| 摘要 |
PURPOSE: To extend the life of a pump motor by constantly maintaining an ambient temperature at normal temperatures and driving a pump motor and stopping the drive automatically when the pump motor is driven, when it is overloaded or unloaded exceeding a specified time period. CONSTITUTION: The drop in the ambient temperature of a pump motor PM below zero is detected, a heater H is automatically driven by the detection signal, and the ambient temperature of the pump motor PM is constantly maintained at normal temperatures, and current that flows into the pump motor PM is detected by a voltage. Then, when the detection voltage is maintained continuously for a specific amount of time at a specified value or higher or at a specified value or lower than a rated voltage at the normal operation of the pump motor PM, the drive of the pump motor is stopped automatically. |
