What is electric phases.?

Answer 1

A quick lesson on three-phase a.c. terminology.

The three energised ('hot') conductors that connect the load to the supply are termed 'lines' or 'line conductors'. The fourth wire, if present, is called the 'neutral' or 'neutral conductor'.

Anything connected between individual lines, in a three-phase, three-wire, system, are called 'phases'; anything connected between a line and neutral, in a three-phase, four-wire system, are called 'phases'.

So the individual windings of a three-phase alternator or three-phase transformer are phases. The three individual impedances that make up a three-phase load are also phases. The wires that connect the supply to the load are lines.

Voltages measured between lines, and the currents through lines, are called 'line voltages' and 'line currents', respectively. Voltages measured across individual loads, and the currents through those loads, are called 'phase voltages' and 'phase currents', respectively.

(Ignore anyone who calls the conductors that join the supply to the load, 'phases'. This is quite common but completely wrong!)

Answer 2

Phasing is distinguishing the conductor voltage characterstics and magnitude with respect to other conductors.

Phase neutral..

Phase at a definite potential and neutral at zero.

In three phase

All three phases are at same voltage but are 120° apart from other in their cycles. Its an engineering thing to understand.

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Phasing describes the exact moment that a sine-wave starts from zero. In 3-phase systems there are three live wires, and each one is 'phased' one third of a cycle, or 120°, apart. In a 50 Hz system the full cycle is 20 milliseconds so the three sine-waves peak in regular succession, 20/3 milliseconds apart.

Why this is important is that at every instant the sum of the three currents is zero in a balanced three-phase system. So if the three neutral wires are connected together, there is no current in the common neutral and it is not needed. It can be dispensed with, which saves half the wire. So 3-phase power can be transmitted with three live wires and no neutral because the current in each live wire is returned through the other two.

In some cases the currents are not balanced and a neutral is required, which is a 3-phase 4-wire system, common in low-voltage power distribution below 500 v.