What is the purpose of a variable speed drive?
All systems require a means of flow control. The plant’s output requirements may change causing flow demand to vary and therefore the various systems throughout the process must be able to modify their output flow rate. To achieve this, pumps are sized for the maximum anticipated flow rate. The most frequent means of reducing the output flow rate is to have a line which re-circulates flow back to the suction tank. Another method is to have a valve in the discharge line which reduces the output flow rate when throttled. Either method works well, but there is a penalty to be paid in consumption of extra power for running a system, which is oversized for the normal demand flow rate. A solution to this power waste is to use an electronic variable speed drive. For a new installation this alternative should be considered. This provides the same flow control as a valved system without energy waste. What is Total Head? Total Head is the difference between the head at the discharge vs. the head
