The present invention provides an auxiliary excitation winding set to be installed at the rotary part of the electric machine (104) composed of a rotary part of the permanent magnetic electric machine or a rotary part of the reluctance electric machine of the switched DC brushless electric machine (1000), and an electric conductive annular brush device (107) is served as an interface for transmitting the electric power, thereby inputting the excitation electric power to the auxiliary excitation winding set; and through controlling the value and the polarity of excitation voltage and current, the magnetic pole of the rotary part of magnet-motive electric machine (104) of the switched DC brushless electric machine (1000) can be performed with the excitation effect of auxiliary excitation or differential excitation or auxiliary compound excitation or differential compound excitation.