Commutator Machine

an electric machine, such as a generator or motor, in which the rotor winding is connected to a commutator. A distinction is made between DC and AC machines. DC commutator machines are widely used, but the presence of a commutator limits their power to several megawatts and their voltage to 1.5 kilovolts. In AC machines, the commutator serves as a mechanical frequency converter.

Commutator generators are used mainly to supply three-phase alternating current; they make possible control of the current frequency independent of the speed of rotation of the generator rotor. Single-phase and three-phase commutator motors, in contrast to squirrel-cage motors, have flexible control characteristics but are also more expensive, heavier, and less reliable. Low-powered single-phase motors are widely used in household appliances. Three-phase motors with power ratings up to several kilowatts are used mainly in power drives with a wide range of speed control. Commutator frequency converters are components of dynamoelectric stages; they are also used for voltage and current phase shift compensation in asynchronous motors. The development of semiconductor technology brought about substitution of the more promising static frequency converters for commutator machines.