| 摘要 |
PURPOSE:To protect a motor from burning, by providing a electronic circuit for detecting current flowing through a compressor motor and obtaining a DC voltage proportional to the variation of the motor current then producing a time delay and judging overcurrent thus interrupting a solenoid switch. CONSTITUTION:Voltage to be induced in current transformers CT1, CT2 arranged at a current detecting section 11 increases as the motor current increases, and the voltage is rectified at a DC converting section 12 and applied onto a capacitor C1 at a maximum value detecting section 13 thus maintaining the peak value. The peak voltage E1 held in the capacitor C1 is time delayed at a time delay producing section 14, then a capacitor C2 is charged with the time delayed peak voltage E1. When the charged voltage E2 of the capacitor C2 exceeds over a reference voltage E3 at an overcurrent judging section 15, output from a comparator IC1 is turned ON. Consequently, a relay contact 16' is turned OFF to interrupt power supply to the drive coil L1 of a solenoid switch 1, and normal close contacts S11, S12, S13 are turned OFF to stop operation of a compressor motor 3 thus protecting the motor from burning due to overcurrent. |
