Promotion paper theme is "Investigation and development of diagnostic methods and equipment for electrical inductor coil windings insulation". Paper consists from 131 pages, 104 pictures, 1 table, 1 attachment, 114 literature sources. Here is investigated existing winding insulation diagnostic methods, their principles, use and limited opportunities in this paper. Is invented new insulation diagnostic method on basis of resonant inverter half bridge scheme. In analytic part is invented and analyzed insulation method. It is compared with existing diagnostic methods. There are mentioned cases when this method is recommended to use. Also have shown benefits in relation to other methods. In paper calculation part is developed methodology for choice of parameters for various coils and their limited work options. Are investigated processes in insulation damage case and have found opportunity to detect it more effective and faster than previously mentioned methods. In this paper have developed method with bench coil. In this case this method is more effective. In paper experimental part are made experiments with coil. Have been checked methods conformity to theoretical basis. Acquired results have been compared with results from computer simulations and calculations. Have been made conclusions about method conformity to paper tasks.