A power supply apparatus for a shaping machine includes an intermediate circuit to be connected to at least one drive of the shaping machine, a power supply mains, and a power storage device. A measuring device measures an electric voltage or an electric current at the intermediate circuit, and a closed-loop regulating device regulates a power transfer between the power supply mains and the intermediate circuit based on the measured voltage or the measured current. The closed-loop regulating device can increase a main power furnished by the power supply main to the intermediate circuit if the measured voltage or the measured current leaves a first range, and can reduce the main power if the measured voltage or the measured current passes into a second range, the second range being smaller than the first range and completely contained in the first range.