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L4 - Testing of Transformer

The document outlines the procedures for conducting open circuit and short circuit tests on transformers to determine key parameters. The open circuit test measures core loss, no-load current, and other related values, while the short circuit test focuses on full-load copper loss and equivalent resistance and reactance. Both tests are essential for understanding the operational characteristics of transformers under different conditions.

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22 views3 pages

L4 - Testing of Transformer

The document outlines the procedures for conducting open circuit and short circuit tests on transformers to determine key parameters. The open circuit test measures core loss, no-load current, and other related values, while the short circuit test focuses on full-load copper loss and equivalent resistance and reactance. Both tests are essential for understanding the operational characteristics of transformers under different conditions.

Uploaded by

chansara08
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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DETERMINATION OF PARAMETERS OF CIRCUIT MODEL OF TRANSFORMER

1. Open circuit test


2. Short circuit test
(i) Open circuit test:
Open circuit test is useful to determine:
1. Core loss.
2. No-load current.
3. R0 and X0.
 One winding of the transformer usually high voltage winding is left open and the
other winding is connected to the supply of normal voltage and frequency.
 The applied voltage V1 is measured by a voltmeter, the no-load current I0 by an
ammeter and no load input power W0 by a wattmeter.
 As the normal rated voltage is applied to the primary, normal iron loss will occur in
the transformer core.

Fig 2.23: Open Circuit test


 Hence wattmeter will read the iron losses and small copper loss in the primary.
 As the no-load current Io is small, copper losses negligible in primary and nil in
secondary winding.
 Hence, wattmeter reading gives the iron losses in the transformer and it is same at
all loads.
Iron loss Pi = Wattmeter reading =W0
No-load current = Ammeter reading =I0.
Applied voltage = Voltmeter reading =V1
Input power
0 = 1 0 0
No-load power factor

0=

0 =

No-load wattful component


= 0 0 =

No-load magnetising component


= 0 0=

Thus open circuit gives no load loss Pi, Iw, Iμ, R0, X0.
(ii) Short circuit test:
The short circuit test is useful to find:
1. Full-load copper loss.
2. Equivalent resistance and reactance referred to any side.

 In this test, the secondary winding (usually low voltage winding) is short circuited
by a thick conductor and variable low voltage is applied to the primary winding.
 The input voltage is gradually raised with the help of a variac till I sc full load
current flows in the primary winding.
 There is no output from the transformer under short circuit conditions. Since
applied voltage is very low, flux linking with the core is very small and therefore
iron losses are so small that these can be neglected and so the reading of the
wattmeter gives total copper loss at full load.

Full load copper loss Pcu= Wattmeter reading =WS


Applied voltage = voltmeter reading =VSC
Full-load primary current = Ammeter reading = I1.

Pcu = ( 1 + ) =( 01 )

=
Fig 2.24: Short Circuit test

Where R01 is the total resistance of transformer referred to primary.


Total impedance referred to primary

Total leakage reactance referred to primary

X01 =

Short circuit power factor


=

Thus short circuit test gives full load cu loss, X01, R01 and cosФs

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