WHAT IS A TRANSFORMER?
TRANSFORMER IS A STATIC DEVICE WHICH
TRANSFERS AN ELECTRICAL POWER FROM ONE ELECTRICAL CIRCUIT TO ANOTHER ELECTRICAL
CIRCUIT OR MULTIPLE CIRCUITS. IT IS A STATIC OR STATIONARY DEVICE BECAUSE IT
DOES NOT CONTAIN ANY MOVING PART LIKE ELECTRICAL MOTORS.
PRINCIPLE OF TRANSFORMER -
TRANSFORMER IS A DEVICE WHICH IS CAPABLE OF
CONVERTING AC VOLTAGES AND CURRENT OF HIGH VALUE INTO LOW OR DESIRED VALUE AND TRANSFERS
IT TO THE REQUIRED LOCATION FOR UTILIZATION PURPOSE. ELECTRICAL TRANSFORMER
PLAYS AN IMPORTANT ROLE IN ELECTRICAL POWER SYSTEM.
TRANSFORMER WORKS ON THE PRINCIPLE OF MUTUAL INDUCTION. IN TRANSFORMER THERE ARE TWO COILS PLACED USING SAME CORE BUT ON DIFFERENT LIMBS, ONE IS PRIMARY COIL AND OTHER IS SECONDARY COIL. THIS CREATES A MAGNETIC CIRCUIT FOR BOTH COILS. THESE COILS ARE HAVING HIGH MUTUAL INDUCTANCE, WHEN AN ELECTRICAL CURRENT PASSES THROUGH THE PRIMARY COIL IT PRODUCES MAGNETIC FIELD AROUND IT, WHICH WILL PASS THROUGH THE TRANSFORMER CORE AND LINKS WITH THE SECONDARY COIL. THE MAGNETIC FIELD OR FLUX IS ALTERNATING IN NATURE THUS, ACCORDING TH FARADAY'S LAW OF ELECTROMAGNETIC INDUCTION AN EMF (ELECTROMOTIVE FORCE) WILL BE INDUCED IN THE SECONDARY COIL AND CURRENT WILL START FLOWING THROUGH IF LOAD IS CONNECTED. THIS PHENOMENA IS CALLED MUTUAL INDUCTION.
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| SINGLE PHASE TRANSFORMER |
THE TRANSFORMER INCREASES OR DECREASES THE
VOLTAGE LEVEL DEPENDS ON THE RELATIVE NUMBER OF TURNS BETWEEN THE PRIMARY AND
SECONDARY SIDE OF THE TRANSFORMER.
A TRANSFORMER THAT INCREASES VOLTAGE BETWEEN THE PRIMARY TO SECONDARY WINDINGS IS CALLED AS A STEP-UP TRANSFORMER. FOR STEP UP TRANSFORMER THE NUMBER OF TURNS ON PRIMARY COIL IS LESS THAN SECONDARY COIL THUS THE VOLTAGE WILL INCREASE.
A TRANSFORMER THAT DECREASES VOLTAGE BETWEEN THE PRIMARY TO SECONDARY WINDINGS IS CALLED AS A STEP-DOWN TRANSFORMER. FOR STEP DOWN TRANSFORMER THE NUMBER OF TURNS ON PRIMARY COIL IS MORE THAN SECONDARY COIL THUS THE VOLTAGE WILL DECREASE.
[NOTE = THERE IS A DIFFERENCE BETWEEN INDUCTION AND PRODUCTION. WE ARE INDUCING AN EMF FROM MAGNETIC FIELD LINES THUS WE CALL IT AS "INDUCTION OF EMF IN SECONDARY WINDING". IT IS NOT THE MAGNETIC LINES THAT SUPPOSED TO PRODUCE EMF, WE ARRANGED THE CIRCUITRY IN SUCH A WAY THAT MAGNETIC LINES ARE SET IN THE CORE AND WILL BE LINKED WITH SECONDARY WINDING TO INDUCE EMF IN IT.]
MAJOR PARTS OF TRANSFORMER –
- TRANSFORMER WINDINGS – THERE ARE TWO WINDINGS IN TRANSFORMER PRIMARY AND SECONDARY. PRIMARY WINDING IS THE ONE WHICH CARRIES THE CURRENT FROM SOURCE AND SECONDARY WINDING IS THE ONE WHO TRANSFERS THE CURRENT TO LOAD. WINDINGS ARE MADE UP OF COPPER WHICH HAS HIGH CONDUCTIVITY AND HIGH DUCTILITY PROPERTY. WINDINGS ARE INSULATED WITH VARNISH.
- MAGNETIC CORE – CORE IS MAJOR PART IN TRANSFORMER IT DOES MULTIPLE JOBS OF HOLDING OR SUPPORTING THE TRANSFORMER WINDINGS AND PROVIDING LOW RELUCTANCE PATH TO THE MAGNETIC FLUX LINES. CORE IS MADE UP OF LAMINATED SILICON STEEL STAMPING TO PROVIDE HIGH PERMEABILITY AND REDUCE THE CORE/IRON LOSSES IN TRANSFORMER.
- INSULATION FOR CORE AND WINDINGS – INSULATION IS IMPORTANT FOR WINDINGS TO PREVENT THEM FROM CAUSING SHORT CIRCUIT. INSULATION IS ALSO IMPORTANT AT TERMINALS TO PREVENT THEM FROM CORROSION AND ANY DIRECT CONTACT WITH EACH OTHER. FOR SMALL TRANSFORMER INSULATION PAPER, INSULATION TAPE, VARNISH, LAMINATION, INSULATION OIL IS MOSTLY USED AS INSULATION MEDIA.
VOLTAGE TRANSFORMER RATIO –
(E1/N1)
= (E2/N2) = K
WHERE, K IS VOLTAGE TRANSFORMER RATIO AND IT IS CONSTANT,
E1 IS PRIMARY VOLTAGE,
E2
IS SECONDARY VOLTAGE,
N1 IS NO. OF PRIMARY WINDING TURNS,
N2 IS NO. OF SECONDARY WINDING TURNS.
IF, N2 > N1, THEN K > 1 FOR STEP-UP TRANSFORMER,
IF, N2 < N1, THEN K < 1 FOR STEP-DOWN TRANSFORMER.
