Method for operating a vacuum pump system and vacuum pump system applying such method

A method of operating a vacuum pump system, the method comprising the steps of:

• operating a primary vacuum pump comprising a variable speed motor;
• connecting at least two secondary vacuum pumps in parallel with said primary vacuum pump, each of the at least two secondary vacuum pumps comprising a motor;
• dividing the at least two secondary vacuum pumps in groups, each group comprising at least one of the secondary vacuum pumps;
• assigning at least a highest priority and a second highest priority for each of said groups;
• conducting a first measurement of an inlet pressure measured at an inlet of the vacuum pump system;
• comparing the first measured inlet pressure with a predetermined pressure value, and, if said first measured inlet pressure is higher than said predetermined pressure value, operating the at least one of the secondary vacuum pumps that is part of the group having the highest priority assigned to it;
• conducting a second measurement of the inlet pressure at the inlet of the vacuum pump system;
• comparing the second measured inlet pressure with said predetermined pressure value and, if, said second measured inlet pressure is higher than the predetermined pressure value, operating the at least one secondary vacuum pump that is part of the group having the second highest priority assigned to it,
• the method further comprising the step of starting said secondary vacuum pumps at a first predetermined startup vacuum load if the secondary vacuum pump comprises a fixed speed motor, or starting said secondary vacuum pump at a second predetermined startup vacuum load, if said secondary vacuum pump comprises a variable speed motor,
• wherein an assigned priority to each of said groups is based on one factor selected from the following group of factors:
• a price of electricity that powers the vacuum pump, an environmental condition of the vacuum pump, an accessibility of the vacuum pump for maintenance, and a wear on the vacuum pump.