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#79830 01/30/02 09:57 AM
Joined: Aug 2001
Posts: 31
C
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The rated full load speed is always listed on a standard 3-phase induction motor in RPM.

The question is where does one find the maximum rpm possible for a motor? Is it from the manufacturer only? There is no ref. in NEMA mg1 on this particular subject that I remember.

Is it more a function of insulation rating or mechanical transmission I.E. bearing life?

Carl


Carl Lee Tolbert
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Joined: Mar 2001
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Are you wondering about the maximum speed that would be allowed if operated by a VFD? Otherwise, how would you increase the speed
(beyond the theoretical speed minus slip?)

Joined: Aug 2001
Posts: 31
C
Member
Yes, sorry....If someone wanted to run the max of a 4 pole motor at 3000 rpm.

Carl


Carl Lee Tolbert
Technical Support
AC Drives
Automationdirect.com
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What is your application? How big & fancy is the motor? This question came up in one of our drive applications. I couldn't get a firm maximum RPM value from our rep. He said you can overspeed them somewhat, but you lose HP. I would call the motor manufacturer to get an answer. If you are going to regularly operate in the 3000 RPM range, you should probably get a 3600 RPM motor and control that instead.

Joined: Aug 2001
Posts: 31
C
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It's not a question dealing with a specific application.

Is it something a motor mfg. can only answer (like you said calling the company)?

I was looking for documentation or information that elaborated on the concept of over-driving standard 3 phase motors. With reference to nameplate data and NEC 430.

I really appreciate your help Redsy.

Carl

*******************************************
[Linked Image]

A friend of mine found the information I was looking for. It was in NEMA MG-1. There is no reference in NEC for this motor information. The image is a screen capture of the appropriate page.

Thanks,
Carl

(picture inserted into thread)

[This message has been edited by Webmaster (edited 01-31-2002).]


Carl Lee Tolbert
Technical Support
AC Drives
Automationdirect.com
Your source for the most practical automation products at almost-free pricing, delivered by 11 a.m., just by clicking a mouse.
PH: (770)844-4200
Fax:(770)886-3199
www.automationdirect.com
Joined: Aug 2001
Posts: 31
C
Member
12.53.1 is the applicable clause. It's a pain sometimes weeding through the information.

Thanks everyone.

Carl


Carl Lee Tolbert
Technical Support
AC Drives
Automationdirect.com
Your source for the most practical automation products at almost-free pricing, delivered by 11 a.m., just by clicking a mouse.
PH: (770)844-4200
Fax:(770)886-3199
www.automationdirect.com
Joined: Mar 2001
Posts: 2,056
R
Member
Carl,
Is the table shown actually 12-4A, or is that shown elsewhere?

[This message has been edited by Redsy (edited 02-01-2002).]


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