A motor assembly including a motor and a control circuit board. The motor includes a housing, a stator assembly, a rotating shaft, and a rotor assembly. The control circuit board includes a first electric wire, a second electric wire, a detection wire, a ground wire, a power supply circuit, a control circuit, and a detection circuit. The first electric wire and the second electric wire are connected to the commercial AC electric supply, and the detection wire detects whether or not a load connected to the motor is electrified. The first electric wire and the second electric wire are connected to the input terminals of the power supply circuit. The detection circuit is disposed between the detection wire and the ground wire. The detection circuit transmits a detection signal to the control circuit, and the control circuit controls the motor to rotate at various rotation speeds.