Three Phase Supplies

In most industrial and commercial premises the large amount of electrical power requires the use of 'Three Phase' electrical supplies.

The main electricity companies will supply the three phase AC voltage direct to the customer premises.

Three Phase electricity uses higher voltages than the 240volts normally encountered in domestic premises and offices. Each phase will supply 415 volts, phase to phase, against the domestic supply of 240 volts phase to neutral. This creates a greater hazard when working around three phase supplies.

The individual conductors should be labelled as Phase 1, Phase 2, Phase 3, Neutral (N) and Earth (E). However it is possible that the phase colour designation (Red/ Blue/ Yellow) may still be encountered.

• Voltages quoted are for UK supplies, they may be different in other countries, but will maintain the same relationships.

There are two configuration options with three phase supplies - star and delta connections. Both are in common use.