To deliver 1 kVA of power with a transformer operating at 95% efficiency, how much power in VA is required from the primary?

To determine the amount of power required from the primary side of the transformer, we start by relating the output power to the primary power input in the context of efficiency. Given that the transformer operates at 95% efficiency, we can use the following formula:

Efficiency (η) = (Output Power) / (Input Power)

In this case, the output power is 1 kVA, which is equal to 1000 VA. Rearranging the formula gives us:

Input Power = Output Power / Efficiency

Substituting the known values:

Input Power = 1000 VA / 0.95

Calculating this gives:

Input Power = 1000 VA / 0.95 ≈ 1052.63 VA

When rounded up, this value is approximately 1053 VA. Therefore, to deliver 1 kVA of output power, considering the 95% efficiency of the transformer, the power required from the primary is approximately 1053 VA. This illustrates the impact of efficiency on the design and operation of transformers, highlighting the necessity for engineers and electricians to account for this factor when calculating power requirements for electrical systems.