The detection method of the stop position of the rotor in brushless DC motor does not have a position detector

摘要

PURPOSE:To reduce power consumption by detecting the relative position of the position of the magnetic pole of a rotor and a three-phase winding by a conductive pattern, from which a measured voltage value is obtained. CONSTITUTION:Conduction at 180 deg. to star-connected three-phase windings U, V, W is made conductive successively by each of six kinds of conductive patterns. Consequently, the relative positional relationship of the positions of magnetic poles formed by magnetization to a rotor 30 under the state of stoppage and the locations of three-phase windings U, V, W can be determined according to the states of six neutral-point voltage values at the transient time measured discretely at a neutral point Pcom in response to conduction by six kinds of the conductive patterns. That is, a control signal is transmitted over a commutation control circuit 4 from a controller 1, and the commutation control circuit 4 is operated so that conduction at 180 deg. to the three-phase windings U, V, W is performed successively to each of six kinds of the conductive patterns at every predetermined short time set to a timer 3.