4
JL/X130 - 1680
2.1.3 Rotor Control to optimise torque across speed range
The diagram shows all 4 quadrants of Speed against Torque, with curves for a shorted rotor and for 4 other
values of rotor resistance. This diagram is of course a simplistic representation to facilitate the explanation of
the control strategy.
For a high Rotor resistance (R1 + R2 + R3 + R4 + R5) the starting torque is high but the torque at higher
speeds reduces.
For a shorted Rotor the starting torque is low but the torque at higher speeds increases.
There is a family of curves inbetween. The JL/X automatically selects the appropriate Rotor resistance using
the contactor outputs to keep the torque curve at maximum throughout the speed range.
Speed / Torque
curve for
shorted Rotor
Speed / Torque
curve for R1
Speed / Torque
curve for
R1 + R2 + R3
Speed / Torque curve
for
R1 + R2 + R3 + R4
Speed / Torque
curve for
R1 + R2
Speed / Torque curve for
R1 + R2 + R3 + R4 + R5
