To study load test on single phase transformer and determine efficiency and voltage regulation of a single phase transformer.

Experiment No.: – 17

Aim of the Experiment: –

To study load test on single phase transformer and determine efficiency and voltage
regulation of a single phase transformer.

Apparatus Required: –

Sl. No.NameSpecificationQuantity
1Single-phase Auto-transformer(0-270)V, 3KVA, 30A1 no.
2Singe Phase Transfoormer230/230, 3 KVA1 no.
3Wattmeter(0-150/300/600)V, 10A/20A, Dynamometer type, UPF1 no.
4Ammeter(0-5/10/20)A, MI1 no.
5Voltmeter(0-150/300/600)V, MI1 no.
6Resistive Load2 KW1 no.
7Connecting WirePVC Insulated CopperAs per required
Table No. 17.1

Circuit Diagram: –

Fig. No. 17.1

Theory: –

When the secondary winding of a transformer is connected to a load and a voltage V is
applied to the primary winding, the transformer is said to be operated under load condition. Under this condition transformer cupper loss increases with increase in current . So efficiency changes. Maximum efficiency point reaches when Iron loss is equal to copper loss. Iron loss is constant for a transformer, therefore at maximum point copper loss is very less & equal to iron loss. Near to half load efficiency reaches to next peak point & it gradually decreases when further load increases. When load increases beyond half load copper loss will increase which reduces the efficiency. This situation happens when transformer is distribution type transformer.

Precautions: –

  1. Do not switch on supply without concerning respected teachers.
  1. Single phase Auto transformer must be kept at minimum potential point.
  2. Primary voltage that is V1 should always be constant throughout the experiment.

Procedures: –

  1. Make the connection as shown in the diagram keeping the auto-transformer in zero
    position and all switches and load is in off position.
  1. Switch on the AC supply and then vary the voltage up to rated voltage of the transformer.
  2. Now, start loading the transformer by putting on load switch on. So that a suitable current is obtained.
  3. And then change the load and note down the reading of all the instrument.
  4. Here the primary voltage of the transformer should always be in rated voltage
    irrespective of load.

Observation Table for Open Circuit Test: –

Sl. No.Load
in Watts.		V1 in Volts.I1 in Amps.W1 in Watts.V2 in Volts.I2 in Amps.W2 in Watts.% Efficiency% Voltage Regulation
1
2
3
4
5
6
7
8
9
10
Table No. 17.2

Calculations:

\[\color\red{\%\; Efficiency\;=\;}{\color\green{\dfrac{Output\;Power}{Input\;Power}\;X\;100}}\] \[\color\red{\;=\;\dfrac{W_2}{W_1}\;X\;100}\] \[\color\red{\;\%\;Voltage\;Regulation\;=}\color\green{\dfrac{V_1-V_2}{V_0}\;X\;100}\]

Conclusion: –

To be written by Student.

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