Increasing The Frequency (RPM) For Well Pump

From: Pump Affinity Laws - Engineering ToolBox

Note! If the speed of a pump is increased with 10%

• the volume flow increases with 10%
• the head increases with 21%
• the power increases with 33 %

nick name has replied well.

You have seen the pump curves. For the particular manufacturer you are takling, you just check, he must have shown the increas in flow at contant head. The resistance in form of head is kept contant, so you will get increased flow from the pump drawing water from the well and discharging in the fixed tank at constant height with increase in frequency or RPM.

As soon as you increase the head resistance, the increase in coresponding flow will reduce at increased head.

Variation of head and flow with respect to rpm will depend on pump type and impeller/ scroll design. Some cases variation will be steep and some cases curve will be flat. Fan law will be applicable in all the cases at constant system resistance. increase in flow and head are interchangeable by varying system resistance.

For example, just consider a well pump discharging to atmosphere. By increasing rpm flow increases according to fan law. You may be thinking that the head is same but is is not so, it will reflect in the form of increased velocity head. If you install a valve at the outlet to restrict the flow as previous (at lower rpm), then head will increase significantly (can be measured as discharge pressure).

your answer is in the Laws of Affinity. If you don't want to increase the head value then why look at increasing the Hz??

To be honest unless I've missed something here I think your question is pointless, however I'm open to being corrected and educated as to your intentions and what you really want to learn.