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#80179 - 03/12/02 03:28 PM Overcurrent Protection
Joe Tedesco Offline

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
What types of overcurrent devices do you install to protect motor circuits?

Do you have any comments about fuses or circuit breakers?

[This message has been edited by Joe Tedesco (edited 03-13-2002).]
Joe Tedesco, NEC Consultant

2014 / 2011 NEC & Related Books and Study Guides
#80180 - 03/13/02 08:27 AM Re: Overcurrent Protection
Joe Tedesco Offline

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
What is a design E motor, and required overcurrent protection for one?
Joe Tedesco, NEC Consultant

#80181 - 03/13/02 05:17 PM Re: Overcurrent Protection
dana1028 Offline

Registered: 01/09/02
Posts: 163
Loc: San Carlos, CA
Design E motors - in my motor class this was discussed last week...they said this is an example of the code getting ahead of technology...kind of...a few years ago there was talk of developing these super efficient (E) motors...turned out these motors were so expensive to develope no one wanted to buy such motors are on the market.

#80182 - 03/13/02 06:10 PM Re: Overcurrent Protection
Ron Offline

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
I like to use a motor circuit protector (aka MCP or cirucit breaker with instantaneous only) with a solid state overload. This allows for the most flexibility and ease of maintenance.

Although manufacturers like Baldor have made Super E - Premium efficiency motors, I believe they are still Design B. Design letter indicating the shape of the tourque speed curve characteristics.

#80183 - 03/13/02 10:09 PM Re: Overcurrent Protection
ElectricAL Offline

Registered: 10/10/01
Posts: 615
Loc: Minneapolis, MN USA

As I recall, the Design E NEMA spec was rescinded. . .about a year ago. I read it in a trade journal (can't find the one right now) and heard it from a State Electrical Inspector who was leading a Code Class, February, last year.

Al Hildenbrand

#80184 - 03/14/02 04:22 AM Re: Overcurrent Protection
ctolbert Offline

Registered: 08/09/01
Posts: 33
Loc: Cumming, GA USA
To comment on the first question:

The thing I deal with everyday is the use of IEC starters and the MSP (motor starter protector).

The reason I bring this up, the MSP does not meet UL 489. Which means that it cannot be used as a stand alone SSPD (short circuit protective device.) In Europe, it is recognized as such. It's really confusing.

It can be used in the context of NEC 430-53c which is group motor rating. However, I get at least 10 calls a week on use of this within a motor control circuit.

I came to the realization, that the cost of these devices ($19.00 - $120.00) makes them such a commodity...that I will be seeing more and more of them in place of NEMA devices.

It's not a bad thing, if used correctly.

Carl Lee Tolbert
Technical Support
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#80185 - 03/14/02 04:39 PM Re: Overcurrent Protection
Webmaster Offline


Registered: 10/07/00
Posts: 3142
Loc: NY, USA
(Posted for ctolbert)

This shows what the MSP looks like. I also wrote a paper on this, that you may be interested in.

- Carl

[This message has been edited by Webmaster (edited 03-14-2002).]


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