Method for controlling rotational torque on e.g. passive electromagnetic brakes in lifts, involves determining reference value for current that is applied to coil in relation to desired rotational torque for applying to coil

摘要

The method involves monitoring a current value (I) in a coil (12) after switching off voltage (U) in the coil. A value of current intensity is determined at a time point when an armature disk (20) is released from a magnetic element (10). Length of distance traveled by the armature disk is determined from a difference between two measured currents. A reference value for the current applied to the coil is determined in relation to a desired rotational torque that is smaller than maximum torque, is determined and applied to the coil.