Three-phase IEC metric general purpose AC motors operate on three-phase AC power and do not require capacitors to start or run and operate with a higher torque and greater efficiency than single-phase models of the same HP, rpm, and frame size. Motors meet a standard set of electrical, dimensional, and performance requirements based on kilo-watt (kW) ratings. They have metric dimensions and are commonly used in countries outside the U.S. to power compressors, conveyors, fans, and pumps that require International Electrotechnical Commission (IEC) electrical standards. Motors may have a single protrusion on the motor shell such as a conduit box that houses the electrical connections between the external power cables and the internal electrical wiring of the motor.