Three phase power supply is a commonly used form of electrical power supply for large installations like factories, offices and other that demand unhindered electric power. Three phase power is a common form of electrical power supply for larger electrical installations and a popular method of electric power transmission throughout the national grid system.

Three phase power is usually installed in larger properties including commercial and industrial properties. Some electrical equipment consumes larger amounts of energy, this can be achieved through increasing the voltage and a 3 phase supply achieves this through using multiple live wires adding their voltage to each other, the types of equipment that use 3 phase power to achieve this include the following:

  • Air conditioning
  • Heating
  • Motors and pumps
  • Heavy machinery
  • UPS systems

Electricity supplied to smaller and domestic properties is usually delivered via one live (phase) wire, this will supply power at around 230 volts (although this can be in excess of 240 volts and sometimes higher than 250 volts) this type of power requires a neutral conductor (wire) to work as it is assumed that electricity moves from wires that have higher voltages to wires that have lower voltages, and neutral conductors should always be at zero volts, allowing power to move through the circuits in your home

A three phase supply utilises three live wires, the voltage that exists between either two or all three of these live wires is 400 volts, this voltage used to be 415 volts but was reduced to 400 volts to harmonise with European standards. Three phase systems also typically employ a neutral wire. Because most electrical devices are single phase items and are rated at 230 volts, it is necessary to provide a neutral conductor for these items to function, this includes any device that plugs into a 13-amp socket outlet.

Phase balancing is an important consideration when installing a three phase system – this is where each of the phases have as near as possible, equal amounts of current flowing in the conductors. When phases are out of balance voltages can exist in the neutral conductor where the voltage should be at zero. Other issues that can be encountered when the phases are out of balance is that one conductor exceeds its capacity, causing the fuse to blow, while other conductors are well below the threshold to blow. Rearranging the loads to balance out the system can usually bring the system into harmony and remove the overloading issues.

Your supply company is likely to charge for the installation of three phase power, and this can run into many thousands of pounds, but once it is installed the price per unit is the same as that for single phase power, unless a lower price has been negotiated with the supply company. To arrange for a three phase power supply to be installed can take many months depending on local availability and other considerations determined by such factors as is it necessary to dig up the pavement or road, and how this will impact on the public, traffic flow and the movement of the emergency services.

An application form will need to be submitted, with a set of plans of the local area and another of the building into which the 3 phase supply will be brought into, its final position should be marked on these plans, which is usually local to the distribution system of the building. It must be taken into account that three phase consuming devices are usually items that require more power, which is why the power is spread over three separate conductors rather than just the one.

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