The safety and reliability requirements are becoming more and more strict in a number of applications, such as automotive, aerospace and ship propulsion. The canonical models of electric motor drives are developed assuming a healthy condition of the machine, and tend to fail when simulating a fault transient. Therefore, the transient current and torque occurring in case of fault are often hardly estimated and predicted. For this reason, this thesis focuses on developing an accurate simulation model of the motor drives, capable of dynamically covering faulty conditions. This permits to better understanding of the fault dynamics, verifying the motor design, and developing effective control strategies for fault detection and reaction.