Purpose: based on an in-depth analysis of the causes of damage to the insulating fingers of traction motors of electric locomotives, it is necessary to develop a method for increasing their operational reliability. The most effective way to obtain the desired result is to use an improved technology for restoring the electrical insulating varnish layer of insulating fingers using thermoradiation heating. The implementation of a promising technology in depot conditions is possible with the use of a chamber-type infrared heating unit, the control unit of which contains the most optimal energy supply mode determined during experimental studies on a laboratory combined heating unit. Methods: the most significant results of the work were obtained thanks to experimental studies of the electrical and mechanical strength of the cured electrical insulating varnish layer of insulating fingers, in addition, in the process of determining the optimal energy supply mode, finite element modeling methods of thermal processes were used. Results: a design of a laboratory combined infrared heating unit has been developed, thanks to which the optimal drying mode of insulating fingers has been determined, embedded in the operation of an industrial chamber-type unit for drying a set of insulating fingers. Also, the dependence of the breakdown voltage and the hardness of the outer surface of the insulating finger, linking its mechanical and dielectric properties, was determined. Practical significance: the results of the work can be used to improve existing technologies for depot and factory repair of insulating fingers, in particular, to create a series of industrial infrared heating units in locomotive service depots. It is also worth noting that the obtained curve of the dependence of hardness and breakdown voltage, in the future, will allow assessing the electrical strength of insulating fingers indirectly by the hardness parameter of the outer varnish layer.