9510115 Lipo A frequent requirement in motor drive applications such as spindle drives, steel plants, and paper making machinery is to operate at constant poser over a wide speed range. Constant power operation is particularly important in the field of electric traction which covers a wide range of applications ranging from locomotives to electric vehicles. At present, field weakening techniques are used to widen the speed range of ac machines of conventional design, but as the desired speed range for constant power operation increases beyond twice the normal (or "rated") speed, the motor size and weight increases dramatically for both induction and permanent magnet type machines. In the proposed project, a comprehensive analytical, simulation, design and experimental program is set forth to develop ac induction and synchronous machines which possess the capability of an extended "constant power" field weakening range without need for an oversized machine. Pole changing of the stator winding of both types of machines is accomplished by proper control of the currents fed to the phases of a specially designed stator winding using only conventional pulse width modulated inverters. Hence, the stator pole changing mechanism does not necessarily introduce any additional switches, contractors or solid state (or passive) components to achieve its task. The goal of achieving extended field weakening range will be accomplished by means of innovative concepts of stator and rotor design which will enable these new machines to be roughly 30 to 50% the size and weight of conventional ac machines presently used for this same purpose. ***
