Electromagnetic clutch in double directions: when the clutch is working, there must be a certain speed difference between the main and slave parts before there is torque transmission. The torque depends on the magnetic field strength and speed difference. The excitation current remains unchanged, and the rotational speed decreases sharply with the increase of torque. The torque remains the same, the excitation current is reduced, and the speed is reduced more severely.

Electromagnetic clutch in double directions due to the main and driven parts without any mechanical connection, no wear consumption, no magnetic powder leakage, no impact, adjust the excitation current can change the speed, used for CVT, this is its advantage. The main disadvantage of the clutch is that the eddy current in the rotor will generate heat, which is proportional to the speed difference. At low speed, the efficiency is very low. The efficiency value is the speed ratio of the main and driven shafts, i.e., η= N2 / N1