This paper studies parasitic torques in steady-state torque-slip curves of squirrel-cageinduction motors. The curves of nine motors (small, medium and large size units), three of whichwere measured in the range s = 2 to s = 0, are analyzed. The torque-slip curves of eight of thesenine motors differ significantly from the smooth curves predicted by the classical single- anddouble-cage models: a torque dip at large slips in the motoring regime and a noticeable torqueincrease in the braking regime occur. As parasitic torques have been traditionally associated withspace harmonics, two single-cage chain models (which consider the space harmonics) are tested tofit the measured torque and current of the three measured motors: one neglects the skin effect,leading to the wrong torque prediction while the other (the classical chain model in the literature)considers the skin effect, leading to an accurate torque prediction.
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