When no load test is carried out onhv side of 1000/100v single phase transformer with 100v winding open the wattmeter reads 110w if the test is repeated on lv side with 1000v winding open the wattmeter will read?

Question

Answer

110w please explain it how?

Answer

Explanation:

When no load test is carried out on the HV side of a 1000/100V single-phase transformer with 100V winding open, the wattmeter reads 110W. This indicates the iron losses in the transformer core.

If the test is repeated on the LV side with the 1000V winding open, the wattmeter will read a lower value. This is because the iron losses are constant and the copper losses are dependent on the current, which is lower on the LV side due to the higher voltage.

Calculation:

The iron losses in the transformer core are constant and independent of the voltage and current. Therefore, the wattmeter reading on the LV side can be calculated as follows:

Wattmeter reading = Iron losses + Copper losses

Since the iron losses are constant, we can subtract the HV wattmeter reading from the total wattmeter reading to get the copper losses:

Copper losses = Total wattmeter reading - HV wattmeter reading
Copper losses = 110W - 0W = 110W

Now we can calculate the LV wattmeter reading:

Wattmeter reading = Iron losses + Copper losses
Wattmeter reading = 110W + Copper losses

Since the copper losses are lower on the LV side due to the higher voltage, the LV wattmeter reading will be lower than 110W.

Conclusion:

When no load test is carried out on the HV side of a transformer with the LV winding open, the wattmeter reading indicates the iron losses in the transformer core. The wattmeter reading on the LV side will be lower due to the higher voltage and lower current, which results in lower copper losses.

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