Skew leakage in induction machines

Most induction motors have their rotor slots skewed, i. e. twisted away from the axial direction, with the intention to reduce harmful slot harmonic effects. As skewing affects the magnetic coupling between primary and secondary windings, also the fundamental harmonic performance is involved. The latter effect can be expressed for the wound‐rotor type by various modifications of the equivalent circuit, each of which corresponds with a pair of imaginary reference windings. The scaling law of the skew leakage reactance is discussed and compared with the scaling laws of the other leakage reactance components. For cage induction machines, special attention is paid to the omission of rotor bar insulation, its connection with the capricious character of skew leakage and its representation in the equivalent circuit.