Application of Synchroscopes

Application of Synchroscopes Points : Application of Synchroscopes, Uses of Synchroscopes Before connecting an incoming alternator to a bus-bar, the following conditions must be fulfilled:
(a) Their terminal voltage must be equal.
(b) Their voltages must be in phase
(c) Their frequency must be equal
(d) Their phase sequence must be same

When the two alternators are operating so that these conditions are satisfied, they are said to be in synchronism. The Operation of getting the machines in to synchronism can be done by synchronising. Synchronising can be done “Synchronising lamp method”. This method can not be employed in case of large power stations where the generated voltage is very high. In such cases synchroscope is used. Synchroscope is a single phase device and provides a more accurate indication of synchronism than lamps.

The synchroscope is an instrument for indicating differences of phases and frequency between two voltages. It is essentially a split phases motor in which torque is developed if the two voltages applied differ in frequency. Voltages from corresponding phases of the incoming and running generators are applied to the synchroscope. A pointer, which is attached to the rotor of the instrument, moves over the dial in either a clockwise direction or counter-clockwise direction, depending on whether the incoming generator is fast or slow. The dial marking of a synchroscope is shown.

When the pointer stops, the frequency of the two generators are same. When the pointer stops in the vertical position, the frequencies are same, the voltages are in phase, then the paralleling switch may be closed.