A wide speed range induction motor drive based on electronic pole changing

The theory, modeling, analysis and control of an electronic pole changing induction motor drive are presented in this thesis. By independently controlling the different coil group currents in a three phase winding to alter the machine MMF spatial distribution, contactorless pole changing can be achieved. The electronic pole changing concept is applied in this research work to a three phase four pole induction machine fed from a six leg inverter. Four-pole operation is proposed from zero speed until the end of the constant power region. Employing contactorless pole changing to obtain two-pole operation extends the drive constant power region.;Due to the presence of six independent stator windings instead of three, the stator model and accompanying transformation are six dimensional. Based on the technique of vector space decomposition, the machine coupled circuit model is transformed to a reference frame model. As a result of this transformation, the coupled coil group variables are replaced by equivalent decoupled four pole and two pole dq0 variables. This reference frame model is utilized in analyzing the steady state and transient behavior of the proposed pole changing drive. A field oriented controller is also developed based on the reference frame model.;Experimental results of a prototype verify the anticipated drive capability curves and steady state performance. The transient associated with the pole changing transition is investigated using both digital simulations and experimental tests for different transition schemes. The machine non-linear magnetic behavior is analyzed with the aid of finite element analysis in both four pole and two pole modes of operation and the main flux saturation effect on the equivalent circuit inductance is quantified. Other possible contactorless pole changing drives are also briefly discussed with emphasis on the eight/four pole drive theory of operation and power capability conjecture.