3-Phase supply, Earthing wire & Neutral wire

Explain terms:   1.   3phase supply

                        2.   Earthing wire

                        3.   Neutral wire

ANS:

1. Three phase electric supply:

          In a normal single-phase line, there will be two wires.  One is called as live wire or phase wire and the other is called as neutral wire.  Voltage is available at live wire only.  Neutral wire is used for completing the loop.  In a three-phase line, there are three live wires and one neutral wire. [For star connection only].

          The generator or alternator generates the electric current. In the electric generator, if one coil is rotated in the magnetic field, single phase or single supply of electric current will be generated.  Whereas, if three coils separated 120° apart, are rotated; three separate supplies of electric currents are generated.  Such kind of supply is called a three-phase supply. As a convention, for three phases, three basic colours, that is, Red, Yellow and blue wires are used. For neutral wire black colour is used.

2. Earthing wire:

               In addition to phase wires and neutral wires there is one more wire  [normally green] called earthing wire.  This wire connects the device-body to the earth.  This connection enables a large quantity of the leakage current to pass through this wire to the earth. And a very small amount of current passes through the human body to the earth. Thus, the human beings are saved from the shock effects.  

 3. Neutral wire:

In an alternative current for a single-phase supply, these are two wires. One is called as phase wire and other is called as neutral wire. Electric supply is given to the phase wire and the neutral wire just completes the circuit. The on- off switch is installed in phase wire. The neutral wire is normally black in colour.