All synchronous generators are invariably _________.

Concept:

Star connected system:

• In the star connection, the similar ends (either start or finish) of the three windings are connected to a common point called star or neutral point.
• The three-line conductors run from the remaining three free terminals called line conductors.
• The wires are carried to the external circuit, giving three-phase three-wire star connected systems.
• Sometimes a fourth wire is carried from the star point to the external circuit, called neutral wire, forming three-phase four-wire star connected systems.

Delta connected system:

• It is formed by connecting one end of the winding to the starting end of other winding and the connections are continued to form a closed loop.
• It is always a three-phase three-wire system as the neutral wire is absent in this system.

The relation between phase and line quantities:

Let VL is the line voltage

Vph is the phase voltage

IL is the line current

Iph is the phase current

In a star connected system,

\({V_{ph}} = \frac{{{V_L}}}{{\sqrt 3 }}\)

IL = Iph

In a delta connected system,

\({I_{ph}} = \frac{{{I_L}}}{{\sqrt 3 }}\)

Vph = VL

Application:

The armature winding of the alternator or synchronous generators is generally connected in a star connection because of the following reasons:

1. The phase voltage is 0.577 times the line voltage which results in lesser voltage stress and hence lesser insulation cost.
2. The availability of the neutral point can be grounded and thus provide a path for circulating current in case there is any unbalance in the load end or some fault occurs.

3. Lesser turns of wire are required and Higher terminal voltage is obtained.