Squirrel cage rotor

The squirrel-cage rotor shown in photograph (a) is referred to as an “open-slot type.” A conductor, which has a cage-like structure, is contained in the iron core. It is quite unusual, as it uses brass rods and rings instead of the more usual aluminum die casting. In photo (b) the iron core has been chemically dissolved and only the aluminum remains.
Photo (c) shows a punched silicon steel sheet used in both open- and closed-slot type iron cores.