| 摘要 |
<p>PURPOSE:To prevent the deterioration of circuit elements incorporated in an inverter-motor running under light loads by stopping the motor by a method wherein voltage/frequency conversion circuit input voltages as well as excess voltages and currents are detected. CONSTITUTION:Excess voltage detecting units 27-29 for detecting excess voltages yielded by a converter circuit, excess current detecting units 32 and 33 for detecting excess currents flowing into the switching circuit 27, and a voltage/ frequency conversion voltage detecting unit 39 for detecting that a voltage inputted into a voltage-frequency conversion circuit is higher than a standard level, are provided. Satisfaction of AND conditions for the outputs A-D of the detecting units, that is, when the inverter-motor is placed under a lightened load while in a high speed operation, a switching circuit 37 is turned OFF by a signal from a control signal circuit 36. The system being thus constructed, the inverter- motor is stopped when the load becomes light while it is in a high-speed operation, which prevents the shortening of the service life of all the components incorporated in the inverter-motor.</p> |
