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Monday, 17 August 2015

Construction and Working Principle Transformer

Construction and Working Principle Transformer Points : Construction and Working Principle Transformer Working Principle Transformer is a fixed (or motionless) part of equipment through way of which electric power in one circuit is changed into electric power of the similar frequency in an additional circuit. It can increase or lower voltage in a circuit has by a equivalent reduced or enhance in current. The physical basis of a transformer is joint induction among two circuits coupled through a familiar magnetic flux. In its simplest structure, it consists of two inductive coils which are electrically divided but magnetically linked through a path of low reluctance. The two coils have high mutual inductance. If one coil is linked to a cause of alternating voltage, an alternating flux is set up in covered core, toast of which is connected by other coil in which it generate equally induced e.m.f. (according to Faraday’s Laws of Electromagnetic Induction e = MdI/dt). If second coil circuit is closed, a current flows in it and so electric energy is transfer (completely magnetically) from the rims coil to second coil. First coil, in which electric energy is fed as of the a.c. supply mains, is call primary winding and other from which power is drown out, is call secondary winding. In concise, a transformer is a device that
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)

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