detecting the current of the AC side.</p> |
