Abstract: A load monitor for monitoring the load of a motor comprises a Central Processing Unit (CPU) and a memory. During normal operation of the motor, the load monitor is arranged to repeatedly measure the torque and registering the speed of the motor. In connection with each measurement of the torque and registering of the speed, the load monitor determines a load limit value valid for the registered speed, which load limit value is a function of a plurality of torques and speeds and a predetermined deviation value stored in the memory. The measured torque is then compared with the determined load limit value and if the measured torque is not within an acceptable range limited by the determined load limit value then an appropriate action is taken.

Abstract: A control device for electric motors and a method for monitoring the serviceability of a transmission part arranged for transmission of torque between an electric motor and a load during operation. The method comprises the steps of initiating at least one test sequence, and sending a signal indicating an error if said at least one test sequence indicates that the serviceability of the transmission part is not acceptable and if no further test sequences are to be performed. Additionally, said at least one test sequence includes the steps of setting a rotation speed of the electric motor at a test rotation speed, which differs from the rotation speed of the electric motor immediately prior to said setting, and measuring at the electric motor, within a period starting from the setting of the rotation speed of the motor and ending when the rotation speed of the electric motor has reached the test rotation speed.

Abstract: A load indicator for an electric motor, comprising a first means (II, IU, CPU) for repeated determination of the motor load, a second means (CPU) for comparing the current motor load, as determined by the first means, with a preset load limit, and a third means (CPU), PP) for indicating that the current motor load exceeds the load limit. Moreover, a meant (T, CPU) is arranged to initiate a presetting of the load limit. This means is adapted to be actuated, when the motor runs in normal operation, for presetting of the load limit as the current motor load changed by a predetermined deviation value stored in the load indicator.

Abstract: The invention relates to a process for estimating an instantaneous resistance in a phase winding in a reluctance machine. The process comprises the steps of: receiving a signal indicating a voltage across at least one phase winding; receiving a signal indicating a current through the phase winding; estimating a magnetic flux in response to the voltage signal and the current signal; estimating an instantaneous resistance in the phase winding in according with a phase relation between the current signal and the magnetic flux signal. The invention also relates to a method for controlling an electrical machine and a drive system for performing the method.

Abstract: A control circuit for a reluctance machine having two mutually movable parts and at least one inductive phase winding adapted for a certain maximum drive current value. The method includes detecting when a phase winding is in a non-drive mode; causing a test current, having a second maximum value lower than said certain maximum value, to flow through the phase winding and through a current sensor when the winding is in the non-drive mode; and establishing a mutual position in dependence of the output of said current sensor.

Abstract: The invention relates to a process for estimating an instantaneous resistance in a phase winding in a reluctance machine. The process comprises the steps of: receiving a signal (Udm) indicating a voltage (UW) across at least one phase winding; receiving a signal (iWm) indicating a current (iW) through the phase winding; estimating a magnetic flux in response to the voltage signal and the current signal; estimating an instantaneous resistance (RW) in the phase winging in accordance with a phase relation between the current signal (iWm) and the magnetic flux signal (&PSgr;est). The invention also relates to a method for controlling an electrical machine and a drive system for performing the method.