Principles of Operation
When power to the magnetic coil is cut the magnetic field on the yoke collapses and the plate is no longer attracted. It is pulled back by the spring and motion transmission is cut.
When the magnetic coil is energized the yoke is magnetized and draws the armature plate over. This causes friction between the lining on the yoke and the armature, and the clutch is engaged.
Actions of the brake and spring: