Polarity and Transformation Ratio Test on Single Phase Transformer

POLARITY & TRANSFORMATION RATIO TEST ON SINGLE PHASE TRANSFORMER

AIM:

To check the polarity of single phase transformer & find the transformation ratio.     

APPARATOUS REQUIRED:

S.No.	Apparatus	Range	Type	Quantity
1	Ammeter
2	Voltmeter
3	Rheostats
4	SPST Switch
5	Tachometer

MACHINES DETAILS:

THEORY : 

Transformation Test

The transformation ratio ‘K’ is equal to the number of turns in the secondary divided by the number of turns in the primary OR it is the ratio of induced emf in the secondary to induced emf in the primary.

ie, K=N₂/N₁ =E₂/E₁

Polarity Test

In a transformer one terminal of primary side is positive with respect to other at every instant. for the secondary side also one terminal of primary side is positive with respect  to other at every instant. If the polarity of terminals is not marked, polarity test is performed to determine the terminals which have some instant polarity. The polarity of the transformer winding is important for practical operation.

The voltmeter reads V₁+V₂ , The transformer is said to posses additive polarity. The voltmeter reads V₁-V₂ , The transformer is said to posses substractive  polarity.

PRECAUTIONS:

PROCEDURE:

• Connections are made as per the circuit diagram.
• Auto transformer is kept in minimum position & supply is given.
• Vary the auto transformer & take different readings till  it exceeds the rated value of voltage 110V.
• Note the voltmeter reading V1,V2& V3. If  V3=V1+V2, then it is additive polarity otherwise it is subtractive polarity.
• Bring the auto transformer to minimum position & switch off the supply.

CIRCUIT DIAGRAM

ADDITIVE POLARITY

SUBSTRACTIVE POLARITY

TRANSFORMATION  RATIO TEST

TABULAR COLUMN:

Additive polarity

Sl no.	V1	V2	V3

Substractive polarity

Sl no.	V1	V2	V3

Transformation ratio test

Sl no.	V1	V2	K=V2/V1

SAMPLE GRAPH :

RESULT: