Patent ID: 6741063
Filing Date: 2004-05-25
Classification: H02P

Abstract:
An inverter apparatus for converting a DC power from an input AC power to an output AC power having a variable frequency and a variable electric power to drive an induction motor at a variable speed, comprising:a rectifying unit for converting an input AC power to a DC power, a filter capacitor for smoothing the DC power outputted from said rectifying unit, an inverter unit having an input connected across said filter capacitor, a motor current detector for detecting a motor current outputted from said inverter unit and a gate circuit for driving said inverter unit; an excitation detection unit for detecting an excitation current of said induction motor from an output of said motor current detector and a reference phase command; a setting unit for setting a limitation level of said excitation current; a torque boost voltage command unit for producing a torque boost voltage command according to an inverter frequency command; and a torque boost voltage compensation unit for changing said torque boost voltage command so that the detected excitation current value is smaller than or equal to said limitation level.