Patent ID: 7511439

Claim:
A method for starting a sensorless, electronically commutatable direct current motor, having a permanent-magnetically excited rotor and a stator that carries a multi-phase, in particular three-phase stator winding, as well as having a switching device, controlled by a control device, for supplying current in the correct order to the phase windings of the stator from a direct voltage source, the method comprising at rotor standstill and at the onset of the startup operation in the range below a minimum value of the rotor rpm, first the position of the rotor is ascertained by the control device, and then via the switching device, a regulated initial supply of current to the phase windings of the stator is effected, while after the predetermined minimum value of the rotor rpm is attained, the control device receives position signals as rotor position signals for a self-commutation of the motor, which signals are derived directly from the third and/or further odd-numbered harmonics of the phase voltages, and from these position signals furnishes control signals to the switching device for supplying current to the phase windings in normal operation and further comprising driving the third and/or the further odd-numbered harmonies of the phase voltages of the stator, on the one hand via the star point of the phase windings and on the other via an auxiliary star point, formed of three phase resistors, to a comparator with a downstream integrator.