Patent ID: 7920395
Filing Date: 2011-04-05
Classification: H02M

Abstract:
1. A power converter which converts a DC voltage fed from a DC power source into a 3-phase variable voltage with variable frequency by turning a plurality of switching elements on and off with a gate signal generated based on a voltage command signal by a pulse width modulation device, and outputs said 3-phase variable voltage with variable frequency to an electric motor for operating said motor in a variable speed control mode, said power converter comprising: a current detection device that detects a current pulse caused by turning on and off said switching elements and flowing on the DC side of said power converter, and determines an entire 3-phase AC current that flows through said electric motor based on said detected DC side current pulse and said gate signal; and a means for correcting a pulse width of a phase voltage in an output of said power converter so that a current pulse width of a DC current may be equal to or larger than a current pulse width enabling a current detection when a difference between voltage command signals for at least two phases among said voltage command signals becomes less than a predetermined value, and outputting said gate signal so that a line voltage pulse for said two phases may be in the form of a combination of different voltage pulses having a reverse polarity.