Operating method and control circuit to monitor the start of electric high-voltage motors using asynchronous starting

摘要

A known operating method for the protection of electric motors against overload detects the rotor speed and the supplied power in order to derive an accumulated total value by comparison with stored motor heating values associated with the operating state data, which total value corresponds to the relative heating state of the motor. The new operating method and the control circuit are intended to ensure overload protection for large high-voltage motors where the starting losses are converted in the rotor, for the rotor parts which are affected during asynchronous starting and in the fixedly braked state, taking into account their heating and cooling characteristic, even in the case of these transient processes. In the case of the operating method and the control circuit for monitoring the rotor parts of the high-voltage motor 30 which are affected during starting, the type and duration of the respective operating states (including transient operating states), stator current I1 and speed n are determined and compared with operating state matrices 39, 40. Using a theoretical heating model, the time- dependent dynamic heating characteristic of the rotor parts affected during the starting is represented from said model by means of a heating state matrix 41 by displaying discrete values, by means of which the possible starts are monitored and protective devices 46, 47 are controlled. Brushless high-voltage asynchronous motors, or high-voltage synchronous motors, of high power with asynchronous starting. IMAGE