To connect the 2 generators with the 1 existing working generators, first we have to bring the speed of the prime mover of the 2nd generator to the rated speed. At this point switch S4 is closed.
The circuit breaker V2 (voltmeter) connected across the open switch S2 is closed to complete the circuit. The excitation of the generator 2 is increased with the help of field rheostat till it generates voltage equal to the voltage of bus-bars.
The main switch S2 is then closed and the generator 2 is ready to be paralleled with existing generator. But at this point of time generator 2 is not taking any load as its induced e.m.f. is equal to bus-bar voltage. The present condition is called floating, that means ready for supply but not supplying current to the load.
In order to deliver current from generator 2, it is necessary that its induced e.m.f. E should be greater than the bus-bars voltage V. By strengthening the field current, the induced e.m.f. of generator 2 could be improved and the current supply will get started. To maintain bus-bar voltage, the field of generator 1 is weakened so that value remains constant.
Field current I given by
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