In the middle of 1887, the physicist Tesla designed and manufactured a first prototype of a motor with significantly reduced size of the biphasic induction motor, constituted by the short-circuit rotor. These engines also had a low yield. However, it impressed in a way that the US company Westinghouse bought the patent for a million dollars, and signed the agreement to pay a dollar for each machine that came to project in the future. However, the significantly reduced performance of this machine made its projection economically impossible, causing some years later, the searches were aborted.
Thus, electrical engineer Dobrowolsky of the company AEG, based in Berlin, insisting on the research of the AC motor has filed the patent application for a three-phase motor with cage rotor. The machine presented achieved a power of over fifty watts, an average yield of 80% over the power consumed and an excellent starting torque. The advantages of the cage-rotor engine compared to the direct current were expressive, with a simplified construction, quiet, reduced maintenance and great safety in operation. https://www.mrosupply.com/bearings/mounted-bearings/bearing-inserts/2256970_ar-3-112_sealmaster/