EXPERIMENT 16 AIM : TO FIND THE POLARITY AND TURNS RATIO OF A SINGLE PHASE TRANSFORMER.

 OBJECTIVE 

1. It will check polarity of  Equal as well as Nonequal Transformer.
2. It will find transformer and its specification.

APPARATUS: 

1. voltmeter                            2 Nos.,
2. Testing Board,                    2 Nos,
3. Digital Multimeter               1 Nos
4. Transformer 240 v/110v     1 Nos

Tools

1. Hand Tools Kit
2. Wire Stripper

THEORY: 

It is essential to know the relative polarity at any instant of primary and secondary terminals for making correct connections. When the two transformers are to be connected in parallel to share the load on the system. The marking is correct if voltage V3 is less than V1, such a polarity is termed as subtractive polarity. The standard practice is to have subtractive polarity because it reduces the voltage stress between adjacent loads. In case V3 > V1, the EMF induced in primary and secondary have additive relation and transformer is said to have additive polarity.

CIRCUIT DIAGRAM

PROCEDURE: 

a) Polarity test:

1.  Connect the circuit as shown in the diagram. 
2.  Switch on the single phase a.c. supply. 
3.  Record the voltages V1, V2 and V3. In case V3 1 polarity is additive. 
4.  Switch off the a.c. supply 

b) Turn Ratio Test: 

1. Connect the circuit as shown in the diagram. 
2. Switch on the a.c. supply. 
3. Record voltage V1 across primary and V2 across various tappings of secondary. 
4. If V1>V2 then transformer is step down. 
5. If V2> V1 then transformer is step up. 
6. Switch off a.c. supply

 

RESULT: 

If V2>V1 then transformer is step up otherwise step down.

PRECAUTIONS:

1. All connections should be tight. 

2. The circuit should be according to circuit diagram. 

3. The power should be on when the circuit is checked completely

QUIZ:

Q1	What is transformer?
A1	Transformer is a static device which is used to change the level of voltage or current without changing the frequency and power.
Q2	What do you mean by turns ratio of transformer?
A2	Turns ratio of a transformer is the ratio of primary turns to the secondary turns.
Q3	What is transformation ratio of transformer?
A3	Transformation ratio is the ratio of secondary side turns to primary side turns.
Q4	What are the different polarities of transformer?
A4	Positive and negative polarity.
Q5	What is the condition of additive polarity?
A5	When the sum of voltages is more than individual voltages, then it is called additive
Q6	What is the condition for subtractive polarity.
A6	When the sum of voltages is less than individual voltages, then it is called subtractive
Q7	What are the different types of transformer?
A7	The different types of transformer are : step up and step down
Q8	What is the use of autotransformer?
A8	Autotransformer is used for increasing or decreasing the voltage with the use of one winding
Q9	What is the use of polarity test?
Q9	The polarity test is performed to find the positive and negative polarity of transformer.