Construction & Working of Moving-Iron Synchroscope

Construction & Working of Moving-Iron Synchroscope Points : Construction and Working of Moving-Iron Synchroscope Its construction is similar to a single phase moving-iron power factor meter. It has got two iron pieces mounted one above the other separated by a brass piece on a common spindle

The fixed coil “CC” is connected across the bus bar. The two pressure coils are connected across the terminals of the incoming alternator. One of the pressure coils is connected in series with a non-inductive resistance “R” while the other is connected in series with an inductive coil of inductance “L’. When the frequency of the incoming machine is equal to that of bus bar, the synchroscope works as a single phase power factor meter and so indicates the phase difference between the two emfs.

When the frequency of the incoming machine is difference from the frequency of bus bar, the spindle rotates continuously at a speed in revolutions per second equal to difference between the frequencies of the two systems. The direction of rotation depends upon whether the incoming machine is running too fast or too slow.

The instrument has 3600 scale. The displacement from the zero position induces the phase difference between the emfs. When the pointer is stationary at the centre zero position. the paralleling switch should be closed.