Motor efficiency degradation over time??
Motor efficiency degradation over time??
(OP)
Hello all,
I'm doing an energy cost analysis for a hatchery that uses multiple large (100-150 hp) pumps for the process flows. My question is this:
Can anyone tell me how much the efficiency of a motor decreases over time? These motors were installed in 1972. I figure the pump efficiency has dropped off quite significantly but I'm wondering about the motors as well.
2%...5%...???
Thanks,
Luke
I'm doing an energy cost analysis for a hatchery that uses multiple large (100-150 hp) pumps for the process flows. My question is this:
Can anyone tell me how much the efficiency of a motor decreases over time? These motors were installed in 1972. I figure the pump efficiency has dropped off quite significantly but I'm wondering about the motors as well.
2%...5%...???
Thanks,
Luke





RE: Motor efficiency degradation over time??
I presume you are asking about aging mechanisms. Here's my guess from largest likely changes:
1 - if the motor has been rewound during the period, then improper stripping of the windings at too-high temperature can damage the core interlaminaro insulation and increase core losses.
2 - If large ODP motor with filters and you haven't been changing the filters - temeprature will go up which increases I^2*R losses. Also very e2xcess dirt which blocks internal cooling passages of ODP motor.
3- Bearing packed full of grease may run hotter and less efficient. Bearing exposed to higher force from unbalance or misalignment may run hotter.
4 - Various non-ideal conditions such as unbalance and misalignment can lead to vibration which perhaps can decrease efficiency. But vibration shouldn't cost much energy by theory - it is exchange of energy between mass and spring stored energy without much energy dissipation, with energy loss only thru damping mechanisms.
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RE: Motor efficiency degradation over time??
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RE: Motor efficiency degradation over time??
I was hoping to get an idea about how much the motor efficiency might fall off. I was hoping someone has read a whitepaper or other article stating that a motor will lose such and such efficiency per year...
I know there are a lot of factors that could degrade the efficiency, but a range would be good.
-Luke
RE: Motor efficiency degradation over time??
http://www.easa.com/indus/rwstdy1203.pdf
The other changes are very small - no studies I know of although you might start with google. But again I don't think you'll find much there.
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RE: Motor efficiency degradation over time??
As for efficiency loss during rewinds, as a motor rewinder, I disagree with epete (may be for the first time). There are methods to strip windings without heating core. So the iron loss does not increase after rewind. On the other hand, we have the opportunity to use newer and better insulation for older motors rewinds, which almost gives leeway to pack more copper area thus leading to lower copper loss and higher efficiency.
Muthu
www.edison.co.in
RE: Motor efficiency degradation over time??
The really is no degradation curve such that you are looking for. Outside of physical damage and rewinding of the motors, the efficiency should remain mostly unchanged through out the motor's lifetime.
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: Motor efficiency degradation over time??
Good point that there is opportunity for improvements during rewind - for example newer insulation materials can allow more room for copper.
I also agree TurbineGen - we don't generally expect aging to cause any significant degradation in efficiency under identical conditions and the items I mentioned (other than improper stripping during rewind) will have very small effects - just listing the areas for consideration.
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RE: Motor efficiency degradation over time??
Not much changes with time in a motor. I suspect that the major cause of efficiency drop, when there is one, would be dirt and/or corrosion impeding the proper flow of cooling air. This is generally correctable.
Bill
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"Why not the best?"
Jimmy Carter
RE: Motor efficiency degradation over time??
Thanks again!
-Luke
RE: Motor efficiency degradation over time??
By the way guys, he said 1972, not 1992. Those motors are almost 40 years old. The difference in efficiency compared to a new design would be dramatic.
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RE: Motor efficiency degradation over time??
You're right - 1992 was a typo.
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor efficiency degradation over time??
Muthu
www.edison.co.in
RE: Motor efficiency degradation over time??
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Motor efficiency degradation over time??
RE: Motor efficiency degradation over time??
RE: Motor efficiency degradation over time??
Hi Ray & Sean.
And we want a motor repair forum pronto, or else, .....
we will filibuster (though Ray & I have already agreed to disagree recently).
Muthu
www.edison.co.in
RE: Motor efficiency degradation over time??
Bill
--------------------
"Why not the best?"
Jimmy Carter