SPEED-VARIABLE DRIVING DEVICE FOR INDUCTION MOTOR FOR JET FAN OF ROAD TUNNEL WHICH IS DRIVEN THROUGH LONG CABLE

摘要

PROBLEM TO BE SOLVED: To solve an insulation degradation problem with a motor caused by switching surge of an inverter which may occur when an induction motor for a jet fan is driven through a long cable, an EMI problem of a high frequency band, an influence of voltage drop caused by a circuit construction at the secondary side of an inverter device and the long cable.SOLUTION: An inverter device 130, an in-phase reactor 140 and an AC reactor 151 are provided, a start-connected first capacitor circuit 152 is connected in parallel at the rear side of the AC reactor 151, a terminal voltage of the first capacitor circuit 152 is supplied to an induction motor 400 for a jet fan through a long cable 300, the middle point of the start-connection of the first capacitor circuit 152 is connected to the neutral point of an AC/DC converter 131, etc., and the in-phase component of the AC/DC converter 131 and the in-phase component of the inverter circuit 132 are circulated to reduce the in-phase voltage. An adjusting transformer 180 is inserted to eliminate the influence of voltage drop caused by the circuit at the secondary side of the inverter device 130 and the cable 300, and the input voltage of the induction motor 400 for the jet fan is adjusted to be close to a rated input voltage.