1. transfers electric power front one circuit to any more
2. it does so with no o change of frequency
3. it realize this by electromagnetic induction and
4. where two electric circuits are in common inductive influence of each other. Construction The natural constituent of a transformer consists of two coils have joint inductance and a covered steel core. Two coils are insulating as of each other and steel core. Other required parts are: various proper container for assemble core and windings ; a right medium for insulate the core and its windings as of its container ; proper bushings (also of porcelain, oil—packed or capacitor—type) for insulate and bringing out terminals of windings as of tank. In every types of transformers, core is construct of transformer sheet steel laminations assemble to give a nonstop magnetic path by a minimum of air—gap included. Steel use is of high silicon substance, sometimes heat treated to create a high permeability anti a low hysteresis failure at the common operating flux densities. The eddy current loss is minimize with laminating core, the laminations being insulate as of each other through a light coat of core—plate varnish or through an oxide layer on surface. The widths of laminations vary as of 0.35 mm for a rate of 50 Hz to 0.5 mm for a frequency of 25 Hz. Core laminations (in the form of strips) are coupled as shown. It is seen that joints in the alternate layers are stagger in order to shun the existence narrow gaps right through cross-section of core. Such staggered joints are assumed to be ‘imbricated.
Constructional, transformers are of two common types, distinguished from each other only through the manner in which the primaries anti secondary coils are positioned about the laminated core. The two types are known as
1. Core type
2. Shell type (i) Core Type Transformer Core type transformer, windings are cylindrical former wound, mount on the core limbs. The cylindrical coils have dissimilar layers and each layer is insulating as of each other. Materials similar to paper, cloth or mica can be use for insulation. Low voltage windings are placed earlier to core, as they are easier to insulate. (ii) Shell Type Transformer Shell type transformer the coils are former wound and mount in layers stacked by insulation among them. A shell type transformer might have easy rectangular form or it can have a dispersed form.
(B) On the basis of their function
Step up transformer: Voltage increase (by subsequent decrease in current) at secondary.
Step down transformer: Voltage decrease (by subsequent increase in current) at secondary.
(C) On basis of type of supply
Single phase transformer
Three phase transformer
(D) On the basis of their use
Power transformer: Used in transmission network, elevated rating
Distribution transformer: Used in distribution network, moderately lower rating than that of power transformers.
Instrument transformer: Used in transmit and protection reason in different instruments in industries
Current transformer (CT)
Potential transformer (PT)
(E) On the basis of cool working
Oil-filled self cooled type
Oil-filled water cooled type
Air blast type (air cooled)