Synchroscope:
A synchroscope denotes while two AC generators are in the correct phase relation for linked in parallel and displays whether the incoming generator is running faster or slower than the on-line generator. A synchroscope consists of a two-phase stator. The two stator windings are at right angles to one another, and through means of a phase-splitting network, a current in one phase leads the current of the other phase through 90°, thus producing a rotating magnetic field. The stator windings are linked to the incoming generator and a polarizing coil is linked to the running generator.
The rotating element is unrestrained and is free to rotate by 360°. That consists of two iron vanes mounted in opposite directions on a shaft, one at the top and one at the bottom, and magnetized through the polarizing coil.
The synchroscope will rotate at a speed corresponding to the difference if the frequencies of the incoming and running generators are different. It is designed so in which if incoming frequency is higher than running frequency, it will rotate in the clockwise direction; if incoming frequency is less than running frequency, it will rotate in the counterclockwise direction. While the synchroscope denotes 0o phase difference, the pointer is at the "12 o'clock" position and the two AC generators are within phase.