Design of a high-speed permanent magnet motor

The authors describe the design of a high-speed hand-held precision instrument suitable for surgical work in dentistry and medicine. This instrument is capable of delivering 10 W to the cutting tool at a speed of 150000 r.p.m. The final design is somewhat unusual and consists of a miniature synchronous motor having a rare-earth cobalt rotor magnet of only 3 mm diameter and 7 mm axial length. The 3-phase motor is supplied at 2.5 kHz by three in-line transformers having single-turn secondary windings which are connected to the motor stator winding. This consists simply of three bars and an end-ring and is machined as a single component