Patent ID: 8228019

Claim:
An output filter comprising: a polyphase common-mode filter connected to an output of a power converter at one end; a polyphase normal-mode filter connected to the other end of the polyphase common-mode filter at one end and connected to a motor at the other end; and a capacitor/resistor series-connected body connected to a frame ground of the power converter at one end, wherein the polyphase common-mode filter includes a polyphase common-mode choke connected to the output of the power converter at one end, a first polyphase capacitor connected to the other end of the polyphase common-mode choke at one end, and a neutral-point detecting transformer connected to the other end of the first polyphase capacitor at one end; the polyphase normal-mode filter includes a polyphase normal-mode choke connected to the other end of the polyphase common-mode choke at one end, and a second polyphase capacitor connected to the other end of the polyphase normal-mode choke at one end and having the other ends connected together; the capacitor/resistor series-connected body is connected to the other end of the neutral-point detecting transformer at the other end; and the output filter connects the other ends of the second polyphase capacitor to the one end of the capacitor/resistor series-connected body.