KSB’s variable speed system for wastewater pumps

For a complete water column to be established during start-up, PumpDrive ramps the pump up to maximum speed within four seconds. This speed is maintained for three minutes so that an appropriate flow passes through all piping elements before the system starts its controlled, demand-driven operation. KSB says this ensures that the discharge line and pump casing are completely primed with the fluid to be handled.

The second new function is the so-called flushing function. The PID controller increases the speed up to a maximum value, which triggers the required flushing effect. The current control task is temporarily put on hold for this process. After the defined flushing period, the flushing function stops, and the system returns to its previous, controlled operation.

Flow velocity monitoring is another new feature. It ensures that the minimum flow velocities specified at the time of selection are met in order to keep the pipes free from deposits. The flow velocity is computed by the variable speed system based on measured electric values of the drive. No external sensors are required.

Up to six PumpDrives can be combined into a controlling unit via plug-in bus lines, which allows the user to operate six pumps in parallel. This unit starts and stops the pump sets in line with demand while ensuring that the operating load is distributed evenly. It compensates the failure of individual components without interrupting the operation. All PumpDrives for motors with ratings up to 55 kW have a harmonised design.

The PumpDrive variable speed system now features three new functions, especially created for operating wastewater pumps (© KSB Aktiengesellschaft, Frankenthal, Germany).