Brushless motor fed from DC source - has auxiliary start up circuit ensuring correct run up direction

摘要

The motor is wound with three stator phases to which current is switched sequentially by an operational amplifier and power transistor circuit. An additional winding on the stator provides the necessary positional information for the switching circuit. To ensure the correct run up direction a time delayed control element is added which produces three outputs lasting for the start up period (t0-t2). The first lasts the whole period and earths the amplifier inputs, thus rendering the sequential switching inoperative. The second lasting a s shorter time (t0-t1), switches on two motor phases to bring the permanent magnet rotor to a known starting position. The third follows the the second (t1-t2) in time. It switches on the other phase of the motor thus causing rotation in the required direction.