ABSTRACT
Induction machines form the bulk of the electrical drives used in industry by virtue of their combination of simplicity and robustness. The majority of AC variable speed drives are based around the use of an inverter to provide a variable frequency supply to an induction motor. Brushless machine can be operated either as a synchronous machine, receiving a multiphase variable frequency supply, or as a DC machine, in which case the commutation of the stator currents would be performed electrically. The gear motors are employed on low power drives up to about 20 kW, such as for cooling fans on diesel locomotives, located in the roof panels where space is at a premium. Piston-type pneumatic motors are used quite widely in V or in-line configuration as starter motors for diesel engines, environment where they do not need to be subject to any form of speed control beyond that which can be provided by a simple pressure control or flow restriction.
