A variable speed drive (VSD) is a digital controller that regulates the rotational speed of a motor. It enables the pumping speed of a vacuum pump to be adapted exactly to the actual requirements of your process. The result: significant energy savings. Busch Vacuum Solutions offers a wide range of vacuum pumps with integrated VSD. Even vacuum pumps that have already been installed can be easily converted with retrofit kits.

Fluctuations in vacuum demand

Vacuum demand often varies within production processes. Ideally, the vacuum supply should be synchronized with demand. With a variable speed drive, vacuum pumps can be adjusted to match variations in vacuum demand. Reacting to fluctuations in demand makes considerable energy savings possible. In combination with a pressure sensor, a variable speed drive automatically regulates the rotational speed of the pump’s motor.

Choice of operating modes

In scenarios with changing process parameters, we recommend vacuum pumps that can be controlled on a demand-driven basis and that either guarantee a consistent pumping speed or constantly maintain the required vacuum level. For processes with constant vacuum demand, it is recommended to leave the vacuum pump running at constant speed. For processes with changing vacuum demand over time, the pressure control mode is the ideal choice. In this case, the vacuum pump adjusts the rotational speed according to the required vacuum level. Once this vacuum level has been achieved, the vacuum pump continues to run at minimum speed, enabling it to respond to a sudden need for increased vacuum demand. This makes it possible to achieve additional energy savings.

Cost savings and improved performance

With a vacuum pump such as the R5 rotary vane vacuum pump from Busch, the integration of a VSD allows for energy savings of up to 50 percent. In a typical production process using a pump with a 30 kW motor, this results in a CO₂ savings of more than 10,000 kilograms annually – an amount that more than 1,000 trees would absorb. Maintenance costs are also reduced as compared to fixed speed pumps, due to lower average usage that limits wear on bearings and seals. In addition, a motor with VSD can be operated at a higher speed independently of the power supply. This results in a pump speed increase of around 20–40% and a correspondingly higher pumping speed than when the pump is operated at 50 Hz.