Patent ID: 6134126
Filing Date: 2000-10-17
Classification: H02J,H02M,Y02E

Abstract:
A power conversion system comprising:an AC power source;a power converter for converting an AC power supplied from said AC power source into an AC power with a selected frequency in order to individually drive an electric motor; anda noise reduction circuit for detecting a leakage current from a supply line of said AC power source, if any, and flowing a noise compensation current to said supply line of said AC power source;said noise reduction circuit having:an insulating transformer having its primary side connected between said AC power source and said power converter;a rectifying circuit connected to a secondary side of said insulating transformer;positive side and negative side capacitors connected in series between a positive output line and a negative side output line of said rectifying circuit;a connection means for connecting a serial connection point between said positive side and negative side capacitors to a grounded common AC input line arranged upstream relative to said power converter;a positive side switching device having one of its end connected to said positive output line;a negative side switching device having one of its ends connected to said negative side output line and having an ON/OFF characteristic opposite to that of said positive side switching device;a coupling capacitor arranged between the other ends of said positive side and negative side switching devices and the ground; anda switching control means for amplifying a detection signal of said leakage current and applying an obtained amplified signal to the control inputs of said positive side and negative side switching devices.