Transformer Power
Apparent & real power
Enter winding voltage, current and power factor; VA and W appear live.
V
PF
Power
How to use this calculator
Apparent power is voltage times current: VA = V × I. Real (useful) power is apparent power times the power factor: W = VA × PF. Enter the winding voltage, the current, and a power factor between 0 and 1, and both values appear live.
What it means in a real circuit
VA tells you how much the transformer must be rated to carry; W tells you how much is actually delivered to the load. A power factor of 1 (purely resistive load) means VA = W; inductive or capacitive loads have PF < 1, so the transformer carries more VA than it delivers as W. Use this to check that a transformer's rating covers the load's VA, and to see how much "headroom" the power factor consumes.
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