Patent ID: 8766574

Claim:
A method for operating a three-phase brushless direct current motor ( 2 ), the direct current motor having phase windings fed by an inverter connected to a voltage source with a high potential side and a low potential side, the inverter having semiconductor switches arranged in bridge branches of a bridge circuit, and the semiconductor switches are controlled such that each phase winding has a 120° commutation angle and current always flows through two respective phase windings during motor operation, the method which comprises: operating the direct current motor with normal commutation when a rotational speed thereof is greater than or equal to a minimum rotational speed; during motor operation with normal commutation, offsetting the commutation angles referred to the respective phase winding by an angular amount of 60° and over a 360° cycle, producing an electrical connection to the high potential side for 120°, followed by a 60° angle without electrical connection, followed by a 120° angle with electrical connection to the low potential side, and followed by a 60° part-cycle without electrical connection for each bridge branch with associated phase winding; and during motor operation in start-up mode, up to the minimum rotational speed of the direct current motor, during a connection of a semiconductor switch to the high potential side, shifting a commutation of a phase winding on the high potential side with respect to a commutation of the respective phase winding on the low potential side during a connection of a semiconductor switch to the low potential side by an angular amount greater than 0° and less than or equal to 60° between a beginning of the commutation on the high potential side and a beginning of the commutation on the low potential side of the respective phase winding for all phase windings, as referred to the normal commutation.