The electromagnetic brake automatically adjusts the braking as follows: 1. The braking torque generated by the electromagnetic brake (i.e. eddy current retarder) can be adjusted by the excitation current control device. The greater the excitation current through the coil, the stronger the magnetic field and the greater the braking torque; 2. When the current of the electromagnetic brake is cut off, the brake pad is separated from the brake disc, a friction torque is generated between the brake pad and the flange, and the transmission shaft is used to stop quickly; 3. When the current passes through the electromagnetic coil of the electromagnetic brake, the electromagnetic force attracts the brake pad, and the brake disc is released by the brake pad. At this time, the transmission shaft runs normally or starts with a brake disc; 4. It is usually used for high-speed braking of vehicles, but the effect of low-speed braking is not ideal, and it is usually used in combination with conventional friction braking.