The high-voltage converter with the input voltage of 3000 V DC is considered for use as a power supply for auxiliary circuits of commuter electric trains and passenger cars that are used on Russian railways. The limitations on the use of semiconductor devices in converters with an input voltage of 3000 V are shown. The power electrical circuits of the input units of the considered high-voltage converters are shown when using of 1700 and 6500 V IGBT. The expressions for calculating the power losses and the algorithm for selecting the switching frequency of 6500 in IGBT are given. This article is of interest to developers of high-voltage DC converters with an input voltage of 3000 V and higher, which choose IGBT for the power circuit of input units with using the high frequency principle of the electrical energy transformation.