Download step-up transformer

HASMUKH GOSWAMI COLLEGE OF
ENGINEERING
TOPIC :- Transformer
PREPARED BY,
Radadiya Radhika L. 140240109506
Champaneri Shubham R.150243109501
Patel Jaimin S. 150243109014
Shrimali Chirag J. 150243109502
Tripathi Aman N. 150243109021
Guided by,
Niketan Dobriya
Electrical DEPARTMENT
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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
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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
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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
Input voltage
Output voltage
(a.c.)
(a.c.)
Primary coil
Secondary coil
All transformers have three parts:
1. Primary coil – the incoming voltage Vp (voltage
across primary coil) is connected across this
coil.
2. Secondary coil – this provides the output
voltage Vs (voltage across the secondary coil)
to the external circuit.
3. 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
Formula for Transformer
voltage across the primary coil
number of turns on primary

voltage across the secondary coil number of turns on secondary
Vp
Vs

Np
Ns
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
Assume we have flux m in magnetic material.
Then flux linking coil 1 having N1 turns is:
1  N1m , and similarly
d m
d 1
v1 
d m
dt
dt
v1

N1
 N1
dt
v2

N2
, v2

2  N 2m
d 2

dt
d m
 N2
dt
V1
N1

 a = turns ratio
V2
N2
12
Worked example No. 1
The diagram shows a transformer. Calculate the voltage
across the secondary coil of this transformer.
Step-up transformer!
Solution
VP N P

VS N S
Substituting
12 180

VS 540
Crossmultiplying
180.VS  12 x 540
12 x 540
 VS 
180
 VS  36 V
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
VS = 6 V
NP = 1380
NS = ?
Obviously, a Step-down transformer!!
Solution
VP N P

VS N S
Substituting
230 1380

6
NS
Crossmultiplying
2300.N S  6 x 13800
6 x 1380
 NS 
230
 N S  36 turns
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
•Transformer Losses
•Core/Iron Loss =V12 / Rc1
•Copper Loss = I12 R1+ I22 R2
Definition of % efficiency


V2 I 2Cos 2
*100
Losses  V2 I 2Cos 2
V2 I 2Cos 2
V12

/ Rc1  I12 R1
 I 2 R2  V2 I 2Cos 2
2
V2 I 2Cos 2
V12
/ Rc1  I 2 Req 2  V2 I 2Cos 2
2
Cos 2
*100
*100
= load power factor
Transformer
20
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
21
Maximum efficiency point
100
pf=1
pf= 0.8
pf= 0.6

At this load current
core loss = copper loss
0
% full load current
Transformer
22
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