Torque controller for an AC motor drive and AC motor drive embodying the same

摘要

In an induction motor drive a signal representative of the torque T as derived by sensing only the stator armature current I, and the slip frequency f.sub.2 and by calculating instantaneously T=I.sub.1. sup.2 F, where F is a function of f.sub.2 /R.sub.2, where R.sub.2 is the rotor resistance of the motor. The value of R.sub.2 is adjusted to match temperature by generally two alternative methods: (1) measuring the stator temperature, relying on the change of resistance R.sub.1, known experimentally, and applying an equivalent change for the rotor resistance R.sub.2 ; (2) by running the motor at rated speed and determining experimentally R.sub.2 /f.sub.2 as a function of F.