Circuit model of Transformer

1. 2.4 Circuit model of transformer
P.MARIA SHEEBA
AP/ECE
MZCET

2. Transformer test
• The performance of a transformer can be calculated on the
basis of equivalent circuit.
• The four main parameters of equivalent circuit are:
• - R01 as referred to primary (or secondary R02)
• - the equivalent leakage reactance X01 as referred to
primary (or secondary X02)
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 2

3. • - Magnetising susceptance B0 ( or reactance X0)
• - core loss conductance G0 (or resistance R0)
• The above constants can be easily determined by
two tests
1. OC Test
2. SC Test
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 3

4. • - Open circuit test (O.C test / No load test)
• - Short circuit test (S.C test/Impedance
test)
• These tests are economical and convenient
• - these tests furnish the result without
actually loading the transformer
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 4

5. Open-circuit Test
• In Open Circuit Test the transformer’s secondary winding is
open-circuited, and its primary winding is connected to a full-
rated line voltage.
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 5

6. Usually conducted on H.V side
• To find
(i) No load loss or core loss
(ii) No load current Io which is helpful in finding Go(or
Ro ) and Bo (or Xo )
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 6

7. Short-circuit Test
• Secondary terminals are short circuited
• Primary terminals are connected to a fairly low-voltage
source.
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 7

8. • Usually conducted on L.V side
• To find
(i) Full load copper loss – to pre determine the
efficiency
(ii) Z01 or Z02; X01 or X02; R01 or R02 - to predetermine
the voltage regulation
2.7
MZCET/ECE/III Sem/EE6352- Unit 2 8

9. 2
01
2
0101
01
2
sc
01
01
2
sc
X
W
R
WlossculoadFull
RZ
I
V
Z
I
RI
sc
sc
sc
sc




2.7
MZCET/ECE/III Sem/EE6352- Unit 2 9

10. Losses in transformer
• Core loss (iron loss)
- due to hysteresis.
• Copper loss (I2R loss)
-Resistive heating.
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 10

11. Core loss (iron loss)
• Copper losses are the resistive heating losses
in the primary and secondary windings of the
transformer.
• Hysteresis loss =
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 11

12. Copper loss (I2R loss)2.8
MZCET/ECE/III Sem/EE6352- Unit 2 12

13. • Total loss =iron loss+copper loss
• Iron loss- Due to voltage
• Copper loss-Due to current
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 13

14. Regulation of transformer
• Full load Voltage Regulation is a quantity that compares the
output voltage at no load with the output voltage at full load.
voltageload-no
voltageload-fullvoltageload-no
regulationVoltage


2.8
MZCET/ECE/III Sem/EE6352- Unit 2 14

15. • E2-Secondary terminal voltage on no load
• V2-Secondary terminal voltage onGiven load
Then
MZCET/ECE/III Sem/EE6352- Unit 2 15

16. • I2 – Full load secondary current
. V2- No load secondary Voltage.
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 16

17. • R2e- Equivalent resistance refer to secondary.
• X2e- Equivalent reactance refer to secondary.
• Cos∅ – Power factor
2.8
MZCET/ECE/III Sem/EE6352- Unit 2 17

18. 2.8
MZCET/ECE/III Sem/EE6352- Unit 2 18

19. 2.8
MZCET/ECE/III Sem/EE6352- Unit 2 19