| 摘要 |
<p>PURPOSE:To previously prevent an overcurrent by detecting a signal corresponding to a primary winding current of a transformer, and detecting a DC bias magnetism by means of a power frequency component in said signal. CONSTITUTION:When a main transformer 100 DC-deflects and magnetizes, the magnetic flux of an iron core in the transformer is saturated either in a positive or a negative polarity the excited current increases and a primary current protrudes on either of the positive or negative polarity. A DC component and the power frequency component exist in the output of a full wave rectifier circuit 20, the AC component is generated in the output of a BPF 21. The component is rectified in a full wave rectifier circuit 22. When the output exceeds a set point, a comparator 23 operates and the DC bias magnetism is detected.</p> |
