The structural advantage of this model lies in a permanent cylindrical magnet as the rotor with a very small air gap. The magnetic flux of the permanent magnet flows in the direction of the dotted arrow. When the coil is energized in the direction shown in Fig. 1, the magnetic flux induced by the coil current flows in the direction of the dot-and-dash arrow. While the two magnetic fluxes increase in the magnetic air gap and decrease in the magnetic air gap, the rotor-driving rotational torque acts in the clockwise direction.
