Switched reluctance (SR) drives are relatively new forms of brushless drive which eliminate the need for any rotor conductors or permanent magnets. They operate on forces of magnetic attraction and consequently need only unidirectional stator-winding currents which results in a particularly economical and robust electronic controller.
Despite this simplicity and robustness, SR drives can more than match the attractiveness of fully-controlled dc systems; and in terms of specific torque and power densities, efficiency, permissible speeds, dynamic response and thermal behaviour, their performance levels generally exceed those of induction, dc and universal motors.
Fig. 6 is illustrative of this for a general purpose industrial drive in terms of efficiency, torque and power output, low-speed performance and constant power range. The paper discribes similar qualities in applications and sizes for household appliances, traction, compressors and more generally; and it outlines why manufacturing costs are very competitive.
Initially, the novelty of SR drives, and their contradiction of received wisdom about the fundamental capacities of electrical machinesgenerally, slowed their acceptance in both industrial and academic spheres. That position is now completely changed, and large scale developments are in hand worldwide for many new products.
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