An integrated assembly of an electric winding exchanger system and a multiphase electric motor comprises a housing, the multiphase electric motor, and the electric winding exchanger system. Further, the housing comprises a first housing portion, a second housing portion, and a partition. Further, the first housing portion comprises a first interior space and the second housing portion comprises a second interior space. Further, the first housing portion houses the multiphase electric motor and the second housing portion houses the electric winding exchanger system. Further, the electric winding exchanger system comprises a back electromotive force (EMF) boosting circuit comprising switches and bus bars. Further, the partition comprises openings. Further, leads of coils of the multiphase electric motor enters the second interior space through a first opening of the openings for connecting terminals of the leads to the bus bars.

A switching device for an AC motor is a device for controlling switching of an AC motor, and includes a switching unit that switches a connection state of a plurality of phase windings. The switching unit switches between a first state, a second state, and a third state. The first state is a state in which electrical conduction control on first windings of the phases is allowed, and electrical conduction control on second windings is blocked. The second state is a state in which electrical conduction control on the second windings of the phases is allowed, and electrical conduction control on the first windings is blocked. The third state is a state in which electrical conduction control on the first windings and the second windings is allowed.

A converter (101) for driving an electric machine whose stator windings are changeable to be in a low-speed configuration or in a high-speed configuration includes a converter stage (102) for supplying stator voltages to the stator windings, and a control system (103) that controls the stator windings to be in the low-speed configuration or in the high-speed configuration. The control system deactivates the converter stage during a change between the low-speed configuration and high-speed configuration and limits torque of the electric machine so that a torque limit is higher when the stator windings are in the low-speed configuration than when the stator windings are in the high-speed configuration. As the torque limit is changed when the number of series connected turns of the stator windings is changed, unwanted current transients can be reduced.

A controller associated with a power supply determines a first ratio value. The first ratio value may be a ratio of a second time duration with respect to a first time duration, where the second time duration is a measured time duration associated with demagnetizing of a transformer in a first control cycle. The first time duration may be a measured time duration of activating a first switch in the first control cycle, where activation of the first switch operative to control a magnitude of primary current through a primary winding of the transformer. For second control cycle occurring subsequent to the first control cycle, the controller calculates an ON-time duration for activating the second switch based on the determined first ratio value.