Induction motor system with an induction motor and an electrically isolated voltage modulation motor controller

摘要

An induction motor system operable in a wet environment comprises an induction motor and an apparatus for controlling the speed of the motor. The motor is adapted to be coupled to an AC source for supplying an AC signal. The motor includes a rotor having rotor laminations. The reflected rotor resistance over reflected rotor reactance ratio of the motor is adjusted to be greater than one. The controlling apparatus includes a switching device, user controls, controller means and isolation means. The switching device is connected in series with the motor and is operative in either a high impedance state wherein significant current flow through the motor is prevented or a low impedance state wherein current flow through the motor is substantially undisturbed. The user controls provide motor speed input signals. The controller means receives the motor speed input signals from the user controls, and switches the switching device between its low and high impedance states in a predetermined sequence for inducing a phase angle delay in the AC signal. The isolation means electrically isolates the controller means from the AC source and includes coupling means for optically coupling the switching device to the controller means.