IEC Starters 1

[timm333]

Can someone tell me what the difference is in the selection of NEMA motor starters and IEC motor starters? In NEMA there are sizes like 1, 2, etc. Do IEC starters also have these sizes?

 

[amptramp]

IEC starters also have category ratings similar to NEMA ratings; however, there are many more divisions than the NEMA standards. IEC starters or contactors are sometimes referred to as "application specific", and as such it is important to closely match the load characteristics to the starter rating. For example, a jogging load characteristic may require the selection of a contactor 1 to 2 IEC sizes larger to accommodate the thermal stress created by the repetitive starting currents.

Google NEMA vs IEC for an answer.

 

[Thedroid]

I prefer NEMA in most cases. They seem to last longer, and in most cases are easier to rebuild.

 

[jraef]

My take on the entire issue of contactor sizing is this:

NEMA sizing - designed so that a common electrician can pick out a product based solely on motor size within a group that will work without much thinking about the application specifics. So it is designed around the worst case scenario for any given motor, i.e. inching and plugging duty. Came from the US Automotive industry where production lines changed every year or two, parts and electricians were cheap and plentiful and engineers were rare and expensive.

IEC sizing - designed to be picked out by an electrical engineer from a very specific set of application criteria based on motor size, starting frequency, expected component life, power factor of the load, ambient temperature and the hair color of your firstborn child. Came about in the post war European market in an environment where engineers were plentiful and electricians were not allowed to make such decisions because resources were too scarce to be wasted.

DP (Definite Purpose) = Don't Purchase! Sized to self-destruct at the end-of-equipment-warranty + 1 day.


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[timm333]

Thanks all for the information. Is there some table that I can use to size the IEC starter for particular applications?

 

[jraef]

There are numerous tables and charts, available from each manufacturer.

Here is one from Siemens, the charts start on page 2.

http://cmsapps.sea.siemens.com/controls/icc2010/10IndControl_ pdfs/10IC_02/02_086-117.pdf

The "Sizes" (S00, S0, S2 etc.) shown in this are frame sizes specific to Siemens only.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[rcw retired EE]

jraef- I had to give you a tar for explaining the IEC method of equipment selection so well. I now know why my IEC starters failed - my first born child was bald.

IEC starters work well if we know enough about the application and intended use and do the correct selection. NEMA starters are overkill for most applications which gives them a built in safety factor.

 

[ScottyUK]

Previous discussion... thread238-218718


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

Good to see I am at least consistent...