Test: Transformer Construction - Electrical Engineering (EE) MCQ

• Transformer is an electrostatic device, which consists of two are more electric circuits (or) windings, these windings are separated electrically but interlinked magnetically by a common magnetic core.
• Transformer is used to transfer electrical energy from one alternating-current circuit to another through the common magnetic core at the same frequency.

A transformer can be put in use upto a varying range of the power and it is usually available in readily in market.

The power rating of a transformer is obtained by simply multiplying the current by the voltage to obtain a rating in Volt-amperes, ( VA ).

Small single-phase transformers may be rated in volt-amperes only, but much larger power transformers are rated in units of Kilo volt-amperes, and units of Mega volt-amperes ( MVA )

• A transformer efficiency is always higher than the induction motor efficiency because there is no moving parts in a transformer, whereas mechanical losses occurs in an induction motor as it is not static machine like a transformer.
• Also, transformer has small air gap and strong coupling in comparison to induction motor.

We should use transformer to achive the isolation of dc.

CRGO (Cold rolled gain oriented) has magnetization in the rolling direction and low core losses and very high permeability than present materials.

• When the a.c power supply is applied to the primary winding of a transformer, the primary winding produces magnetic flux ϕ which flows through the iron core of the transformer, and magnetic flux cuts the secondary winding of the transformer.
• But, all the flux of primary winding does not cut the secondary winding. Some parts of the flux i.e. ϕ flow in the magnetic circuit by passing through the air rather than around the core (because air is not a good magnetic insulator).

Leakage flux is meant to be loss as it does not link two windings.

Staggering is done for the steel butt joints of the transformer to gain more mechanical strength as the continuous air gap reduces the same.

Flux density = flux/Area.
Hence A has more area than B and so weight of A will be more than that of B.

The coupling field should interact with both the electrical as well as mechanical parts in order to achieve electromechanical energy conversion.

The energy conversion which involves both electrical as well as mechanical systems must have mutual field.