Loss measurement of a 40 kW high-speed bearingless PM synchronous motor

The losses and the temperature rise of a high-speed “bearingless” permanent magnet (PM) synchronous motor prototype, designed for 40 kW at 40,000 rpm, represent the focus of this paper. A combined axial-radial permanent magnet (PM)-biased homo-polar magnetic bearing is responsible for the magnetic levitation along the axial and the drive-end (DE) radial direction. The “bearingless” motor unit supplies the torque and the radial magnetic suspension of the non-drive end (NDE). Thus, the losses of such a drive can be divided in two main categories: motoring losses and magnetic suspension losses. These losses are calculated analytically and numerically and their values are verified through no-load and load measurements on the constructed prototype.