What happen when slip ring induction motor overloaded?

Let me give you a different yet convincing answer, as you over load the machine, it will run slow to get more induced emf in rotor, we all agree to a point that,as it slows down it will have more emf but as the electrical angle increases beyond 90, for slipring machine with no automatically induced poles unlike cage rotor, this deter the flux bonding between stator and rotor , As already loaded , this is a cumulative action there by machine stalls,

Do let me know if you need further explanation.