INVERTER CONTROLLER FOR INDUCTION MOTOR

摘要

PURPOSE:To prevent an induction motor from entering into free-run state by lowering the frequency of output voltage upon DC voltage drop at a converter section due to power interruption or instantaneous power interruption and feeding regenerated power from the induction motor side. CONSTITUTION:DC voltage at a converter section 4 beings to drop gradually upon power interruption or instantaneous power interruption. DC voltage at the converter section 4 is monitored through a voltage monitoring means 9 and a power interruption detecting means 10 decides power interruption when the DC voltage drops below a reference level. Upon receiving a power interruption detection signal from the power interruption detection means 10, a frequency output means 11 decreases the frequency by an amount reversely proportional to the frequency of the power interruption detection signal and operates an induction motor 13 as a generator in order to supply regenerated power. According to the constitution, the induction motor 13 is prevented from entering into free-run state upon power interruption or instantaneous power interruption.