| CPC H02P 1/26 (2013.01) [H02P 2207/01 (2013.01)] | 11 Claims |
|
1. A method for starting and stopping an asynchronous motor by a soft starter comprising thyristors connected in antiparallel in switchable phases, the method comprising the following steps:
ascertaining all firing opportunities available for the thyristors of the soft starter at a calculation time in the future;
forecasting, for all the firing opportunities thus ascertained, an electrical and/or mechanical motor behavior corresponding to the firing opportunities;
deciding, based on the motor behavior thus forecast, whether and which firing opportunity is to be chosen;
if a decision has been made to take a specific firing opportunity, generating one or more firing signals for one or more thyristors as a result of which anticipated motor behavior is established;
repeatedly ascertaining a present rotor angle, a present rotor speed, a present grid phase angle, and present stator phase currents;
using the present rotor angle, the present rotor speed, the present grid phase angle, and the present stator phase currents to anticipate a torque response for a torque acting on a rotor for first firing opportunities, in which a firing of thyristors turns on two phases, and for a second firing opportunity, in which firing of thyristors turns on three phases; and
using the torque responses thus anticipated to decide whether each thyristor is fired.
|