In order to avoid destruction of braking chopper IGBTs, the need of information about instantaneous junction temperature arises. As the operation regime is transient, there is interest of having developed a technique that will allow wind turbine inverter manufacturers to limit the number of paralleled transistors as much as possible, while avoiding physical destruction and keeping the ability of fault ride-through for same period of time. This project proposes a novel electro-thermal model for the braking chopper used in wind turbine converters. The thermal model is realized as a ladder network, for better accuracy. Using thermal information provided by it, the model is developed to emulate dynamic changes in collector-emitter voltage drop. A test setup is proposed in order to reproduce the operating conditions of a braking chopper used in a real field wind turbine application. Electrical devices dimensioning, cooling system design, control and measurement PCBs design are necessary for the setup. The control PCB is designed by taking into consideration that the system must be self-protective. As final purpose, a simple and accurate estimator for junction temperature is realized and presented. The main advantage of the estimator is that it uses only electric measurements – collector current and collector-emitter voltage drop.