Examine the name plate details given on the top of the Single phase transformer.
The nameplate shows 3KVA, 110:220V, 50hz.
Single phase step up transformer.
With rated input voltage of 110V, output voltage obtained across secondary is 220V.
Tappings present at 50% & 86.6% at the secondary side.
]]>Primary Tests
Continuity Test
Continuity Test, Voltage Ratio Test and Polarity Test need to be performed sequentially.
For continuity test, use a multimeter to find the continuity of coils and the number of coils.
Note
The selector switch must be in Resistance mode and the two probes of the multimeter connected across the pair of terminals whose continuity is being determined.
If the coils are continuous, the multimeter reading is zero.
If the coils are discontinuous, the multimeter reading is infinity.
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Voltage Ratio Test
Apply 110V input across one of the primary coils.
Use an a.c. voltmeter to find out voltage across the other coil terminals.
Use a voltmeter having multiple ranges (0-150/300/600 V) for the experiment.
The range 0-300V is used for the voltage ratio test.
Note
Turns ratio between the different coils can be derived from the voltage ratio test, using the formula E1/E2 = N1/N2, where E1 and E2 are the induced e.m.f.s across coil 1 and 2, and N1 and N2 are the number of turns of coils 1 and 2.
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Polarity Test
Perform the polarity test for the two primary coils first, by shorting the two coils and measuring the voltage across the open ends.
Perform the polarity test for the secondary coil next, by shorting an end of one of the primary coils with one of the ends of the secondary.
For determining the polarity of the secondary coil, the range of the voltmeter needs to be increased to 600 V.
Note
If the terminals with opposite instantaneous polarity are shorted, there will be a series addition of voltage.
If the terminals with same instantaneous polarity are shorted, there will be a series subtraction of voltage.
]]>Various Connections
(Correct Polarity)]]>
Connect two coils connect them with proper polarity in parallel.
Connect the two dotted ends marked A1 and A3 using a wire & two undotted ends A2 and A4 together using another wire.
Connect 110V power supply across A1 and A2, and measure output and input voltages using a voltmeter of range 0-300V.
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(Incorrect Polarity)]]>
Keeping the same coils in either series or parallel with wrong polarity, connect the coils to the source and see that fuse blows off. Explain Why?
In this case, for parallel operation using incorrect polarity, one dot is connected with another undot terminal i.e. A1 is shorted with A4 and A2 with A3.
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Series Connection
Connect the coils in series by shorting two coils and measure the voltage across the extreme ends.
When A2 and A3 are shorted together, voltage needs to be measured across A1 and A4.
When A2 and A5 are shorted together, voltage needs to be measured across A1 and A6.
For measuring voltage across A1 and A6, the range of the voltmeter has to be increased to 600V.
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D.C.Supply
Connect the same coils to a DC source and again see what happens.
The Fuse blows off. Explain why?
]]>Load Transformer
Load Transformer
Using Two Coils as Setup Transformer, load the secondary till load current has reached maximum as per calculation keeping Fuse intact.
Connect the two primary coils in parallel.
Connect an ammeter in series with each of the primary coil windings to measure the individual primary coil current.
Connect one ammeter in series with the transformer primary side to measure the total current in the primary circuit.
Connect a load box and ammeter to the secondary.
Increase load in steps of 2V and note down all the ammeter readings for each step.
]]>Autotransformer
Autotransformer
Use all the coils to make an Auto Transformer. Load them as in Run III and measure all the data using Voltmeter and Ammeter.
Short A2 with A3 and A4 with A5.
Connect 110V supply across A1 and A2.
Use voltmeter with a range of 600V when measuring the voltage across the extreme points.