Answer:
The given question contains multiple parts, each asking for a different calculation or analysis related to the given transformer. I will try to address each part of the question separately:
a) To find the equivalent circuit of the transformer referred to the low-voltage side, we need to know the transformer's equivalent impedance and leakage reactance. These can be calculated using the open-circuit and short-circuit test data. The equivalent impedance can be calculated using the following formula:
Zeq = (Voc^2 / Poc) - (Iso^2 * Rc)
Where Rc is the core loss resistance, which can be assumed to be negligible.
The leakage reactance can be calculated using the following formula:
Xm = (Vsc / Iso) - Rc
Once these values have been calculated, we can create the equivalent circuit of the transformer, which consists of a series connection of the equivalent impedance and leakage reactance, connected in parallel with the magnetizing reactance (Xm).
b) To calculate the full-load voltage regulation at unity power factor, we can use the following formula:
Voltage regulation = (Voc - Vsc) / Voc
c) I would plot the voltage regulation as lead is increased from no load to full load under condition b, but as it is not specified how the voltage regulation varies with the load, I am unable to provide the plot.
d) To calculate the efficiency of the transformer at full load with a power factor of 0.6 lagging, we can use the following formula:
Efficiency = (Output power (at 0.6 pf lagging) / Input power) * 100
Where the output power can be calculated using the following formula:
Output power = (Vsc * Iso * cos(theta))
Where theta is the angle between the voltage and current at the secondary side (in this case, the low-voltage side) of the transformer.
It is worth noting that these calculations require accurate data for the transformer's voltage and current values, as well as the core loss resistance, and assuming the data provided is accurate the above formulas will give you the desired results.