Efficiency of Transformer

1. Efficiency of Transformer
P. Maria Sheeba
AP/ECE
MZCET

2. Efficiency
• Transformer efficiency is defined as (applies to motors,
generators and transformers):
%100
in
out
P
P

%100


lossout
out
PP
P

2.8
MZCET/ECE/III Sem/EE6352- Unit 2 2

3. -
• Therefore, for a transformer, efficiency may be calculated
using the following:
%100
cos
cos
x
IVPP
IV
SScoreCu
SS





CopperlossPCu 
CorelossPcore 
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 3

4. Condition for maximum efficiency
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 4

5. 2.8
MZCET/ECE/III Sem/EE6352- Unit 2 5

6. The Condition for maximum efficiency
• The Condition for maximum efficiency is
Copper loss = Core loss
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 6

7. All day efficiency
hours)24(
kWhinInput
kWhinoutput
in wattsinput
in wattsputout
efficiencycommercialordinary
day forall 


•All day efficiency is always less than the
commercial efficiency
2.9
MZCET/ECE/III Sem/EE6352- Unit 2 7

8. Auto transformer
• .
MZCET/ECE/III Sem/EE6352- Unit 2 8
2.10

9. Introduction
• An autotransformer (sometimes
called autostep down transformer) is an
electrical transformer with only one Winding.
MZCET/ECE/III Sem/EE6352- Unit 2 9
2.10

10. • portions of the same winding act as both
the primary and secondery sides of the
transformer.
MZCET/ECE/III Sem/EE6352- Unit 2 10
2.10
Introduction

11. Operation
• An autotransformer has a single
winding with two end terminals.
• The primary voltage is applied
across two of the terminals.
• The secondary voltage taken from
two terminals,
• Almost always having one
terminal in common with the
primary voltage.
MZCET/ECE/III Sem/EE6352- Unit 2 11
2.10

12. Advantages of Autotransformers
• Its efficiency is more when compared with
theconventional one.
• Its size is relatively very smaller.
• Voltage regulation of autotransformer is much better.
• Lower cost
• Low requirements of excitation current.
• Less copper is used in its design and construction
MZCET/ECE/III Sem/EE6352- Unit 2 12
2.10

13. Applications:
1. Used in both synchronous motor and
industrial motors..
2. Used in electrical apparatus testing labs since
the voltage can be smoothly and
continuously varied.
3. They find application as boosters in
AC feeders to increase the voltage levels.
MZCET/ECE/III Sem/EE6352- Unit 2 13
2.10

14. Revision
• Construction of transformer
• Types of transformer
• Equivalent circuit of transformer
• Efficiency of transformer
MZCET/ECE/III Sem/EE6352- Unit 2 14