Theory of the doubly-fed induction machine in the steady state

This paper presents a fundamental steady-state theory of the doubly-fed induction machine, including its analogy with the classical synchronous machine. Formulas for the real and reactive powers at the stator and rotor terminals are derived in a form suitable for machine design calculations. The formulas show the relationship between the voltage applied at the rotor terminals and the real and reactive power flows, providing a useful link between machine-design calculations and external system simulation. The theory is developed from first principles using phasors, and includes many details that are missing or obscure in the classical works on induction machines.