Electrofriction method of manufacturing squirrel cage rotors
A method of making a squirrel cage rotor of copper material for use in AC or DC motors, includes forming a core with longitudinal slots, inserting bars of conductive material in the slots, with ends extending out of opposite ends of the core, and joining the end rings to the bars, wherein the conductive material of either the end rings or the bars is copper. Various methods of joining the end rings to the bars are disclosed including electrofriction welding, current pulse welding and brazing, transient liquid phase joining and casting. Pressure is also applied to the end rings to improve contact and reduce areas of small or uneven contact between the bar ends and the end rings. Rotors made with such methods are also disclosed.
1. A method of making a rotor for an electrical machine, the method comprising the steps of:
inserting conductors of conductive material in respective slots of a core with slots running longitudinally therein, the conductors extending longitudinally through the core and the conductors having ends extending out of an end of said core forming a discontinuous conductive surface at said core end:
pressing a continuous surface of an end ring of conductive material into contact with said discontinuous conductive surface;
joining said continuous surface of said end ring to the discontinuous conductive surface, wherein the conductive material of either the end ring or the conductors is aluminum or aluminum alloy; and
wherein the joining step includes applying torque to one of said surfaces in a oscillating bidirectional rotational direction to create friction and applying electrical current at the joint to create resistance heating.
2. The method of claim 1 , wherein the end rings are made of an aluminum material and the conductors are made of a copper material.
3. The method of claim 1 , wherein the end rings are made of a copper material end the conductors are made of an aluminum material.
4. The method of claim 1 , in which the conductor ends are tapered.
5. The method of claim 1 , in which a projection extends axially from said end ring continuous surface, wherein the pressing step includes pressing said projection into contact with said discontinuous surface, and the joining step further includes deforming said projection.
6. The method of claim 1 wherein said electrical current is direct current.
7. The method of claim 1 wherein said electrical current is alternating current.
8. The method of claim 1 wherein said electrical current is applied using a primary winding.
9. The method of claim 1 wherein said electrical current is applied using brushes.
10. The method of claim 1 wherein said electrical current is applied using leads.
11. The method of claim 1 wherein said torque and electrical current is applied simultaneously.
12. The method of claim 1 wherein said electrical current is applied intermittently.