| 摘要 |
PURPOSE:To protect a frequency converter without stopping a motor by disconnecting a frequency converter circuit when the temperature of the switching element in the frequency converter becomes higher than a reference value and connecting the AC power source directly to the AC motor. CONSTITUTION:When an operation switch 3M is normally closed, contacts 52 and 52A are excited, and a motor 6 is driven by the output of a frequency converter 3. When the temperature of the switching element in the converter 3 is raised higher than a reference voltage due to the overload operation or the atmospheric temperature rise, the voltage drop of a resistor r corresponding to the reference temperature exceeds the voltage of a temperature detector 7, and the output of a comparator OP2 becomes H level. Thus, a contact 52X is excited, the contacts 52, 52A are deenergized, and the motor 6 is driven directly by the AC power source 1. |
