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Originally Posted by freeloadingbum
Back on topic: Cathar, how did you arrive at the 50 to 60% figure for pump motors? I had read in another thread where myv65 said motor efficiency was around 75 to 85%. Is there something different with regards to pump motors that decreases it to your value, or was myv65 just wrong?
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Hmmm, when it comes to pumps I would always defer to Dave (myv65) over myself.
I got those ratios from browsing through the Iwaki catalog and looking at their mag drive pump motor output vs motor input ratios. Mind you, I'm talking mag-drive motors, and myv65 is probably talking direct-drive motors. It may be possible to get a 75-85% efficient mag-drive, but I doubt it, or at least Iwaki can't achieve it and mag-drive pumps don't come much better than the Iwaki's (plenty of makers around about the same level of efficiency though).
Edit: Some of the larger Iwaki mag-drive do appear to get to 70% efficient, but we're talking 100W+ motors here, not 10-30W mag-drive motors. All Iwaki motors below 100W or so see a fairly large drop off in efficiency, with the smallest models being just 15% efficient.
My guess is that it becomes extremely hard to make efficient mag-drive motors once you get down to the levels we want (<50W).