Abstract: A control circuit, a system and a method 200 of determining a position of a rotor in a permanent magnet motor PM1 in a state when the rotor is freely rotating, the motor being connected to a direct voltage link 101 via an inverter circuit 102, wherein the inverter circuit is operable for connecting windings of a stator of said motor to the direct voltage link, the method comprising the following a step a) short circuiting 201 the windings of the stator of said permanent magnet motor, a step b) measuring 202 a back electromotive force EMF of the short-circuited windings of the stator; and a step c) determining 203 the position of the rotor by means of the measured back EMF.

Abstract: In a method for controlling a line converter on board a track-bound vehicle semiconductor devices of current valves of the line converter are controlled to be turned on and off so as to prevent the current (I) through a secondary winding of a transformer to which midpoints of phase-legs of the converter are connected to pass zero and shift direction other when the voltage across the secondary winding shifts direction by a start of a new half period of an AC line voltage across the windings of the transformer.

Abstract: A control circuit, a system and a method 200 of determining a position of a rotor in a permanent magnet motor PM1 in a state when the rotor is freely rotating, the motor being connected to a direct voltage link 101 via an inverter circuit 102, wherein the inverter circuit is operable for connecting windings of a stator of said motor to the direct voltage link, the method comprising the following a step a) short circuiting 201 the windings of the stator of said permanent magnet motor, a step b) measuring 202 a back electromotive force EMF of the short-circuited windings of the stator; and a step c) determining 203 the position of the rotor by means of the measured back EMF.

Abstract: In a method for controlling a line converter on board a track-bound vehicle semiconductor devices of current valves of the line converter are controlled to be turned on and off so as to prevent the current (I) through a secondary winding of a transformer to which midpoints of phase-legs of the converter are connected to pass zero and shift direction other when the voltage across the secondary winding shifts direction by a start of a new half period of an AC line voltage across the windings of the transformer.

Abstract: A method of operating a synchronous motor having a stator that includes a set of electromagnets and a permanent magnet rotor. The synchronous motor is controlled by calculating in a flux controller a measure of a flux magnitude, which is the magnitude of the stator flux of the motor and by calculating in a load angle controller a measure of a load angle. Information about a desired motor torque or a reduced motor torque, which is smaller than the desired motor torque, is input to the load angle controller and the load angle controller calculates the measure of the load angle depending on the input motor torque. The measure of the flux magnitude is combined with the measure of the load angle to obtain commands for controlling electric currents of electromagnets of the stator, thereby directly controlling the stator flux.

Abstract: A method of operating a synchronous motor having a stator that includes a set of electromagnets and a permanent magnet rotor. The synchronous motor is controlled by calculating in a flux controller a measure of a flux magnitude, which is the magnitude of the stator flux of the motor and by calculating in a load angle controller a measure of a load angle. Information about a desired motor torque or a reduced motor torque, which is smaller than the desired motor torque, is input to the load angle controller and the load angle controller calculates the measure of the load angle depending on the input motor torque. The measure of the flux magnitude is combined with the measure of the load angle to obtain commands for controlling electric currents of electromagnets of the stator, thereby directly controlling the stator flux.