TRANSFORMER:

WORKING PRINICIPLE OF TRANSFORMER:

A transformer is a device that

1. Transfers electric power from one circuit to another

2. It does so without a change of frequency

3. It accomplishes this by electromagnetic induction

4. Where the two electric circuits are in mutual inductive influence of each other.

Constructionally, the transformers are of two general types,

1. Core-Type

2. Shell-Type. Another recent development is spiral-core or wound-core types the trade name being spirakore transformer. The spiral-core transformer employs the newest development in core construction. The advantages of such construction are

1. A relatively more rigid core

2. Lesser weight and size per kVA rating

3. Lower iron losses at higher operating flux densities

4. Lower cost of manufacture.

Transformers are generally housed in tightly-fitted sheet-metal tanks filled with special insulating oil*. This oil has been highly developed and its function is two-fold. By circulation, it not only keeps the coils reasonably cool, but also provides the transformer with additional insulation not obtainable when the transformer is left in the air.

Classifying the transformers is according to the type of cooling employed. The following types are in common use:-

1. Oil-filled self-cooled

2. Oil-filled water-cooled

3. Air-blast type.

IDEAL TRANSFORMER:

An ideal Transformer is one which has no losses i.e. its windings have no ohmic resistance, there is no magnetic leakage and hence which has no I²R and core losses. In other words, an ideal transformer consists of two purely inductive coils wound on a loss-free core.