AC MOTOR (REPLACE OR NOT)
AC MOTOR (REPLACE OR NOT)
(OP)
There is a 5,5kw motor for ventilation fan (2ways air blowing)- having a 7.3A consuption. What should be considered for having replace or not this motor with a smaler one? Reason:energy saving





RE: AC MOTOR (REPLACE OR NOT)
Gunnar Englund
www.gke.org
RE: AC MOTOR (REPLACE OR NOT)
RE: AC MOTOR (REPLACE OR NOT)
Also, to use the well used saying, if it's not broke then don't try and fix it. Mybe if you had a problem with the motor then yes, look at it but I would still have my doubts personally if it would really bring savings going smaller on such a (relatively) small motor.
RE: AC MOTOR (REPLACE OR NOT)
Full load or overloaded means worse efficiency (usually optimum at 3/4 load). So no reason to change.
If you need to reduce flow, then you can save energy. Yes. But that's another story.
Gunnar Englund
www.gke.org
RE: AC MOTOR (REPLACE OR NOT)
You pay the power company for the power that you use. This is the power to turn the fan plus the losses. If the smaller motor is turning the fan at the same speed, then the power required will be the same. The losses of a smaller motor may be higher than the losses of a larger motor running at part load.
A caveat; If you are considering changing from a low efficiency motor to a high efficiency motor, you may realise a saving.
However, I have found that the cost to change a motor or other equipment to a more economical unit invariably has such a long payback time as to be unrealistic.
As skogsgurra points out, this motor looks like it is well loaded. The next smaller size motor will probably be overloaded.
If you want to show a quick saving and you can live with slightly less air volume, then slow the fan down. This will give you an energy saving without changing the motor. I strongly suggest changing to a variable pitch pulley on the motor. Changing to the next smaller size of fixed pitch pulley may be too much reduction.
It depends.
respectfully
RE: AC MOTOR (REPLACE OR NOT)
The only thing I'll add is that if reduced flow is a possibility in your ventilator, then rather than replacing the motor you might also consider adding a VFD to it and a system to match flow to demand. That is a well proven energy saver, most VFD manufacturers will supply you with software to calculate your ROI.
Tangent alert! (based on waross' next-to-last comment)
The the people who gain the most by replacing working motors with energy efficient versions are the supplying utility. That is why many of them here in the US are offering rebates to users so they can better recover their investment in doing so. The users get a faster ROI on the change costs so the bean counters will approve it, the utilities get what they call an "avoided cost of delivery", a complex algorithm derived from not just the generating cost, but also the litigation expenses from needing to expand transmission capacity in a NIMBY environment. Not that the users don't save money, it's just that total Dollars saved actually favor the utilities more than the users. If a motor needs to be replaced for other reasons anyway, then by all means it favors the user.
For you non-native English speakers, NIMBY is short for "Not In My Back Yard" and describes the tendency for residents to oppose any additions of even changes to power distribution and transmission facilities based on fear of "radiation" and/or declining property values. It has become a big deal to utilities now.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: AC MOTOR (REPLACE OR NOT)
Gunnar Englund
www.gke.org
RE: AC MOTOR (REPLACE OR NOT)
Might I also point out that the worst of the damning "studies" on cancer from power line EM radiation have been propagated by your fellow countrymen? What's with you Swedes anyway? Mucking it up for the rest of us while you sit around in your wood-fired saunas I suppose
RE: AC MOTOR (REPLACE OR NOT)
I am a cynic brute, yes. But they are calling me a brute because I will not let them - not for the valid reasons.
Gunnar Englund
www.gke.org
RE: AC MOTOR (REPLACE OR NOT)
Rotten deviants... it's all their fault.
RE: AC MOTOR (REPLACE OR NOT)
BANANA's.
That would be: B-uild A-bsolutely N-othing A-nywhere
N-ear A-nyone
(sigh)
RE: AC MOTOR (REPLACE OR NOT)
Govt is getting stick for pending shortage of elect supply but can not build/expand current infrastructure because it might hurt a worm or affect the ecology. - cant have it both ways!!
Mark Empson
http://www.lmphotonics.com