1. Air-Gap Power
The power transferred electromagnetically across the air gap between the stator and rotor is called the “air-gap power”, or “gap power”. We will consider one phase as shown above.
ECE 441

2. Active Power (Watts)
Reactive Power (VARS)
ECE 441

3. Power Components
Active Power, Pgap, supplies the shaft power output as well as friction, windage, and heat losses in the rotor.
Reactive Power, Qgap, supplies the reactive power component for the alternating magnetic field around the rotor current. Reactive power is not dissipated, but is sinusoidal across the gap.
ECE 441

4. Power Diagram for Air-Gap Power
ECE 441

5. ECE 441