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Ok ok ok ok... I think I've got it! Please let this be the answer. 1) Power = VI = Torque x RPM 2) When you throttle a pump, as sethoflagos stated, the impeller still spins but it has to accelerate a smaller volume of fluid. F = ma. Mass goes down so force goes down, so current decreases as...

The power consumed by the pump increases and this is directly proportional to the relative density/specific gravity of the liquid being pumped. The relationship between the flow through the system and the system resistance is given by: h = KQ² h = head loss in metres K = constant Q = flow...

I will use this thread to post those beautiful motor truths as I come across them. This one helps me to understand the high current drawn when a pump is started. In a motor a coil carries current in a magnetic field. As the coil rotates in the magnetic field, a back emf is generated that tend...

Good work everybody. Now I will task you further. You all seem to have an intuitive understanding of what will happen. Ten points to the one who can tell me why. 1) JJ Pellin: Why does Less Flow = Less Torque as you state. I thought Torque was the Force of the impeller times the radius. Should...

Thanks again. Now I know how the power consumption of a pump will vary for different operating regimes. I must admit that I'm still a little fuzzy on the why. Why exactly does a pump motor draw a lot of current at startup then the current draw falls off? Also, I appreciate that the current and...

Hey, Thanks for answering my question Crowley. Though I understand your answer , I feel it's not the full story. It is true that through throttling the power consumption will decrease per the mechanical equation Power = torque x rpm. As you say, flow drops way more than head increases. My...

Hello, I am trying to figure out what happens to electrical power consumption for a centrifugal pump when one throttles a downstream valve. Mechanical Power = Torque x RPM Electrical Power = V x I My understanding is that when you throttle downstream to reduce the flow you create backpressure...