I think, Don Miguel, you meant the relation between water hp [WHP] or brake horse power [BHP] and number of stage of a multi-stage centrifugal pump.
This is related to Centrifugal Pump Theory and not to Electrical Motor and Drive.
I don't intend to fight the wind mills and to develop here such theory, but what I know about the multi-stage centrifugal pumps it is the fact that for a certain liquid flow the head will increase direct-proportionally [approximately].So the power also will increase proportionally.
Best Regards
