This invention is concerned with dynamo-electric machines of the commutating type combined with an integral speed sensor, producing a speed sensitive signal usable to measure or control the speed of the machine.
Speed sensing devices for dynamo-electric machines are well-known in the art. Among the best and longest known are centrifugal devices and tachometer generators. Centrifugal devices are inaccurate and subject to failure due to the effects of friction, wear and fatigue. Tachometer generators are relatively expensive. More recently magnetic pick-ups and optical sensors have been employed to sense speed. These latter sensors generate the pulses required for digital controls. Both are relatively expensive. Less expensive sensing devices are desirable, especially for use with small machines.