BASIC CONCEPTS AND CONSTRUCTION FEATURES OF TRANSFORMER
A transformer is a device that makes use of Faraday’s law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages. It of course cannot increase power so that if the voltage is raised, the current is proportionally lowered and vice versa. A transformer is a static electrical device that transfers energy by inductive coupling between its winding circuits. A varying current in the primary winding creates a varying magnetic flux in the transformers’ core and thus a varying magnetic flux through the secondary winding.
Transformers range in size from thumbnail-sized used in microphones to units hundreds of tones interconnecting the power grid.
for the simple construction of a transformer, you must need two coils having mutual inductance and a laminated steel core. The two coils having mutual inductance and a laminated steel core. The two coils are insulated from each other and from the steel core. The device will also need some suitable container for the assembled core and windings, a medium with which the core and its windings from its container can be insulted.
In order to insulate and to bring n be done with the help of a light oatout the terminals of the terminals of the windings from the tank, apt bushings that are made from either porcelain or capacitor type must be used.
In all transformers that are used commercially, the core is made out of transformers sheet steel laminations assembled to provide a continuous magnetic path with minimum of air-gaped included. The steel should have high permeability and low hysteresisi loss. For this to happen the stell should be made of high silicon content and must also be heat traeted. By effectively laminating the core , the eddy-current losses can be reduced. The lamination can be done with the help of a light coat of core plate vamish or lay an oxide layer on the surface. For a frequency of 50 hetz , the thickness of the lamination varies from 0.35mm to 0.5mm for frequency of 25 hertz.
These were the basic concepts and construction features of transforemers.
SOME EXPECTED QUESTIONS BASED ON TRANSFORMERS ARE:
ques 1)what are taps and when they are used?
ans- taps are provided on some transformers on the high voltage winding to correct for high or low voltage conditions, and still deliver full rated output voltages at the secondary terminals.Standard tap arrangements are at two and one half and five percent of the rated primary voltage for both high and low voltage conditions.
ques 2) can a transformer develop three phase power from a single phase source?
ans- NO.. Phase converters or phase shifting devices such as reactors and capacitors are required to convert single phase power to three phase.
ques 3) What is meant by regulation in a transformer?
ans- Voltage regulation in transformers is the difference between the no load voltage and full load voltage. This is usually expressed in terms of percentage.
ques 4) What is meant by impedance transformers?
ans- Impedance is the current limiting characteristics of a transformer and is expressed in percentage.
ques 5) What colour are ACME Dry Type transformers?
ans- ASA 61(NEMA) light gray is used on all enclosed transformers from 50 to 500 KVA