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Proportional-integral (PI) controllers in a positive-sequence (PS) synchronous reference frame (SRF) are widely employed for ac machines. Resonant controllers (RCs) in stationary frame are equivalent to PI ones in a positive- and a negative-sequence SRF simultaneously. However, as shown in this work, the additional open-loop pole at the negative-sequence in RCs alters the trajectories of the closed-loop poles, with respect to PS-SRF-PI controllers. This paper compares the transient response provided by RCs with that of PS-SRF-PI controllers. It is shown that RCs produce transitory torque oscillations, which increase the overshoot and settling time in certain conditions, and present a greater cross-coupling between flux and torque.