Abstract: 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.

Abstract: An electric machine element comprises electric terminals (101) for connecting to an external AC system and a multiphase winding (102) comprising at least two multiphase winding portions (103, 104). Each multiphase winding portion comprises phase-windings (106a-106c, 107a-107c) each having a first end (109) and a second end (110). The multiphase winding portions are successively connected to constitute chains (113a-113c) of the phase-windings so that the first ends of the phase-windings of a first one (103) of the multiphase winding portions are connected to the electric terminals. Each multiphase winding portion comprises switches (114a, 114b, 115a, 115b) for connecting the second ends of the phase-windings of the multiphase winding portion to each other. Thus, the number of turns of the multiphase winding is changeable by selecting which one of the multiphase winding portions has a star-point at the second ends of its phase-windings.

Abstract: An electric machine element comprises electric terminals (101) for connecting to an external AC system and a multiphase winding (102) comprising at least two multiphase winding portions (103, 104). Each multiphase winding portion comprises phase-windings (106a-106c, 107a-107c) each having a first end (109) and a second end (110). The multiphase winding portions are successively connected to constitute chains (113a-113c) of the phase-windings so that the first ends of the phase-windings of a first one (103) of the multiphase winding portions are connected to the electric terminals. Each multiphase winding portion comprises switches (114a, 114b, 115a, 115b) for connecting the second ends of the phase-windings of the multiphase winding portion to each other. Thus, the number of turns of the multiphase winding is changeable by selecting which one of the multiphase winding portions has a star-point at the second ends of its phase-windings.