Ans : A transformer is a static piece of apparatus which transforms electrical energy from one Circuit to another circuit without changing the frequency either stepping up or stepping down the voltage .

Ans : The principle of operation of a transformer is based upon the theory of mutual induction Between two electrical linked by a common magnetic flux .

Ans: The rating of a transformer is the maximum power which can be drawn from it without the temperature rise in the winding exceeding the safe limits for the particular class of insulation employed .

Ans: The rated capacity of a transformer is expressed in KVA not in KW. Generally the rating of a transformer is determined by its temperature rise . The temperature rise is caused by the losses in the machine . Copper loss depends on the value of the load current and iron loss on voltage . Therefore ,total loss of a transformer depends on volt-ampere (VA) and is independent of load power Factor. A certain amount of current will produce the same I² R loss at any value of power factor . This loss limits the output of the machine .The output in kilowatts is proportional to the power factor . For a given KW load if the power factor decreases, the load current increases proportionately causing more losses and temperature rise in the machine . For the above reason, transformers are generally rated in KVA, not in KW .

Ans : The power factor of a transformer is very low and lagging on no load . But the power factor on load is nearly equal to the power factor of the load which it is carrying .

Ans :The no load current in a transformer normally lags behind the voltage by about 7⁰.

Ans: The essential parts are as follows :- a)Magnetic circuit consisting of laminated iron core and clamping structures. b)Primary winding . c)Secondary winding . d)Tank filled with insulating oil . e)H.T terminals with bushing . f)L.T terminals with bushing . g)Conservator tank. h)Breather. i)Vent pipe . j)WTI ( Winding Temperature Indicator ) & OTI ( Oil Temperature Indicator). k)Radiator.

Ans : Primary winding .

Ans: Secondary winding .

Ans: Lamination of specially alloyed silicon steel (silicon content 4 to 5%) are used due to its high electrical resistance ,high permeability non-ageing characteristics and minimum iron loss .

Ans :The iron core is used in a transformer to provide a continuous easy magnetic path of low reluctance .

Ans: The magnetic leakage is reduced to a minimum by sectionalizing & interleaving the primary and secondary windings .

Ans: The joints in iron core should be staggered to avoid clear air gap in the magnetic circuit as the air gap reduces the magnetic flux due to its high reluctance .

Ans: Iron cores are made laminated to reduce the eddy current loss .

Ans: Frequency.

Ans: The laminations are insulated from each other by insulating varnish or thin paper to break the path of eddy currents thus to reduce the eddy current loss .

Ans: Stacking factor is the ratio of iron content in the laminated varnished core by volume. Its value is about 90% i.e. 10% volume is occupied by the varnish and air .

Ans: The grain oriented laminations are such cold rolled laminations specially annealed to orient the iron crystals i.e the grains in a uniform direction in the direction of rolling which produces loss . These laminations are punched and assembled in such a way that the grains of different lamina line in the same direction as the magnetic field and not across it .

Ans: 1.6 to 1.8 weber per meter .

Ans : To make it free from vibration and humming sound.

1. Transformer’s interview questions paper-2
2. Transformer interview questions paper-1
3. Transformer’s interview questions paper-3
4. Transformer interview questions paper-4
5. Transformer interview questions paper-5
6. Core type Transformer and Shell type Transformer
7. Transformer interview questions paper-6
8. Transformer’s interview questions paper-7
9. Interview questions of Transformer paper-8
10. Interview questions of Transformer paper-9
11. Interview questions of Transformer paper-10
12. Transformer interview Questions & Answers paper-11
13. Transformer interview Questions & Answers paper-12
14. Transformer interview Questions & Answers paper-13