Question 571. 7. 1n the protection of transformers, harmonic restraint is used to guard against

Question 572. 8. The main reason for connecting a pulse transformer at the output stage of a thyristor triggering circuit is to

Question 573. 0.  A lkVA, 230 V/100V, single phase, 50 Hz transformer having negligible winding resistance and leakage inductance is operating under saturation, while 250 V, 50 Hz sinusoidal supply is connected to the high voltage winding. A resistive load is connected to the low voltage winding which draws rated current. Which one of the following quantities will not be sinusoidal?

Question 574. 1.  A 400V/200V/200V, 50Hz three winding transformer is connected as shown in Fig. 8.1. The reading ofthe voltmeter, V,will be400V 50 Hz

Question 575. 4.  The equivalent circuit of a transformer has leakage reactances X1, X'2 and magnetizing reactance Xm. Their magnitudes satisfy

Question 576. 3.  A 500 kVA, 3-phase transformer has iron losses of 300 W and full load copper losses of 600 W. The percentage load at which the transformer isexpected to have maximum efficiency is

Question 577. 5.  Which three-phase connection can be used in a transformer to introduce a phase difference of 30? between its out put and corresponding input time voltages

Question 578. 2.  A single phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is

Question 579. 6.  A bank of three identical single-phase 250 kVA, 11 kV/230 V transformers is used to provide 400 V low tension supply from a 11 kV, 3-phase sub-station. The effective kVA rating of the bank will be

Question 580. 7. .A 4 kVA, 230/115 volt, 400 Hz, single-phase transformer, originally designed for use in aircrafts, isavailable in a laboratory for obtaining 115 V supply from standard 230 V, 50 Hz mains.If overloading ofthe device is not permitted, thenthe net kVA output of the transformer in the laboratory cannot exceed