INVERTER APPARATUS

PROBLEM TO BE SOLVED: To reduce power consumption during deceleration of an induction motor when blackout occurs and to sufficiently secure residual energy for completely stopping the induction motor. SOLUTION: When blackout occurs during a regular operation, a mode switching part 10 sets a system to a carrier frequency reduction mode. A driving frequency fCand a carrier frequency fDof an output driving signal IDof an inverter circuit part 5 are sequentially reduced by a PWM signal SPWMfrom a PWM signal generating part 12, and the induction motor 7 is deceleration-braked. During deceleration braking, a smoothing capacitor 3 is charged by regenerative energy supplied from the induction motor 7 through the inverter circuit part 5. Although the induction motor 7 is deceleration-driven by DC voltage VCand the PWM signal SPWMby charging, the carrier frequencies are sequentially reduced. Thus, power consumption in the inverter circuit part 5 is reduced, and energy for DC braking which completely stops the induction motor 7 which is sufficiently decelerated can be left in the smoothing capacitor 3. COPYRIGHT: (C)2009,JPO&INPIT