TEST PROCEDURE FOR VERY HIGH-SPEED SPINDLE MOTORS

In the last ten years, the new power electronic devices and the new co ntrol techniques have allowed to open new application fields for adjus table speed/torque electrical drives. Although the traditional de driv es keep still the market supremacy, the new ac drives have performance really attractive and some additional benefits due to the machine str ucture and to the maintenance costs. Usually, ac drives use induction or brushless motors and the power amplifiers are driven by variable vo ltage/frequency in order to obtain variable speed. The authors deal wi th induction motors fed by non conventional supplies at very high freq uency. In order to evaluate the total motor losses and the single item s, a test bench with a synchronous machine capable to work up to 2 kHz with sinusoidal output voltage has been set up. As a consequence, an induction motor equivalent circuit with parameters depending on the fr equency has been proposed. Today, the empirical procedure is that to u se for high frequency applications shelf motors derated of a factor 10 to 20 % in order to keep into account the extra harmonic losses. On t he other hand, the authors propose to design 'ad hoc' the motors for s ix-steps continuous operation in order to get about the same efficienc y of standard motors. The new proposed motor equivalent circuit togeth er with the test procedure seem to be a practical tool in order to aid the new motor design.