Method for manufacturing squirrel cage rotor

Abstract

Ceramic adhesive is applied inside the slots of an electric machine squirrel cage rotor prior to casting or insertion of rotor conductors. This heat-resistant insulation provides superior electrical insulation that is also mechanically rugged, thus enabling casting of squirrel cage rotors by die or cost-effective consumable pattern casting. The consumable pattern cast copper rotors are electrically well insulated, thus minimizing rotor losses. The ceramic insulation in cast rotors enables longer conductors to be cast by thermally insulating the molten metal from the cooler laminations. The ceramic insulation in fabricated rotors withstands the high temperatures of end ring attachment. This method is applicable to both conventional induction machine rotors and brushless doubly-fed induction machine rotors and provides the degree of electrical isolation of the bars from the laminations needed to avoid excessive parasitic torques in doubly-fed machines, while ensuring adequate thermal conductivity to dissipate conductive bar heat to the laminations.

Description

RELATED APPLICATIONS [0001] This application is based on a prior copending provisional application, Ser. No. 60 / 530,218, filed on Dec. 17, 2003, the benefit of the filing date of which is hereby claimed under 35 U.S.C. § 119(e).FIELD OF THE INVENTION [0002] The present invention generally pertains to squirrel cage rotors of electrical induction machines, including both conventional singly-fed induction machine rotors and brushless doubly-fed rotors, and more specifically, pertains to the use of a ceramic adhesive insulation that is applied on the interior surface of the slots during the manufacture of such rotors, prior to either the casting or insertion of rotor conductors within the slots. BACKGROUND OF THE INVENTION [0003] The rotor slot conductors of squirrel cage rotor electric machines must be electrically insulated from the steel lamination stack of the rotor to prevent stray electrical currents from leaking into the lamination stack. Such currents cause loss of efficiency an...

AI Technical Summary

Benefits of technology

[0016] The ceramic insulating coating comprises a binder and a ceramic powder, and the ceramic powder preferably includes at least one of an alumina, a berylia, a magnesia, a thoria, a zirconia, a zircon, a spinel, and a mullite powder. Most preferably the cerami

Problems solved by technology

However, none of these prior art insulation systems provides ideal insulation for high efficiency and minimum unbalanced pull, and none enables an effective consumable pattern casting of the conductors with copper.

Other prior art insulating systems for fabricated rotors either employ slot liners or use an insulating film that is applied to conductive bars that are then inserted into the slots; however, both of these approac

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