Induction Motor for Wide Range Static Inverter Drive: Electrical Machines, Designer's Point of View
A fact, usually overlooked in technical papers is that the design of electrical motors in a.c. drives is highly dependent on the parameters and construction details of the power supplying steady-state conversor, especially on the harmonic content of the applied voltage. The paper outlines some ways of making the motor less sensitive to such harmonics, even when it drives a shaft which is suspended on active magnetic bearings. Attention was shifted from the inverter design to the induction motor design, to ways and means of making the motor immune to changes from one type of inverter to another. The solutions presented are the result of design, manufacturing and extensive testing of a series of induction, squirrel cage electric motors, used in high performance machine-tools (boring and grinding precision machines) with rotating speeds up to 42,000 rpm, with speed control by continuous speed variation. Ratings of electric motors were 0.4; 1.1; 2.2 kw.