Patent ID: 8138702

Claim:
A method for controlling an electric motor with a softstarter device, the method comprising: determining an electromagnetic motor torque of said motor in motion, calculating a difference between said determined electromagnetic motor torque and a reference torque value for said electromagnetic motor torque, calculating a torque error signal from the calculated difference between said determined motor torque and the reference torque value, controlling the motor torque in dependence of said torque error signal, so that the motor torque has a rate of change with respect to time, during a stopping or starting time interval, that is adapted to follow a rate of change of the reference torque value, wherein the rate of change of the reference torque value varies between at least a first part of the time interval and a second part of the time interval, thereby changing the speed of said motor, calculating the rate of change of the motor torque based on a measurement of an input voltage supplied to the motor, and taking the measurement of the input voltage supplied to the electric motor from an inline position before the softstarter device.