HASMUKH GOSWAMI COLLEGE OF ENGINEERING TOPIC :- Transformer PREPARED BY, Guided by, Radadiya Radhika L. 140240109506 Niketan Dobriya Champaneri Shubham R.150243109501 Patel Jaimin S. 150243109014 Shrimali Chirag J. 150243109502 Tripathi Aman N. 150243109021 Electrical DEPARTMENT

Transformers A transformer is a device for increasing or decreasing an a.c. voltage.

WHAT IS A TRANSFORMER? TRANSFORMER IS A STATIC DEVICE WHICH TRANSFORMS A.C. ELECTRICAL POWER FROM ONE VOLTAGE TO ANOTHER VOLTAGE KEEPING THE FREQUENCY SAME BY ELECTROMAGNETIC INDUCTION.

TYPES OF TRANSFORMER BY APPLICATION 1. DISTRIBUTION TRANSFORMER 2.POWER TRANSFORMER 3.CURRENT TRANSFORMER 4.POTENTIAL TRANSFORMER 5.FURNACE TRANSFORMER 6.BOOSTER TRANSFORMER 7.RECTIFIER TRANSFORMER 8.LOCOMOTIVE TRANSFORMER 9.MINING TRANSFORMER 10.PHASE SHIFTING TRANSFORMER 11.WELDING TRANSFORMER 12.HIGH VOLTAGE TESTING/SC TESTING TRF. 13.GROUNDING TRANSFORMERS 14.CONVERTER TRANSFORMER

Structure of Transformer

PARTS OF TRANSFORMER MAIN TANK RADIATORS CONSERVATOR EXPLOSION VENT LIFTING LUGS AIR RELEASE PLUG OIL LEVEL INDICATOR TAP CHANGER WHEELS HV/LV BUSHINGS FILTER VALVES OIL FILLING PLUG DRAIN PLUG CABLE BOX

Circuit Symbol for Transformer

How Transformer works Laminated soft iron core Output voltage (a.c.) Input voltage (a.c.) Primary coil Secondary coil

Laminated iron core – this links the two coils magnetically. All transformers have three parts: Primary coil – the incoming voltage Vp (voltage across primary coil) is connected across this coil. Secondary coil – this provides the output voltage Vs (voltage across the secondary coil) to the external circuit. Laminated iron core – this links the two coils magnetically. Notice that there is no electrical connection between the two coils, which are constructed using insulated wire.

Two Types of Transformer A step-up transformer increases the voltage - there are more turns on the secondary than on the primary. A step-down transformer decreases the voltage - there are fewer turns on the secondary than on the primary. To step up the voltage by a factor of 10, there must be 10 times as many turns on the secondary coil as on the primary. The turns ratio tells us the factor by which the voltage will be changed.

Formula for Transformer Where Vp = primary voltage Vs = secondary voltage Np= Number of turns in primary coil Ns = Number of turns in a secondary coil.

Ideal Transformer Relationships Note that I2 and I2’ are in opposite directions

Worked example No. 1 The diagram shows a transformer Worked example No. 1 The diagram shows a transformer. Calculate the voltage across the secondary coil of this transformer. Step-up transformer!

Solution

Worked example No. 2 A transformer which has 1380 turns in its primary coil is to be used to convert the mains voltage of 230 V to operate a 6 V bulb. How many turns should the secondary coil of this transformer have? VP = 230 V NP = 1380 VS = 6 V NS = ? Obviously, a Step-down transformer!!

Solution

MAIN FEATURES OUTDOOR,OIL COOLED, 3 PHASE,50HZ PRIMARY IS DELTA CONNECTED AND SECONDARY IS STAR CONNECTED. NATURALY COOLED (ONAN TYPE). AMONGST ALL THE TYPES OF TRANSFORMERS THIS IS THE MOST REQUIRED AND MOST USED TYPE.

MAINTENANCE OF TRANSFORMER Transformer is the heart of any power system. Hence preventive maintenance is always cost effective and time saving. Any failure to the transformer can extremely affect the whole functioning of the organization.

PROTECTION OF TRANSFORMERS The best way of protecting a transformer is to have good preventive maintenance schedule. Oil Temperature Indicators. Winding Temperature indicators. Buchholz Relay. Magnetic Oil level Gauge. Explosion Vent.

Transformer Losses and Efficiency Core/Iron Loss =V12 / Rc1 Copper Loss = I12 R1+ I22 R2 Definition of % efficiency = load power factor Transformer

Maximum Transformer Efficiency The efficiency varies as with respect to 2 independent quantities namely, current and power factor Thus at any particular power factor, the efficiency is maximum if core loss = copper loss .This can be obtained by differentiating the expression of efficiency with respect to I2 assuming power factor, and all the voltages constant. At any particular I2 maximum efficiency happens at unity power factor. This can be obtained by differentiating the expression of efficiency with respect to power factor, and assuming I2 and all the voltages constant. Maximum efficiency happens when both these conditions are satisfied. Transformer

Maximum efficiency point 100 pf=1 pf= 0.8 pf= 0.6  At this load current core loss = copper loss % full load current Transformer

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