The ebm-papst EC external rotor motor is made up of five key parts: the motor housing, which protects the electronics and motor winding; the drive electronics, which converts the AC supply voltage to DC and allows the motor to be speed controlled; the motor winding, which is specifically designed for each impeller and motor combination to optimize efficiency; the maintenance-free ball bearings, which do not need to be serviced at all during the life of the product; and the rotor, where the fan impeller is mounted.