Today’s water industry VSDs come packed with smart functions as standard and can add several percent to the efficiency of pumping equipment and cut maintenance. Yet many VSD users only use a small proportion – if any – of these functions. The reason is that there is a lack of understanding about what these functions do and the benefits they bring.
Smart functions bring both capital and operation benefits. By putting control functions in the drive, it cuts the need for a PLC, at the same time helping to save energy, reduce downtime and prevent pump jamming and pipeline blocking.
Among the intelligent pump functions is sleep boost, which runs the pumps to boost the pressure or water level just before they shut down, extending the pump’s sleep time and so saving energy. It also avoids unnecessary starting and stopping of the pumps.
Another function is pump priority control, which is used to balance the operating time of all the pumps in the system. It can be a great help in planning maintenance and can boost energy efficiency by operating pumps near their best efficiency point – in a system where the consumption rate is greater during the day, the drive can be programmed to operate higher capacity pumps during daytime and smaller units at night.
The pump cleaning function, also referred to as anti-ragging, is the smart function most commonly used by the water industry. The standard way of detecting flow problems is to react if the pump is drawing a higher than normal current or torque as it tries to deal with the extra load. This method of detection is not always reliable and can be too late as the blockage has already reached a critical stage and cannot be undone easily.
However, the pump cleaning function takes action before things get critical. When a blockage is detected, the drive automatically runs the pump back and forward rapidly to clean the impeller, quickly returning flow rates to their normal level and avoiding any reduction in service. This also avoids the needs for more costly intervention, such as lifting the pump to remove the blockage.
Smart functions enable the VSD to sweat the other assets in the pump system – in other words make them work harder and/or better. For example, the pump cleaning function doesn’t benefit the drive itself, but it can extend the life of the pump, reduce maintenance intervals and increase efficiency of the pump system as a whole