A device has a plurality of power converter groups and a control system. A power converter group has a group of power converters and is coupled between an input voltage source and a group of windings of a motor generator. The control system is configured to control currents of the windings such that the number of poles of and the number of phases in a pair of poles of the motor/generator are dynamically adjusted, and the number of poles and the strength of a magnetic field of the motor generator are controlled to reduce a power loss. The motor/generator has an air gap and a stator with a plurality of slots, where the windings are installed in. The windings are configured such that the number of poles and the number of phases in a pair of poles of the motor/generator can be dynamically adjusted.