Wednesday 5 August 2020

What is a 3-phase AC circuit?

A 3 phase AC circuit is a circuit or installation connected to a 3 phase supply. A 3 phase supply uses 3 active lines that may or may not need a neutral wire. A balanced 3 phase load like a 3 phase motor does not need a neutral. Each phase voltage is displaced by 120 degrees. This is due to the cool arrangement in the generator. 3 phases being the most economical arrangement of windings to produce a reasonable smooth load and a a reasonably smooth power source for a motor. On the left side is the 3 phase generators.

Below is a pictorial representation of the 3 phase voltages and winding inside a large generator.

Each phase is also referenced to neutral. So in a 400 volt 3 phase system the voltage between each phase is 400 volts and 230 volts between each phase to neutral. typical application is for a 3 phase motor or a machine that has a high load or several 3phase motors in the machine.

Most factories have a 3 phase supply because they have a high maximum demand ( or a high anticipated load) or have 3 phase motors.

Below is a typical 3 phase motor and circuit.

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