| 摘要 |
<p>A sensing conductor formed by an uninsulated wire (W) is arranged in the appliance to sense leakage current to earth if the appliance gets wet. A solenoid or double-pole double throw relay (R) connects with a modified bridge circuit between the two power supply lines and through the sensor wire to earth. The relay contacts are latched into the normally-open (NO) position when an electrical path exits between the sensor wire and earth. When power is turned on and the relay is connected to the normally closed contacts (NC) and the leakage current rises above a threshold value, the sensor wire connects either power lead to earth. The relay closes to the normally open contacts and latches, to remove power from the appliance. The relay stays latched until it is disconnected from the power source.</p> |
