Development and results of an ironless high speed electronically commutated permanent magnet motor

There are some items to be considered when selecting the most suitable kind of motor for a small power high speed spindle application like performance, cost, size, weight, etc. These applications could include aerospatial, automotive and textile industries. Squirrel Cage Induction Motors and Hysteresis Motors can be used, however they present the drawback of having moderate power factor and moderate efficiency (congruent to 70%) which results in a larger motor due the need of more copper in the stator (larger current). In order to obtain a small high speed motor with high efficiency (congruent to 90%) and power factor (greater than or equal to 90%), it was decided to develop an Ironless Electronically Commutated Permanent Magnet Motor (Ironless Motor) with high energy rare-earth magnets. This motor has no iron in the stator and consequently no iron losses. It was designed an Ironless Motor to have a maximum speed of 24000 rpm. The design considered a fixed diameter and used available SmCo5 magnet blocks. Both motors were then analyzed by the Finite Element Method (FEM), and flux lines, flux densities wave forms and values are shown. Experimental electromechanical characteristics of both motors are compared and some conclusions are presented.