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Document 1920105
DEHRADUN INSTITUTE OF TECHNOLOGY
LABORATORY MANUAL
PRACTICAL INSTRUCTION SHEET
EXPERIMENT TITLE : OC & SC test on 1-phase transformer
EXPERIMENT NO. :
ISSUE NO. :
ISSUE DATE :
REV. NO. V
REV. DATE : 01/01/2016
PAGE
DEPTT. : Electrical
Engineering
LABORATORY : Intro to Electrical & Electronics Lab
EA1210
/
SEMESTER : I / II
Objective: - To perform open circuit (OC) & short circuit (SC) test on single phase transformer and
calculate the followings.
a. Complete parameters of equivalent circuit.
b. Efficiency at half of the full load and at unity power factor.
Apparatus Used: - One single phase transformer 2 kVA, 230/230 volts and following apparatus
5
6
7
Type
Range
15A, 230/0-270
Volts
MI
0-1 A
MI
0-250 V
Dynamometer 1 A, 250 V
Wattmeter
(High PF)
Dynamometer 5 A, 75 V
MI
MI
Quantity
1
1
1
1
0-5 A
0-30 V
1
1
1
For OC
test
2
3
4
Name
Single phase
autotransformer
Ammeter
Voltmeter
Wattmeter
(Low PF 0.2)
Ammeter
Voltmeter
For SC Test
S.No
1
Theory:
1. Open Circuit (OC) test or No load test:
By OC test we can find out
 Iron losses (Pi)
 No load current (I0)
 Cosϕ0, Ie, Im, R0 & X0
Wattmeter
1-Phase Auto
Auto
Transformer
CC
M
L
A
COM
PC
V
V
Rated Voltage
Figure: 1
PREPEARD BY :-
Mr. Nafees Ahmed
LV
APPROVED BY :- Dr. Gagan Singh
Visit us at www.eedofdit.weebly.com
HV
DEHRADUN INSTITUTE OF TECHNOLOGY
LABORATORY MANUAL
PRACTICAL INSTRUCTION SHEET
EXPERIMENT TITLE : OC & SC test on 1-phase transformer
EXPERIMENT NO. :
ISSUE NO. :
ISSUE DATE :
REV. NO. V
REV. DATE : 01/01/2016
PAGE
DEPTT. : Electrical
Engineering
LABORATORY : Intro to Electrical & Electronics Lab
EA1210
Iron losses
No load current
Let
/
SEMESTER : I / II
Pi = Reading of wattmeter (P0)
I0 = Reading of Ammeter
V = Reading of voltmeter
P0 = Pi = VI0Cosϕ0
P
 Cos0  i
VI0
Ie = I0Cosϕ0
Im = I0Sinϕ0
V
V
R0 
& X0 
Im
Ie
Note:
(i)
(ii)
Rated voltage is applied at LV side.
This test is generally done on LV side (Why?)
2. Short Circuit (SC) test:
By SC test we can find out
 Copper losses (PC)
 Equivalent resistance or leakage reactance (R01 & X01 OR R02 & X02) referred to
metering side.
Full load Cu losses
PC = Reading of wattmeter (Wsc)
Let
Short circuit current Isc = Reading of Ammeter
Short circuit voltage Vsc = Reading of voltmeter
Wattmeter
CC
COM
PC
L
V
Rated Current
HV
LV
Figure: 2
PREPEARD BY :-
Mr. Nafees Ahmed
APPROVED BY :- Dr. Gagan Singh
Visit us at www.eedofdit.weebly.com
Shorted
V
d
1-Phase Auto
Auto
Transformer
M
A
DEHRADUN INSTITUTE OF TECHNOLOGY
LABORATORY MANUAL
PRACTICAL INSTRUCTION SHEET
EXPERIMENT TITLE : OC & SC test on 1-phase transformer
EXPERIMENT NO. :
ISSUE NO. :
ISSUE DATE :
REV. NO. V
REV. DATE : 01/01/2016
PAGE
DEPTT. : Electrical
Engineering
LABORATORY : Intro to Electrical & Electronics Lab
EA1210
R
Z
Wsc  I sc2 Req
Vsc  I sc Z eq
 R01 or R02 
eq  Z 01 or Z 02
eq
X
X eq  Z eq2  Req2
eq
/
SEMESTER : I / II

 X 01 or X 02 
Note:
(i)
(ii)
(iii)
(iv)
Rated Current is applied at HV side.
This test is generally done on HV side (Why?)
Why the position of ammeter and voltmeter is changed as compared to OC test?
Why com terminal of wattmeter is connected with terminal L not with terminal M?
3. Efficiency of transformer:
Efficiency at x time of full load

xP2
 100
xP2  Pi  x 2 PC
Where
P2  V2 I 2 Cos 2  Rated VA  Cos 2
Cos 2  Load PF
Circuit Diagram:- See figure 1 & 2
Observation table:OC Test
Pi or P0
(W)
PREPEARD BY :-
V
(V)
SC Test
I0
(A)
Mr. Nafees Ahmed
Pc or Wsc
(W)
Vsc
(V)
APPROVED BY :- Dr. Gagan Singh
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Isc
(A)
DEHRADUN INSTITUTE OF TECHNOLOGY
LABORATORY MANUAL
PRACTICAL INSTRUCTION SHEET
EXPERIMENT TITLE : OC & SC test on 1-phase transformer
EXPERIMENT NO. :
ISSUE NO. :
ISSUE DATE :
REV. NO. V
REV. DATE : 01/01/2016
PAGE
DEPTT. : Electrical
Engineering
LABORATORY : Intro to Electrical & Electronics Lab
EA1210
/
SEMESTER : I / II
Calculation:Equivalent circuit of transformer:
R01
X01
KI2
I0
Im
Ie
V1
For OC test: find MF
R0
X0
V2/K
L
O
A
D
Figure 3: Approximately & simplified Equivalent
Circuit Referred to primary side
Multiplying Factor (M.F.) =
VI Cos
Full scale deflection (FSD)
Cos 0 
cos  0.2
Pi
VI 0
Ie = I0Cosϕ0
Im=I0Sinϕ0
R0 
V
V
& X0 
Im
Ie
For SC test: find MF
Multiplying Factor (M.F.) =
VI Cos
Full scale deflection (FSD)
Wsc  I sc2 Req
Vsc  I sc Z eq
X eq  Z eq2  Req2
PREPEARD BY :-
Mr. Nafees Ahmed
R
Z
eq
 R01 or R02 
eq
 Z 01 or Z 02 
X
eq
 X 01 or X 02 
APPROVED BY :- Dr. Gagan Singh
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cos 1
DEHRADUN INSTITUTE OF TECHNOLOGY
LABORATORY MANUAL
PRACTICAL INSTRUCTION SHEET
EXPERIMENT TITLE : OC & SC test on 1-phase transformer
EXPERIMENT NO. :
ISSUE NO. :
ISSUE DATE :
REV. NO. V
REV. DATE : 01/01/2016
PAGE
DEPTT. : Electrical
Engineering
LABORATORY : Intro to Electrical & Electronics Lab
EA1210
/
SEMESTER : I / II
Efficiency at full load: x =1 & PF = 1

P2
 100
P2  Pi  PC
Where
P2  V2 I 2 Cos2  Rated VA  Cos2
Result: - The OC & SC test has been performed on given transformer and the calculated value of equivalent
parameters & efficiency is given in following table
Iron
Loss (Pi)
(W)
From OC Test
No load
No Load
Current
PF
I0 (A)
Cos0
X0
(Ω)
R0
(Ω)
From SC Test
Full load cu
Req
loss Pc (W)
(Ω)
Xeq
(Ω)
Efficiency
(%)
Precautions:1. In SC test applied voltage is very less to get the rated short circuit current. Don’t give rated
voltage otherwise very high current will follow and system will get damage.
2. Make sure that auto transformer is at zero position.
3. The main switch should be at off position before doing the connections.
4. All connection should be tight and clean.
5. The reading in instruments should not exceed from their permissible limit.
6. Don’t touch the necked terminals as voltage is high.
7. Always wear shoes when working in the lab. Avoid wearing loose clothes, hanging chains
etc.
PREPEARD BY :-
Mr. Nafees Ahmed
APPROVED BY :- Dr. Gagan Singh
Visit us at www.eedofdit.weebly.com
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