Correct Answer - Option 2 : apparent power
Apparent power is the product of voltage and current.
Apparent power = VI
The heat produced by the transformer increases with the increase in current.
Therefore, the increase in temperature is directly proportional to apparent power or VA rating of the transformer.
Important Points:
- Sumpner's test is conducted on transformers to determine the increase in temperature.
- It is a non-loading heat run test on transformers.
- The maximum temperature rise in a large transformer is determined by the full load test by measuring the temperature of their oil after every particular interval at a time.
- The full load test on a small transformer is very convenient, but on the large transformer, it is very difficult.
- This test is called, back-to-back test, regenerative test. Two identical transformers are used for the back to back test.
- While performing back to back test, the amount of power consumed is equal to iron and copper losses of two transformer at full load.
