Real, reactive, and apparent power and power factor

Separate kW, kvar, and kVA, and explain what correcting power factor does and does not change.

Real power (kW) does work — torque, heat, light. Reactive power (kvar) shuttles energy in and out of magnetic and electric fields without doing net work, but it still occupies conductor and transformer capacity. Apparent power (kVA) is the vector sum, and equipment is rated in kVA because that is what the copper and iron actually carry.

Power factor is kW ÷ kVA — the fraction of the delivered capacity that turns into work. A motor at 0.80 PF drawing 80 kW is occupying 100 kVA of system capacity. Adding capacitors supplies the magnetising reactive power locally, so the same 80 kW arrives while the current upstream falls.

What correction does not do: it does not reduce the real energy the load consumes, and over-correction can push the system leading and cause voltage rise. Correction is a capacity and loss argument, not a free energy argument.

Predicting before you experiment is what makes the result stick. There is no penalty for being wrong here.

Correct a lagging plant load and watch which quantities move and which stay put.

1. Enter a load of roughly 80 kW at 0.80 lagging power factor.
2. Record the apparent power and line current before correction.
3. Add capacitive kvar until the power factor reaches about 0.95.
4. Compare kW, kVA, and current before and after, and note which one did not change.

Explain in your own words why a utility might bill for low power factor even though the customer's kWh consumption is unchanged.