With the exception of single-phase motors, the vast majority of motors, as well as shaded and repulsive motors, can be used in both directions of rotation, varying only a specific control. In the case of AC motors, with the exception of universal motors, they are constant speed machines. It should be emphasized, however, that there is a possibility that the stator coils of an induction motor can be re-coupled so that it doubles the number of poles. Among the main functions of the control of a motor are starting, direction of rotation, stop, speed regulation, starting current limitation, mechanical protection and electrical protection, among others.
An engine only starts its spin at the instant of the load to be overcome, when stopped, is less than its starting torque. In some specific applications there is a need for a rapid deceleration of the engine general motors leeson and the load. When turned off the power line motor uses a rotation reversing device with the motor still running. Switching off the mains motor or stopping is done by means of a device, thus preventing it from starting in the opposite direction. In the case of synchronous motors dynamic braking is counted.