Test: Transformer Construction
10 Questions MCQ Test Electrical Machines | Test: Transformer Construction
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The primary and secondary of a transformer are ________ coupled but _______ connected.
- 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 has comparitively much higher efficiency than a similar induction machine due to
- 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.
It was needed that to isolate dc noise coming from the transmitted signal, to attain the same which machine can be used without suffering significant loss
We should use transformer to achive the isolation of dc.
The most widely used material in the core of the transformer is
CRGO (Cold rolled gain oriented) has magnetization in the rolling direction and low core losses and very high permeability than present materials.
The leakage flux is the flux inside the transformer which
- 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.
Consider two transformers A and B having exact ratings, but have flux densities of 1.5T and 2T respectively. The weight of transformer A per KVA will be
Flux density = flux/Area.
Hence A has more area than B and so weight of A will be more than that of B.
A coupling magnetic field inside a rotating machine or static machine like transformers must involve with
The coupling field should interact with both the electrical as well as mechanical parts in order to achieve electromechanical energy conversion.
A coupling magnetic field inside a rotating machine or static machine like transformers must involve with:
I. electrical system to extract energy from electrical system.
II. mechanical system to extract energy from electrical system.
The energy conversion which involves both electrical as well as mechanical systems must have mutual field.
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