Background: A mathematical model of a squirrel-cage induction motor with inter-turn short-circuits in stator phases is presented in this paper. Material and methods: In the proposed mathematical model an extent and angular localization of short-circuit faults are determined using a simple form of short-circuit coefficient matrices. Presented mathematical model does not require any additional motor parameters than those that are required for conventional model of healthy induction motor. Results: The comparative results get through computer simulations and obtained from a laboratory test-stand with 2.2 kW squirrel-cage induction motor are contained in the article. Conclusions: The obtained results validate the proposed extended mathematical model of a squirrel-cage induction motor with inter-turn short-circuit of stator windings.