Active power reversal in the main winding of a single phase induction motor

When a single phase induction motor - with a main and an auxiliary winding - operates in a practical no-load condition, the main winding does not extract active power from the grid but it injects active power into the grid. Active power is transferred from the auxiliary winding to the main winding and injected back in the grid. Using the steady-state equivalent circuit of the motor, this power reversal phenomenon is studied. Formulas, describing the motor behaviour, allow to simulate the power reversal phenomenon using MATLAB.