VFD efficiency pump application
VFD efficiency pump application
(OP)
For a given flow rate is it more efficient to run one VFD controlled pump at 90 percent or two VFD controlled pumps at 45 percent?
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VFD efficiency pump application
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RE: VFD efficiency pump application
Assuming that you most likely mean speed, then probably run one motor at 90% speed. To really know the answer you would have to plot the pump efficiency curves against the motor / drive efficiency curves, but my but feeling says that single pump will win. The pump likely was sized for optimum efficiency closer to the top of it's curve rather than the bottom (most pump curves dont go below some point anyway, so 45% is closer to the bottom, not the middle). Then the added motor losses from having to energize a second machine, plus the added mechanical friction, windage and copper losses in that machine will push it way over the edge of being lower efficiency than just one pump.
But to this, you have to factor in redundancy. One pump may be more efficient, but if it fails and it was all by itself, your efficiency goes to hell in a hand basket doesn't it?!
"Will work for (the memory of) salami"
RE: VFD efficiency pump application
RE: VFD efficiency pump application
RE: VFD efficiency pump application
squeeky, with variable flow pumping, the operating point generally follows system curve and not pump curve. So, that data is redundant in most cases.
RE: VFD efficiency pump application
RE: VFD efficiency pump application
The link worked for me. We are not using VFDs for filling applications, but good to know why.
KRAkid
RE: VFD efficiency pump application
The crux of their argument lies in this statement:
VFDs are for flow control ergo their premise, as applied to the smaller subset of pumping applications that do NOT involve real-time flow control, is accurate. But "increasing evidence"? What the heck does that mean?
Also, this line of "marketing rationalization" is like that which decries how much more energy efficient trains are compared to trucks, as measured by energy consumed per unit of payload. Perfectly good argument, but only as long as your destination has train tracks going to it...
"Will work for (the memory of) salami"
RE: VFD efficiency pump application
Squeeky - the pumps would be the same size, not 1 large pump vs 2 half-sized pumps.
I would also expect that running 1 pump near full flow capacity is the more efficient way to operate.
As for the paper. There are many VFD manufacturers who give the example of changing from cyclic filling to continuous filling as a way to save energy.