In a recent contribution, the authors have shown that field-oriented contro
llers for induction motors preserve stability under a wide range of variati
ons of the motor and controller parameters. However, as is well known, the
transient performance critically depends on the tuning of the gains of the
proportional-integral (PI) velocity loop, a task which is rendered difficul
t because of the high uncertainty on the rotor resistance. The problem me a
ddress in this paper is how to develop an offline procedure to choose these
gains. The main contribution of our work is a very simple frequency-domain
test that, for each setting of the PI gains, evaluates the maximum range o
f the relative rotor resistance estimate for which global stability is guar
anteed. In this may, we provide a quantitative estimate of the performance
of the PI controller. The stability result may also be used in a dual manne
r, fixing now the range of the rotor resistance, and estimating an admissib
le interval for the PI gains that preserves global stability. Instrumental
for our study is the exploitation of an energy dissipation (strict passivit
y) property of the system.