Study On The Pole-changing Wound-rotor Asynchronous Machine While Bridge-rectifiers Are Used To Convert The Rotor Current From AC To DC

This paper presents a new technique of pole-changing wound-rotor asynchronousmachine for speed adjusting. A new system is studied and analyzed while bridge rectifiersare used for pole-changing wound-rotor to convert the current from AC to DC and rheostatsare connected in series in order to adjust speed .The general regulation of the connectingmethods of rotor windings is studied and analyzed. A mathematical model is set up forcomputing and simulating, some important equations are deduced, while a sample machineis produced for testing. For general pole-changing motor, if use squirrel cage in rotor, we can't adjust speed byexternal rheostats. If wound-rotor used, sometimes, we can adjust speed in onepole-number by external rheostats but can't in another one. And, sometimes, we can adjustspeed in both two pole-numbers by external rheostats but a lot of slip-rings and complexswitches needed. When bridge rectifiers are used to convert the current from AC to DC forWound-rotor, it's speed can be adjusted in big range just like a general pole-changing motorand the speed can be adjusted precisely just like an ordinary wound-rotor motor, and it canshift from one number of poles to another smoothly with external rheostats in series in bothtwo pole-numbers. And, usually, the winding coefficient of rotor, the performance andapplicability of the motor will be improved, too. The new speed-adjusting technique studied by this paper have a lot of advantages,such as higher efficiency for the motor, wider range and more precisely for speed adjusting,simpleness of mechanism structure, etc.