Patent ID: 6121748
Filing Date: 2000-09-19
Classification: H02P,Y02P

Abstract:
A controlling method for an inverter controlled induction motor wherein the slip of said induction motor is detected and the optimum slip S .eta..sub.MAX dependent on the constant of said induction motor and the frequency supplied to said induction motor providing the highest efficiency is calculated by the following formula;S.eta..sub.MAX =r.sub.2 /Lm[r.sub.m /2/.pi./(r.sub.1 +r.sub.2)].sup.1/2 /(f.sub.0).sup.1/2where r.sub.1 is the primary resistance of said induction motor,r.sub.2 is the secondary resistance of said induction motor,Lm is the excitation inductance of said induction motor,r.sub.m is the iron loss resistance of said induction motor, andf.sub.0 is the supply frequency to said induction motor, the optimum slip and the slip of said induction motor are compared to determine a voltage manipulated variable which is used to form an output voltage and magnetic flux instruction for running said induction motor at the slip which provides the highest efficiency.