An electric motor includes a stator and a rotor rotatably mounted to the stator. The rotor includes a rotary shaft, a rotor main body attached around the rotary shaft, the rotor main body being rotatable under the interaction between the rotor main body and the stator when the winding is energized. The rotor main body and the rotary shaft are in a loose fitting with each other to allow a rotation speed difference being existed between the rotor main body and the rotary shaft during startup of the rotor. A time-delayed synchronization mechanism is connected between the rotary shaft and the rotor main body and configured to eliminate, with time delay, the rotation speed difference between the rotor main body and the rotary shaft.