The invention relates to a powder supply system (1) for supplying a processing apparatus (2) with a granular substance (3). In this arrangement the powder supply system (1) includes a main container (4) and a powder conveying system (5) with a storage container (51) for conveying the granular substance (3) into the processing apparatus (2). In accordance with the invention, means (6, 611, 612, 62) are provided so that, in the operating state of the processing apparatus (2), a predetermined amount of the granular substance (3) can be conveyed from the main container (4) as working powder to the storage container (51) in such a way that at least a minimum amount (M1) is available as a granular substance (3) in the storage container (51).