The DVDF (double voltage double frequency) test is an overvoltage withstand test. It is performed by applying a higher than nominal voltage (2 times) to the transformer for a relatively short period of time (usually 1 minute). Since a prolonged (significant) overvoltage will cause the transformer to overexcite, the volts per hertz are kept constant by applying a higher than nominal frequency (2 times in this case).
why need dielectric test for transformer
Short circuit test and open circuit test are widely used to test the efficiency of the transformer.
Check that the input and output voltages are as required. Check that the transformer is big enough for the current required for the unit you have.
Procedure for sumpners test is the single phase transformer. This is a back to back test.
in electrical engineering
These two tests are performed on a transformer to determine (i) equivalent circuit of transformer(ii)voltage regulation of transformer(iii) efficiency of transformer. The power required for theseOpen Circuit test and Short Circuit test on transformeris equal to the power loss occurring in the transformer.
why need dielectric test for transformer
Short circuit test and open circuit test are widely used to test the efficiency of the transformer.
The supply is given on the high voltage side of transformer because the supply voltage required to circulate rated current through the transformer is usually very small So energy is saved.
first is isolation test with 4.5 kv or above as per the custumer had asked between primary and secondary.also to find the leakege inductance its test is required for both primary and secondary.find the megnetising inductance between two winding(or say coupling )
since we need to get desired or rated voltage, so if it is connected in high voltage side of the transformer, voltage supply will be more, and hence the current will be more than the required amount. this is the reason why the instruments re connected at the low voltage of the transformer while performing no load test.
The open/short-circuit test on a transformer isn't 'needed'. It's only used if you want to find out the efficiency of a transformer.
Check that the input and output voltages are as required. Check that the transformer is big enough for the current required for the unit you have.
to determine the transformer characteristics...
Depends on the kva rating of the devices to be tested using a transformer.
A short-circuit test is done to determine the power lost in the resistance of the primary and secondary windings of the transformer. It is done at full load current but with only enough voltage to give the required current with the secondary short circuited. An open-circuit test is done at full load voltage but no current is taken from the secondary, and this enables the power lost in the magnetic core of the transformer to be measured. As well a power, the tests also allow the inductances to be measured as well as the resistances, in order ot characterise the transformer fully.
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