OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER - Code

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Monday, April 4, 2011

OPEN CIRCUIT & SHORT CIRCUIT TEST ON A SINGLE PHASE TRANSFORMER


OPEN CIRCUIT & SHORT CIRCUIT TEST ON A
SINGLE PHASE TRANSFORMER
AIM:
To predetermine the efficiency and regulation of a transformer by conducting open circuit test and short circuit test and to draw equivalent circuit.

APPARATUS REQUIRED:
S.No.
Apparatus
Range
Type
Quantity
1
Ammeter
(0-2)A
(0-5) A
MI
MI
1
1
2
Voltmeter
(0-150)V
MI
2
3
Wattmeter
(150V, 5A)
(150V, 5A)
LPF
UPF
1
1
4
Connecting Wires
2.5sq.mm
Copper
Few

PRECAUTIONS:
  1. Auto Transformer should be in minimum voltage position at the time of closing & opening DPST Switch.




PROCEDURE:
OPEN CIRCUIT TEST:
  1. Connections are made as per the circuit diagram.
  2. After checking the minimum position of Autotransformer, DPST switch is closed.
  3. Auto transformer variac is adjusted get the rated primary voltage.
  4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.
  5. Auto transformer is again brought to minimum position and DPST switch is opened.
SHORT CIRCUIT TEST:
  1. Connections are made as per the circuit diagram.
  2. After checking the minimum position of Autotransformer, DPST switch is closed.
  3. Auto transformer variac is adjusted get the rated primary current.
  4. Voltmeter, Ammeter and Wattmeter readings on primary side are noted.
  5. Auto transformer is again brought to minimum position and DPST switch is opened.



















TABULAR COLUMN:

OPEN CIRCUIT TEST:
Vo
(Volts)
Io
(Amps)
Wo
(Watts)







SHORT CIRCUIT TEST:
Vsc
(Volts)
Isc
(Amps)
Wsc
(Watts)











FORMULAE:
Core loss: Wo =  VoIo cos fo

      Wo                                         Wo
cos fo  =  -------                 fo  = cos-1    -------                       
                 Vo Io                                                  Vo Io
Iw = Io cos fo (Amps)       Im = Io sin fo (Amps)
  X02
 Xo1 =  -------  W
  K2

 
 R02
Ro1 =   -------  W
  K2

 
Vsc
Zo2 =   -------  W
Isc
 
Wsc
Ro2 =   -------  W
Isc2
 
V0
Xo =   -------  W
Im
 
V0
Ro =   -------  W
Iw
 
 








 Xo2 =  ( Zo2 - Ro22)1/2

 



          V2
K=   -------  = 2
          V1

 
 












Percentage Efficiency:     for all loads and p.f.

                            Output Power           (X) x KVA rating x 1000 x cos f
Efficiency h% = -------------------- =  ------------------------------------------------
                              Input Power                   Output power + losses

                                                                         (X) x KVA rating x 1000 x cos f
        =  -------------------------------------------------------------
                                                           (X) x KVA rating x 1000 x cos f + Wo + X2Wsc

Percentage Regulation:
+  = lagging
-  = leading
 
(X) x Isc (Ro2 cos f ± Xo2sin f) x 100  
                                    R% =  --------------------------------------
                                                                        V2

 Where X is the load and it is 1 for full load,  ½  for half load, ¾ load, ¼ load etc.. and the power factor is, upf, o.8 p.f lag and 0.8 p.f lead






EQUIVALENT CIRCUIT:




MODEL GRAPHS:










 






















RESULT:
Thus the efficiency and regulation of a transformer is predetermined by conducting open circuit test and short circuit test and the equivalent circuit is drawn.

3 comments:

  1. you are doing a great job... thanx... Please keep it up..

    ReplyDelete
  2. thanks for the great job.
    i would suggest for the viva questions also

    ReplyDelete