Motor Design Consulting Recommendations

[NIDinc]

We are a manufacturer looking to redesign an electric motor that we currently produce. It is a 2hp 3phase squirrel cage design and we are interested in something with 3-5 HP. Can anyone recommend a good consulting service or another good first step? We have been checking with a few lamination stamping companies to see of they have a stator die that could be adapted for our needs. Does anyone have a good resource for this?

 

[electricpete]

The following document the from Electric Power Research Institute discusses a range of issues to consider when uprating electric motors during rewind. Although I think it is primarily geared towards larger motors and is mostly geared towards uprates that do not involve a core change. But at least it's available for free (or for the cost of coughing up your email address).

ERPRI report 1009699 - Guide for Increasing the Capacity of Induction Motors



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(2B)+(2B)' ?

 

[NIDinc]

Thanks for that info. I'm not sure if their methods would work for us.

One other possibility would be for us to use our existing stator and rotor stamping and just create a longer stack length.
We might be able to increase the length 20%-50%. Are there other considerations when varying the length of an induction motor?
I realize inserting the windings would become more challenging.

 

[electricpete]

I'm not a motor designer.

Some thoughts fwiw (worth as much as you paid for it).

I assume you prefer not to increase the airgap. Then I would evaluate the stiffness of the rotor with longer distance between bearings does it still have the ability to resist rubbing the stator during start.

Longer machine can have different resonances which can cause a variety of problematic vibrations. Worst case, flexible rotor resonance makes rotor act flexible so more likely rotor/stator contact during running.

Perhaps you might need to upsize the cooling fans for the longer machine with more generated heat.

Often motors have some amount of internal endplay built in (NDE floating bearing) to allow for thermal growth. You need a little more internal endplay with a longer rotor.

Of course your equivalent circuit parameters are obviously going to change which potentially affects a lot of performance parameters .... per unit starting torque, per unit breakdown torque, per unit starting current, running power factor, running efficiency etc. Maybe that's already obvious. Changes to winding configuration (beyond just longer coils and bars) may be needed to keep the desired performance.

That's all I can think of. Maybe others have ideas.

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(2B)+(2B)' ?

 

[Hoxton123]

When all else fails, you have to engineer it!

 

[waross]

Are there other considerations when varying the length of an induction motor?

Frame size? You can't go much longer without going to a larger frame. For a 250% increase, consider a larger frame and increased diameter as well as increased core length. Two significant factors in performance will be the air gap and the profile of the squirrel cage bars.

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Ohm's law
Not just a good idea;
It's the LAW!