Patent ID: 6909254

Claim:
A method for stopping sectional drive controllably in connection with a fault situation in the supplying mains, the sectional drive comprising a plurality of inverters which are supplied by a DC voltage intermediate circuit supplied by the mains, a plurality of electric motors which are controlled by the inverters with speed and/or torque control and which are used for implementing speed and tightness reference values of the strip in the sectional drive, the tightness reference value being predetermined motor-specifically or motor-group-specifically, the method comprising, before stopping the sectional drive, an implementing step in which an estimate (T) of the time needed for stopping the sectional drive motors is determined, whereby the method comprises, in connection with a fault situation in the mains, the steps of detecting a fault situation in the supplying mains; forming a deceleration reference value for the motors for stopping the motors within a predetermined time; controlling the speed of the speed-controlled sectional drive motors on the basis of the deceleration reference value; controlling the torque of the torque-controlled sectional drive motors on the basis of a predetermined tightness reference value; determining the magnitude (u) of the DC voltage of the DC voltage intermediate circuit; comparing the magnitude (u) of the DC voltage with a predetermined voltage limit (U dc ); and altering the deceleration reference value on the basis of the magnitude of the DC voltage in such a way that when the determined DC voltage (u) is lower than the voltage limit (U dc ), the deceleration of the motors is increased, or in such a way that when the DC voltage (u) is higher than the voltage limit (U dc ), the deceleration is decreased to stop the sectional drive in a controllable manner, maintaining the tightness reference value of the strip.