The series RUVAC WS Roots vacuum pumps are driven by a air or water cooled canned motor. The available frequency converters have been matched to the pump so that the possibility of mechanically overloading it is excluded. In the case of a pressure difference which is too high, the rotational speed of the pump is automatically reduced until its load. Roots vacuum pumps of the series RUVAC WSU are provided with an additional integrated pressure equalization line and a differential pressure valve. Pumps from these series are supplied with a vertical pumping action as standard.