A star-connected 440V, the 50Hz alternator has per phase synchronous reactance of 10?. It supplies a balanced load current of 20A, as shown in the per-phase equivalent circuit diagram below. It is desirable to have a zero voltage regulation. The load power factor should be

Question

RRB Paper · Accepted Answer

To achieve zero voltage regulation, the synchronous reactance of the alternator must be balanced by an equal and opposite reactance in the load.

Vph = Vload

cos(φ) = Re(Zload) / |Zload|

The voltage drop across the synchronous reactance of the alternator is:

Vx = jXs * I

where:

Xs = synchronous reactance of the alternator

The voltage drop across the load impedance is:

Vload = Zload * I

Since Vph = Vload

Vx = Zload * I - Vph

Substituting the values

The load impedance has a phase angle of:

φ = atan(10 / 22) = 23.4°

Therefore, the load power factor is:

cos(23.4°) = 0.92

A star-connected 440V, the 50Hz alternator has per phase synchronous reactance of 10?. It supplies a balanced load current of 20A, as shown in the per-phase equivalent circuit diagram below. It is desirable to have a zero voltage regulation. The load power factor should be

0.82

0.62

0.50

0.92

The correct answer is `No. 4: 0.92`

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A star-connected 440V, the 50Hz alternator has per phase synchronous reactance of 10?. It supplies a balanced load current of 20A, as shown in the per-phase equivalent circuit diagram below. It is desirable to have a zero voltage regulation. The load power factor should be

0.82

0.62

0.50

0.92

The correct answer is No. 4: 0.92

The correct answer is `No. 4: 0.92`