A single-phase power supply connected to an AC motor uses additional circuitry for starting because it will not produce a rotating magnetic field. The standard frequency of single-phase electrical systems is usually 50 or 60 Hz. Electric railways use 16.67 Hz in special single-phase traction power systems. The Neckarwestheim nuclear power plant (located in Germany) is the largest single-phase generator in the world and is used to power a railway system on dedicated traction power.