Electrical Machines Objective Questions – Set 14

In a transformer

Silicon content in steel lamination is kept within 5% as it

Transformer oil is used as

If P_i and P_c represent core and full load copper loss respectively, the maximum KVA delivered to load corresponding to maximum efficiency is equal to rated KVA is

In a single phase transformer the magnitude of leakage reactance is twice that of resistance of both primary and secondary. With secondary short circuited, the input power factor is

A transformer core is made up of a silicon steel laminations which has maximum flux density 1 Tesla. If it was cold rolled grain oriented its flux density increases to 1.6 Tesla. What is the saving in core size or area due to cold rolled grain oriented process?

In a transformer, hysteresis and eddy current losses depend upon

A 100 KVA transformer is operating at 60 Hz, 240 V supply. The same transformer is operating at 50 Hz, 200 V supply. The new rating is

Open circuit test on transformer gives

If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

Open circuit in a transformer is prefered with

A transformer has resistance and reactance in per unit as 0.01 and 0.04 respectively. Its voltage regulation for 0.8 power factor lagging and leading will be

In a transformer zero voltage regulation is achieved at a load power factor which is

Conservator tank is used

Transformer core is laminated to reduce

A shell type transformer has

1 KVA, 230 V, 50 Hz, single phase transformer has an eddy current loss of 30 watts. The eddy current loss when the transformer is excited by a dc source of same voltage will be

Which of the following statements is/are correct statements?

For a transformer to be tested at full load conditions but consuming only losses from the main, we do

The use of higher flux density in the transformer design

When a short circuit test on a transformer is performed at 25 V, 50 Hz, the drawn current is I₁. If the test is performed by 25 V and 25 Hz and power drawn current is I₂, then

The full load copper loss and iron loss of transformer are 6400W and 5000W respectively. The copper loss and iron loss at half load will be respectively?

The constant losses in transformer is/are

In a transformer operating at constant voltage if the input frequency increases, the core loss

Which is the arrangement of windings in a core type single phase transformer?

A 2 KVA transformer has iron loss of 150 W and full load copper loss of 250 W. The maximum efficiency of the transformer would occur when the total loss is

A transformer has maximum efficiency at 3/4 load. The ratio of iron loos and full load copper loss is

stepped cores are used in transformers in order to reduce

A single phase transformer when supplied from 220 V, 50 Hz has eddy current loss of 50 W. If the transformer is connected voltage of 330 V, 75 Hz, the eddy current loss will be

A transformer has hysteresis loss of 30 W, at 240 V, 60 Hz. The hysteresis loss at 200 V, 50 Hz will be