Brushless dc motor

As being mostly used as a spindle motor, such as a hard disk drive or a laser scanning unit of a computer, a brush-less of the improved 10-pole 9 slot direct current motor has been disclosed in order to improve the reduction of the cogging torque and driving torque. By the motor are 10 magnetic poles having an armature wound around the final coil in an iron core having an annular permanent magnet which is magnetized in the radial direction, and 9 each formed dolgeuk the slot to a three-phase for a field in, a three-phase to obtain a rotational force by making the rotating magnetic field connection coil. According to this motor cogging torque cycle at the time of rotation is short, and its value is also significantly reduced reliability, and low ripple of the drive torque is good efficiency, large in size.