Abstract: A brushless DC motor is started by initially specifying an arbitrary rotor position and applying such drive currents to the three motor phase inputs that the rotor moves to the predetermined position and thereafter applying a current pulse to the appropriate winding to cause the rotor to move in the desired rotational direction. After the motor has begun to turn, the current supply to the motor phase inputs is interrupted. The current in the motor is allowed to decay to a level where the I and R voltage drops in the windings are substantially less than the back EMFs at the speed at which the motor is turning. The small back EMFs generated in the windings are sampled and monitored to detect whether the rotor has moved to a position requiring a change in commutation. Drive current is supplied to the three motor phase inputs in accordance with whether or not a need for a change in commutation was detected by the sample so that the rotor will continue to turn in the required direction.

Abstract: A head carrier for carrying a plurality of head/arm assemblies each of which comprises a rigid arm portion supporting two flexures biased away from each other and a transducer bearing slider at the free end of each flexure. The head carrier provides the head/arm assemblies in the correct orientation for assembly to the actuator mechanism of a disk file. The head/arm assemblies can be attached to the actuator without removing the carrier.