METHOD FOR HOLDING THE ROTARY POSITION OF A ROTOR OF A PERMANENTLY EXCITED THREE-PHASE MACHINE HAVING A SOFT STARTER, TO WHICH ROTOR AN EXTERNAL TORQUE IS APPLIED, AND THREE-PHASE MACHINE

摘要

In order to achieve the energy efficiency class IE4 defined in IEC standard 60034, it is necessary to operate permanently excited synchronous machines directly from the mains. Since this is not readily possible, soft-starting devices come into consideration as cost-effective solutions. The invention relates to a method by means of which a rotor of a permanently excited three-phase machine (M), to which rotor an external torque is applied, can be held. In said method, two phases (U, V, W) have current pulses applied and at least one electric characteristic variable of the three-phase machine (M) is determined. The at least one electric characteristic variable is evaluated in order to draw conclusions about a static or a rotating state of the rotor (L), depending on a value or a time/value profile of the at least one electric characteristic variable. If it is determined that a rotating state of the motor (L) is present, countermeasures are initiated.