Different Types of the transformer

A transformer is a static electrical device which transfer a.c. electric power from one circuit to another circuit at the same frequency.

From this definition,we can conclude that

Transformer is a static electric device and do not have any rotating parts.
It change electrical power starting with one circuit then onto the next circuit at a similar frequency at various voltage.
It operate only with alternating current and do not function with D.C.supply.

there are two types of transformer:

1. core type transformer

2. shell type transformer

1. core type transformer:

core type transformer

In the core-type transformer,the magnetic circuit consists of two vertical sections called limbs with two horizontal sections, called yokes.
The primary and secondary winding are provided on each limb.
The low voltage winding is kept inside near the core,while the high voltage winding is placed on it.
This type of winding arrangement in the core type transformer provides magnetic coupling between primary and secondary winding.
Thus,the two windings are arranged as concentric coils such a windings is therefore,called concentric winding.
in most of the core type transformers circular cylindrical coils are used because of their mechanical strength , while placing these coils an insulation layer is provided between core and lower coil and also between the two coils.
it should be noted that low voltage winding is wound near the core since it is easiest to insulate.if the high voltage winding is wound near the core a heavy insulation will have to be prvided to avoid earth leakage.

core type transformer

advantages :

2. shell- Type transformer :

shell- Type transformer

in the shell- type transformer both primary and secondary winding are wound on the central limb and the two outer limbs complete the low reluctance flux paths.
winding are normally of sandwich type.
the top and bottom coils, which are near the yoke of the core, are of L.V. winding only.

advantages :

disadvantages :

Distribution transformer :

distribution transformer

Transformer upto 500 kVA are used to step down distribution voltage to a standard service voltage or from transmission voltage to distribution voltage are known as distribution transformers.
They are kept running all 24 hours a day, regardless of whether or not they carry loads. The load on the distribution transformer varies from time to time and the transformer will remain empty for most of the time.
Therefore in the distribution transformer the loss of copper (which depends on the load) will be greater than the loss of the core (which occurs until the transformer is in operation).
So the distribution transformers are designed with less iron loss and designed to have maximum efficiency at a much lower load than full load.
it should have a good regulation to maintain the variation of the supply voltage with limits and therefore it is designed with a reduced value of the dispersion reactance.

power transformer :

power transformer

The transformers used in sub-stations and generating stations are called power transformers.
They have ratings above 500 kVA.Usually a substation will have number of transformers working in parallel.
During heavy load periods all the transformers are put in operation and during light load periods some transformers are disconnected.
The power transformer is designed to have a leakage response greater than the permissibility in the distribution transformer to limit the fault fault.
In the case of power transformers, inherent voltage regulation is less important than the current limiting effect of high leakage response.