It seems like you're asking about transformers and their efficiency. Transformers are devices used to transfer electrical energy between two or more circuits through electromagnetic induction. The efficiency of a transformer is an important factor as it determines how effectively it can convert input electrical power into output electrical power.
Efficiency (η) of a transformer is given by the formula:
Efficiency (η) = (Output Power / Input Power) * 100
Where,
Output Power is the power delivered to the load (in watts)
Input Power is the power drawn from the source (in watts)
Efficiency is typically highest at or near the rated load of the transformer. However, transformers are not usually rated in terms of efficiency; rather, they are rated in terms of their apparent power capacity, which is measured in volt-amperes (VA) or kilovolt-amperes (kVA).
The rated apparent power capacity of a transformer is the maximum power it can handle while maintaining acceptable levels of temperature rise and performance. It's important to note that apparent power is the product of the voltage and current in the circuit, while real power (in watts) is the actual power used for useful work.
If you're interested in calculating the current (I) at maximum efficiency for a given transformer's kVA rating, you can use the formula:
Apparent Power (S) = Voltage (V) × Current (I)
So, rearranging the formula to solve for current (I):
Current (I) = Apparent Power (S) / Voltage (V)
Keep in mind that this calculation gives you the current at the rated kVA capacity of the transformer, which is where the efficiency is typically highest. The actual current drawn might vary depending on the load connected to the transformer.
For a more accurate assessment of efficiency and current under specific conditions, you would need to consider additional factors like load characteristics, power factor, and the transformer's efficiency curve. Transformers may have different efficiencies at different load levels due to losses like copper losses and iron losses.
If you're working with specific transformer specifications or need more detailed calculations, it's recommended to consult the manufacturer's documentation or seek assistance from an electrical engineer.