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ENERGY EFFICIENT INDUCTION MOTORS


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#1 dipitmehta

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Posted 09 February 2006 - 05:55 AM

hi,
i need anykind of help on "ENERGY EFFICIENT INDUCTION MOTORS".

is it true that these kind of motors are different form conventional INDUCTION MOTORS and if true, what is the difference between the "CONVENTIONAL INDUCTION MOTORS" and "ENERGY EFFICIENT INDUCTION MOTORS"?

#2 marke

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Posted 09 February 2006 - 06:32 AM

Hello dipdtmehta

Welcome to the forum.
The enefgy efficient induction motors are just a development of the standard induction motor. The design has been optimised for low slip, low copper loss and low iron loss.

One of the areas of change is in the rotor where the bars are a shallower bar with a lower resistance. The energy efficient motors have a tendency towards a higher start current than a stadard induction motor.

Best regards,

#3 jraef

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Posted 09 February 2006 - 06:50 PM

I just finished a course on this subject, so you can benefit from my notes.

Not all motor manufacturers use exactly the same methods of increasing efficiency. There are several areas of improvement , which all come with compromises in some other way. Each motor manufacturer uses their own combination of methods to try to provide an optimized solution. In order of importance to overall loss reduction, they are (expressed in percentage of total losses):

Stator copper losses (35%), which can be improved on by increasing the number of stator slots and the cross sectional area of the winding conductors.

Rotor copper losses (25%), which can be improved by the method Marke described above, or by actually increasing the cross sectional area of the rotor bars and improving the joint between the bars and the end ring.

Core losses (25%) from hysteresis and eddy currents in the lamentations, which can be improved on in a number of ways such as using better quality steel, more thinner lamentations, reduced air gap and using a longer core.

Windage and bearing losses (5%), which can be improved by using better cast iron frames so that they can tolerate less cooling fan air movement, hence smaller more efficient fans, and better quality bearings and manufacturing tolerances to reduce friction and vibration.

The last 10% of losses are stray load losses caused by leakage flux induced by load current fluctuations. These vary as the square of the load and are difficult to measure or reduce.

So 85% of the total losses in a motor can be reduced, but not by 85% obviously because you can never have zero losses. In addition, each of those methods incurs some other consequence such as increased cost, increased magnetization current (instantaneous inrush), lower locked rotor torque, increased size and weight etc. etc.

Hope that helped. If this was for a homework assignment, let me know if I got a good grade!
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#4 marke

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Posted 09 February 2006 - 07:21 PM

Hi jraef

Sounds like an interesting course. Howcome you get to go on all these courses?? no such thing down here.

Best regards,

#5 jraef

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Posted 10 February 2006 - 07:02 AM

Someone was offering it and I signed up. Energy efficiency is a big deal here in California, grant money is available for people to teach energy savings topics. Lots of opportunities to learn, but most of the seminars are for things I am not interested in. Even though I am not in the motor designing business, I thought it would be good to know so I went for this one. I was right. It shed some light on a number of things I already heard but didn't know for sure.

Part of the reason why we have so much available locally may be because this outfit is headquartered here in the SF Bay Area, the Electric Power Research Institute. It's mainly geared towards the power generation industry, but they sponsor a lot of energy efficiency stuff as well.

http://my.epri.com/
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