ABSTRACT
Induction motors operate on the principle of interaction of the stator magnetic rotating field on currents induced in the rotor winding. It can be a cage rotor winding, wound-rotor winding with slip rings or winding in the shape of high-current conducting sleeve, solid rotor coated with copper layer. The rotor windings are also contained in slots in a laminated core which is mounted on the shaft. In small motors, the rotor-lamination stack is pressed directly on the shaft. In larger machines, the core is mechanically connected to the shaft through a set of spokes called a “spider.” The cage-rotor winding consists of solid bars of conducting material which are positioned in the rotor slots. The core laminations for such rotors are stacked in a mold, which is then filled with molten aluminum. In this industrial process, the rotor bars, the end rings and the cooling-fan blades are all cast at the same time.
