SOLUTION

A synchroscope is a device that produces a revolving field proportional to the speed difference between the incoming machine and the system. It is constructed so that the angular phase difference is indicated on the synchroscope dial.

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A synchroscope indicates when two AC generators are in the correct phase relation of connecting in parallel and shows whether the incoming generator is running faster or slower than the online generator.

A pointer is attached to the synchroscope rotor and rotates over a dial face.

• If the frequencies of the incoming and running generators are different, the synchroscope will rotate at a speed corresponding to the difference.
• A Synchroscope indicate the correct speed when the pointers move vertically up.
• It is designed so that if the incoming frequency is higher than the running frequency, it will rotate in the clockwise direction.
• If the incoming frequency is less than the running frequency, it will rotate in the counterclockwise direction.
• When the synchroscope indicates 0° phase difference, the pointer is at the ” 12 o’clock” position and the two AC generators are in phase. When the pointer stops in a vertically upward position, the frequencies are equal and the voltages are in phase. This means that the alternators are in synchronism and the alternator switch can be closed to parallel both machines.