Induction motor wins new fans

An R&D investment of £2 million by British motor manufacturer Electrodrives has resulted in the development of an innovative `axial air gap induction motor`.

First proposed by the Swiss in the 1940s, the applications for this concept were limited by manufacturing costs and the low strength of the design.

Electrodrives has redesigned the motor using its squirrel cage rotor construction principle and altering its shape by flattening the rotor and the stator. The rotor lies adjacent to the stator and magnetic flux passes across the narrow gap that separates the stationery and moving components.

The width of this air gap must be uniform across its entire plane otherwise performance is compromised and motor noise increases. An SKF bearing arrangement specially designed to cope with higher thrust loads than conventional squirrel cage motors provided the solution to this problem.

SKF’s Hub Unit 1, already widely used in the automotive industry, comprises a double row angular bearing with a spilt inner ring. The unit sits tightly on the rotor shaft and is pre-loaded with a set torque which maintains the air gap specification.

The hub design has enabled the company to produce a motor one-third the length of a conventional induction motor of equivalent power, and its compact dimensions has already won a number of admirers. Within its first year of production the motor has been incorporated into the fan-unit of an air-conditioning system and the company plans to target other applications at a rate of two per year.