| 摘要 |
<p>Disclosed is an overvoltage protection circuit which interrupts power supply with a simple configuration by detecting an overvoltage applied to even a load of high electric power consumption. A first relay contact (14b) is connected between a polyphase power supply (12) and a compressor (16), and a first relay coil (14a) for controlling open/close of the first relay contact (14b) is provided in a control circuit (100) which consumes electric power less than the compressor (16). A second relay (140) is connected between the polyphase power supply (12) and a control circuit (100). When an overvoltage detection circuit (22) detects an overvoltage, a relay drive section (24) controls the energization of a second relay coil (140a) in the second relay (140) to cause interruption operation, thus interrupting power supply from the polyphase power supply (12) to the control circuit (100). When power supply to the control circuit (100) is interrupted, power supply to the first relay coil (14a) is also interrupted and the first relay contact (14b) performs an interruption operation.</p> |
