Three phase power is a method of electric power transmission using three wires. Three phase power systems may have a neutral wire that allows the system to use a higher voltage while still allowing lower voltage single phase appliances. In high voltage distributions, it is not common to have a neutral wire, as the loads can simply be connected between phases.

Three phase power is a very efficient form of electrical power distribution. All three wires carry the same current and have a constantly balanced power load. Three phase power does not generally power domestic houses, and when it does, a main distribution board splits the load. Most domestic loads use single phase power.

Conductors used in the three phase power system are color-coded. Most countries have their own color codes. The color codes of the wires vary greatly. There may be a standard for each installation, or there may be no standard at all.

Three phase power flow begins in a power station. An electrical power generator converts mechanical power into alternating electric currents. After numerous conversions in the distribution and transmission network, the power is transformed into the standard mains voltage. At this point, the power may have already been split into single phases or into three phases. With three phase power, the output of the transformer is usually star connected with the mains voltage, 230 volts in Europe and 120 volts in North America.

Electric motors are the most common use for three phase power. A three phase induction motor combines high efficiency, a simple design and a high starting torque. Three phase electric motors are commonly used in industry for fans, blowers, pumps, compressors and many other kinds of motor driven equipment. A three phase power motor is less costly than a single phase motor of the same voltage and rating.

Other systems that use three phase power include air conditioning equipment, electric boilers and large rectifier systems. The main reasons for using the three phase power system are efficiency and economy. While most three phase motors are quite big, there are examples of very small motors, such as computer fans. An inverter circuit inside the fan converts DC to a three phase AC current. This serves to decrease noise, as the torque from a three phase motor is very smooth, and it also increases reliability.