Developments on bearingless drive technology

Meanwhile the bearing-less motor technology offers a lot of mechanical and electrical design variants for various kinds of applications. A comparison of switched reluctance motor, asynchronous motor and permanent magnet motor technology shows advantages and disadvantages with regard to different technical requirements. Especially for small motor applications with large air gaps the permanent magnet motor is of great importance. This is confirmed by a comparison of electromagnetic and permanent-magnetic pole designs. Based on bearingless permanent magnet motors with integrated winding systems for levitation as well as torque generation reliability and-fault-tolerant design studies are carried out. It is shown that with an appropriate motor design a failure of an arbitrary phase can be compensated by the motor itself. In such a case there is no need for failure detection in order to switch over to special auxiliary control algorithms. A further advantage of the integrated winding system is the high grade of copper utilization independent of the ratio of radial force and torque loads.