# Explain three phase generation of voltage ? electrical engineering

## Generation of three-phase voltages

Let three coils are placed in a uniform magnetic field. These coils arc placed 1200 apart as shown in the figure. If these coils are rotated at the same speed in the magnetic field, three voltages will be induced in the coils. These voltages will be 1200 apart in phase from each other e.g.

The order in which the voltages will reach the peak or maximum value is known as phase-sequence For the given voltage we say that phase order or phase sequence is 1 -2- 3.

If the direction of rotation of coils is reversed then the phase sequence will also change and would become  1 -3- 2 This sequence means 3 is 1200 behind 1 and 2 is 1200 behind 3. There are two general connections in three phase systems.

1) Star or Y connection and

2) Delta or mesh or  connection.

If the three coils arc placed such that they have one common terminal (known as neutral), then it is a star. or Y connection as shown in fig.

It is known as 3 phase, 4 wire star connected system. If three coils are placed such that they forms a close circuit, then it is known as delta or mesh connection. It is always a 3-phase, 3 wire system.