This paper describes the unbalance and harmonics of voltage and current that are the causes of additional heating of the electrical machine. The principle of operation of the thermal imaging camera is explained and it is described how emissivity affects thermal imaging. The application of a thermal imaging camera in the maintenance of electric motor drives is described. During the field research in the stone wool factory, three induction machines of different power rating and loads are inspected using thermal imaging camera, and their thermal images are presented and discussed in this paper. The motor thermal limit curves, insulation classes, and protection devices such as bimetallic overload relay, thermistor protection relay and microprocessor thermal relay are analyzed. The motor thermal model algorithm which is used in microprocessor thermal relay is described. A PLC software for overload protection in which the motor thermal model and PTC thermistor protection is implemented. The PLC calculates the motor thermal capacity used based on the measured motor current, and measures the resistance of the PTC thermistors. The HMI interface displays the values of the thermal capacity used and the value of the measured motor current, as well as the buttons for starting and stopping the electrical machine. The control and supervision of the electric motor drive is realized with the PLC and its communication with the HMI interface, which together represent the SCADA system.