Patent ID: 8183817

Claim:
A winding switching apparatus for switching windings of an AC three-phase motor, the winding switching apparatus comprising: an AC three-phase motor having windings for the respective three phases, the windings each having an intermediate tap, a winding start terminal, and a winding end terminal that are provided outside the AC three-phase motor; an inverter configured to supply a variable voltage having a variable frequency to the winding start terminals; a plurality of winding switching sections configured to switch the intermediate taps and the winding end terminals; and a plurality of drive circuits each configured to receive a drive signal from the inverter and control the corresponding winding switching section, wherein the winding switching sections each include: a diode unit having three diodes whose cathodes are connected to each other; a switching unit having three power semiconductor switches and three diodes connected in inverse parallel to the respective power semiconductor switches, wherein emitters of the respective power semiconductor switches are connected to each other, collector of the respective power semiconductor switches are connected to respective anodes of the diodes of the diode unit, and connection points between the respective collectors of the power semiconductor switches and the corresponding anodes of the diodes of the diode unit are connected to the respective winding end terminals or to the respective intermediate taps; a potential fixing unit having a positive-side charging resistor, a capacitor, and a negative-side charging resistor, wherein one end of the positive-side charging resistor is connected to a positive-side DC bus of the inverter, the other end of the positive-side charging resistor is connected to a positive side of the capacitor, a negative side of the capacitor is connected to one end of the negative-side charging resistor, the other end of the negative-side charging resistor is connected to a negative-side DC bus of the inverter, and the positive side of the capacitor is connected to the cathodes of the respective diodes of the diode unit; and a protective diode unit having three diodes whose anodes are connected to the negative side of the capacitor of the potential fixing unit and whose cathodes are connected to the respective connection points between the respective anodes of the diodes of the diode unit and the corresponding collectors of the power semiconductor switches of the switching unit.