VSD, ASD, VFD Energy Savings? 2
VSD, ASD, VFD Energy Savings? 2
(OP)
This is a continuation of a discussion from this link;
http://www .eng-tips. com/viewth read.cfm?q id=260203& amp;page=1
BigInch, the curve you pasted is typical. The efficiency is best only between 425 and 375 GPM, even with varying head. This is a very narrow margin to be working with, and anything below 375 GPM is losing efficiency. I made a curve of a similar pump with efficiency curves at the minimum and maximum speed. As you can see the efficiency and horse power curves are very close together. I only see the efficiency track the speed for about the top 10% of the flow rate. So from 0 to 90% flow, a VFD is wasting or burning energy, even when possible to reduce the head required. The green line is my interpretation of the actual horse power as the RPM varies.
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BigInch, the curve you pasted is typical. The efficiency is best only between 425 and 375 GPM, even with varying head. This is a very narrow margin to be working with, and anything below 375 GPM is losing efficiency. I made a curve of a similar pump with efficiency curves at the minimum and maximum speed. As you can see the efficiency and horse power curves are very close together. I only see the efficiency track the speed for about the top 10% of the flow rate. So from 0 to 90% flow, a VFD is wasting or burning energy, even when possible to reduce the head required. The green line is my interpretation of the actual horse power as the RPM varies.





RE: VSD, ASD, VFD Energy Savings? 2
RE: VSD, ASD, VFD Energy Savings? 2
I take it that your efficiency values at the right of the graph are for 100% speed (3450 rpm), so your efficiency at 2900 rpm and 370 gpm is,
adjusting that 370 gpm @ 2900 rpm to a flow at 100% speed (3450 rpm),
Q100 = 370 gpm / 2900 * 3450 = 440 gpm
looking at efficiency for the adjusted flow Q100 = 440 gpm gives about 63%
That's only 1% difference in efficiency when changing from 3450 to 2900 rpm.
Yes, we know that a VFD won't work well with your 85% minimum speed for maintaining minimum head, so I'm not surprized.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: VSD, ASD, VFD Energy Savings? 2
RE: VSD, ASD, VFD Energy Savings? 2
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