| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To detect slight leakage by preventing wrong detection of leakage caused by a primary transient current generated from the load side as charging is started when a battery is charged from an external AC power supply. <P>SOLUTION: The charging monitor including a decision circuit 236, and an electromagnetic relay 11 for interrupting a load section 50 having a battery 53 and an external AC power supply when a decision is made that leakage has occurred is further provided with a zero-phase current transformer 12 outputting a voltage signal dependent on a level difference of currents flowing through AC lines L1 and L2 across a coil, a neutral ground circuit 231 for suppressing a DC component included in the voltage signal across the coil, a differential amplifier 232 for amplifying the voltage signal across the coil as a difference from the ground, a low-pass filter 233 performing level conversion of the voltage signal in correspondence with the leakage characteristics, a DC cut filter 234 for cutting the DC component from the output of the low-pass filter 233, and a circuit 235 for rectifying and smoothing the output of the DC cut filter 234. <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
