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To conduct Open circuit and Short circuit tests on single phase transformer
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Electrical Lab Experiments

To conduct Open circuit and Short circuit tests on single phase transformer



AIM:

To conduct Open circuit and Short circuit tests on single phase transformer to pre-determine the efficiency, regulation and equivalent parameters.

Name Plate Details:

Oc & Sc Tests On Single Phase Transformer

Apparatus Required:

Oc & Sc Tests On Single Phase Transformer

Circuit Diagram:

Open Circuit Test:

Oc & Sc Tests On Single Phase Transformer

Short Circuit Test:

Oc & Sc Tests On Single Phase Transformer

Theory:

Transformer is a device which transforms the energy from one circuit to other circuit without change of frequency.

The performance of any transformer calculated by conducting tests .OC and SC tests are conducted on transformer to find the efficiency and regulation of the transformer at any desired power factor.

OC Test:

The objectives of OC test are.

  • 1. To find out the constant losses or iron losses of the transformer.
  • 2. To find out the no load equivalent parameters.
h2>SC Test:

The objectives of OC test are.

  • 1. To find out the variable losses or copper losses of the transformer.
  • 2. To find out the short circuit equivalent parameters.

By calculating the losses and equivalent parameters from the above tests the efficiency and regulation can be calculated at any desired power factor.

Procedure (OC Test):

  • 1. Connections are made as per the circuit diagram.
  • 2. Initially variac should be kept in its minimum position.
  • 3. Close the DPST switch.
  • 4. By varying Auto transformer bring the voltage to rated voltage.
  • 5. When the voltage in the voltmeter is equal to the rated voltage of HV winding note down all the readings of the meters.
  • 6. After taking all the readings bring the variac to its minimum position.
  • 7. Now switch off the supply by opening the DPST switch.

Procedure (SC Test):

  • 1. Connections are made as per the circuit diagram.
  • 2. Short the LV side and connect the meters on HV side
  • 3. Before taking the single phase, 230 V, 50 Hz supply the variac should be in minimum position.
  • 4. Now close the DPST switch so that the supply is given to the transformer.
  • 5. By varying the variac when the ammeter shows the rated current (i.e. 13.6A) then note down all the readings.
  • 6. Bring the variac to minimum position after taking the readings and switch off the supply.

OC Test Observation:

Oc & Sc Tests On Single Phase Transformer

SC Test Observation:

Oc & Sc Tests On Single Phase Transformer

Calculation:

(a)Calculation of Equivalent circuit parameters:

Let the transformer be the step down transformer.

(i)Parameters Calculation from OC test:

Oc & Sc Tests On Single Phase Transformer

(ii)Parameters Calculation from SC test:

Oc & Sc Tests On Single Phase Transformer

(a)Calculations to find efficiency:

Oc & Sc Tests On Single Phase Transformer

(a)Calculation of Regulation at full load:

Oc & Sc Tests On Single Phase Transformer

Tabular Column:

Oc & Sc Tests On Single Phase Transformer

Tabular Column:

Oc & Sc Tests On Single Phase Transformer

Model Graphs:

1. Efficiency Vs Output

Oc & Sc Tests On Single Phase Transformer

1. Regulation Vs Power Factor

Oc & Sc Tests On Single Phase Transformer

Result:

Viva Questions:

  • 1) What is a transformer?
  • 2) Draw the equivalent circuit of transformer?
  • 3) What is the efficiency and regulation of transformer?