| 摘要 |
PURPOSE:To make a demagnetization current always constant by making the demagnetization current flow in a definite direction by detection means and by sending a detection signal when a required set value is obtained. CONSTITUTION:After an excitation operation is finished, thyristors 13, 15 are operated, a demagnetization current flows in the direction shown by a broken line arrow and a demagnetization magnetic field is generated from electromag netic coils 6, 7. A meter relay 20 detects the demagnetization current when the current of a predetermined direction flows and the relay 20 sends a detection signal to a control circuit 21 when the demagnetization current becomes to a level previously set in the relay 20. When the circuit 21 receives the detection signal, the thyristors 13, 15 are made off and the demagnetization current is cut off. This enables to maintain the demagnetization current always at a con stant level irrespective of the variation of the resistance of the coils 6, 7. |
