Supercharger motor system for a motor vehicle, comprising: an
internal combustion engine, a small-capacity, variable-geometry
turbocharger designed to meet the charge air requirement up to a predefined supply value, and an electrically driven compressor arranged in parallel to the
turbocharger, which is operated by an
electronic control unit, wherein the engine is configured to receive a primary supply of charge air during normal engine operation below the predefined supply value from the
turbocharger and to receive an additional supply of charge air from the electrically driven compressor when it is necessary to meet a temporary high demand for charge air above the predefined supply value, and a recirculation circuit to build up pressure when the electrically driven compressor starts up before the electrically driven compressor is connected to the engine, wherein the recirculation circuit includes an electrically controlled recirculation valve for directing the
airflow through a duct connecting an outlet of the electrically driven compressor to an inlet of the electrically driven compressor.an electrically controlled shut-off valve positioned between the outlet of the electrically operated compressor and the motor for selectively isolating the outlet of the electrically operated compressor from the motor, and a non-return valve to prevent
backflow of air from the inlet of the electrically operated compressor into the
atmosphere, wherein the
electronic control unit is configured to , Keeping the electrically controlled return valve open and the electrically controlled shut-off valve closed when the electrically operated compressor starts up, until the pressure in the return circuit reaches a predefined
limit value, and in response to reaching the predefined
limit value, opening the electrically controlled shut-off valve and closing the electrically controlled return valve.