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The Motors Blog is the place for conversation and discussion about gears all types of motors including AC motors; DC motors; servo, stepper and linear motors; and motor maintenance and efficiency. Here, you'll find everything from application ideas, to news and industry trends, to hot topics and cutting edge innovations. This blog is inspired by the Mechanical Power Transmission newsletter from GlobalSpec, which you can subscribe to here.

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4 comments

Do High-Efficiency Motors Save Energy?

Posted June 17, 2009 7:16 AM

Motor efficiency is not a single number; it depends on how the motor is used. Most efficiencies are measured at 75% output. What if the motor is used at 50% output? Or 90%? Or what if the load is highly variable? Part of the energy savings comes from reduced motor slip — but this actually raises the output speed, as well as the efficiency, and will increase the net energy in many types of loads. You may end up using more energy at higher efficiency! What is your experience?

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#1

Re: Do High-Efficiency Motors Save Energy?

06/17/2009 9:53 PM

Yes if installed correctly, Type, HP, service factor,temp rise, PF, then load match.

over an uncorrectly design one . mis size etc.

But note Eff,Pf, phases, and Voltage have nothing to do with determining the output watts of a motor

Eff = Output power (w) / Input power (w) ExI = w

since motor out put is in HP its 746 w per HP

not counting the Power Losses IxIxR = PL

conductor resistance, flux leakage, eddy currents and hysteresis losses

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#2

Re: Do High-Efficiency Motors Save Energy?

06/18/2009 7:45 AM

You have hit upon a fine point. The motor may be highly efficient but the system that was designed around it may take away the original efficiency. Which is why the entire system should be designed for a specific, efficient task, not just a single entity.

Yet we suffer from the fools around us who constantly insist that to reduce energy we simply have to replace or use a single device in an inefficient system.

Due to the terms of my parole, I have to stop writing now before I go into my politico manifesto. So I will spare you my (now up to) thousand page rant.

Guru
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#3

Re: Do High-Efficiency Motors Save Energy?

06/18/2009 10:55 AM

If high efficiency motors are used in conjunction with electronic efficiency controllers both single and three phase. These controls are an improvement on " Nola Energy Saving Technology"

It is is a very good system for motors which have to work with variable loads where it can adjust the efficiency to suite the load instantaneously it gives a cost saving on power consumption which is worth while. Motors which are designed to run on continuous loads which are designed for that load would not see much if any great power saving apart from varying mains voltage input.

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#4

Re: Do High-Efficiency Motors Save Energy?

07/23/2009 11:14 AM

Yes, they do save energy .The question should be : Are premium efficiency motors worth the price ? Well, it depends on how long they are operating . For assured energy saving always use variable speed with variable speed drive in lieu of a starter .

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