A new non-contact drive system has been developed employing a consequent-pole type bearingless permanent magnet (PM) motor and a thrust magnetic bearing. This bearingless motor has a wide magnetic gap. The wide magnetic gap may cause a decrease in radial magnetic suspension force because of an increase in magnetic reluctance. A thrust magnetic bearing is installed at the end of the shaft, because strong thrust force exists in centrifugal pump applications. In this paper, the magnetic suspension forces and rotation characteristics of the experimental prototype are evaluated, while the rotor is magnetically suspended. Experimental results are also compared to the calculated ones using the finite element method. It is demonstrated that the developed consequent-pole type bearingless PM motor possesses sufficient magnetic suspension force for non-contact operation.

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A wide magnetic gap consequent-pole type bearingless motor has been developed. The wide magnetic gap makes it difficult to start up and suspend a shaft with reasonable suspension voltage and current. To provide high current, high voltage rating is demanded, although, high voltage causes bad influence on magnetic suspension. In this paper, the authors have investigated the start-up and rotational characteristics of a prototype bearingless machine driven by voltage source inverters having the rated voltage of 200V and 100V. When the rated voltage is not suitable, significant problems are occurred. The effectiveness of proper selection in the rated voltage is discussed. The result of this study shows that the 100V inverter is a better choice for the bearingless motor.

Developments of high speed motor drive have been described. A switched reluctance motor has been designed for 2kW output at a rotational speed of more than 100,000r/min. A test machine has been constructed based on the design. The iron parts are fabricated by 6.5% silicon steel, i.e., low iron loss material. The rotational speed of 150,000r/min is reported experimentally. Fast and accurate controller has been developed using field programmable gate array device.Index Terms-Field programmable gate array, high speed motor, switched reluctance motor.