Open-loop speed estimators design for online induction machine synchronous speed tracking

Open-loop speed estimators (OLSE) and closed loop speed estimators (observers) based on flux estimation are usually inaccurate since they depend on ill-known induction machine (IM) parameters such as stator winding resistance. This paper presents two methods to track accurately the IM synchronous speed over a large speed range with OLSE. An accurate adaptive integration algorithm (AAIA) developed for quasi exact flux position and magnitude estimation over a wide speed range is used. A current based speed estimator using AAIA, which is completely independent of the IM parameters, is introduced. The accuracy of two OLSE designs was tested on a fixed frequency network and with indirect rotor flux oriented control (IRFOC) of a squirrel cage IM. These techniques were simulated on a commercial package and tested experimentally on a 1/2 HP IM and on a 3 HP IM