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#72701 - 12/07/06 02:13 PM Motor Starter?
rad74ss Offline

Registered: 04/19/04
Posts: 154
Loc: Pryor, OK USA
I have been trying to find a definitive definition of a motor starter. The root of the question is whether or not a motor starter is a combined contactor and overload, or if it can be a contactor with a separate overload. On electrical schematics the difference would be between putting a C prefix on the contactor or an S suffix.

I have always used starter to mean a one piece contactor/overload setup. If they are separate I call one piece the contactor and the other the overload so that bill of materials knows that there are supposed to be two items.

Is there an actual definition somewhere? I haven't had luck finding one yet.



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#72702 - 12/07/06 05:08 PM Re: Motor Starter?
HotLine1 Offline


Registered: 04/03/02
Posts: 6791
Loc: Brick, NJ USA
Basically, to the best of my knowledge you described a motor starter above.

As to multiple parts (contactor & sep. OL's) you still have the same thing, you need both.

An "official" decision or definition regarding a 'one piece' or 'two piece' assembly probably does not exist.


#72703 - 12/07/06 05:19 PM Re: Motor Starter?
renosteinke Offline
Cat Servant

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
We've got a bit spoiled...

When I entered the trade, there were plenty on places where the massive old machines had the disconnect, the fuses, the contactor, and the overloads all in separate enclosures!

These days, we get it all combined in nice, neat cabinets.

I don't think calling the separate items a "starter" to be good grammar; I'd expect them to at least be in the same box.

The issue can become even muddier with IEC style gear. With them, the "starter" is but one lump in the control cabinet....

#72704 - 12/07/06 10:57 PM Re: Motor Starter?
jraef Offline

Registered: 07/21/04
Posts: 90
Loc: San francisco, CA, USA
I agree, there is no "official" definition that revolves around the method of connection.

But this might help. There really isn't a "one piece" starter in NEMA designs either; the overload is always a separate device. There are just 2 ways of connecting it to the contactor; close coupled, i.e. with stabs that connect directly to the contactor terminals; or stand alone, where the user must make connections with wire between them. To add to the mix, when you get above NEMA size 4, the overload is completely separate because the power must go through CTs, and only the CT secondaries go through the OLR.

All of these are "starters", because if it is used on a motor circuit, it is a starter. If it is used on something else like a heater element, you don't need the OLR, so it is just a contactor.

#72705 - 12/08/06 01:30 PM Re: Motor Starter?
frank Offline

Registered: 05/29/01
Posts: 361
Loc: windsor ontario canada

#72706 - 12/08/06 07:46 PM Re: Motor Starter?
Rich Thomas Offline

Registered: 03/09/05
Posts: 48
Loc: Seattle, Washington, USA
I've always considered a "starter" had to have the overload relay, whether it was integral to the contactor or separately wired.

Also, a "combination starter" would contain three items, short circuit protection, contactor and overload relay. To be a combination starter, all three components could be separately mounted. However, I also always considered these items needed to be in the same enclosure to be considered a starter.

#72707 - 12/08/06 08:11 PM Re: Motor Starter?
Eddy Current Offline

Registered: 09/26/06
Posts: 112
Loc: Ontario,Canada
Quote from jraef: All of these are "starters", because if it is used on a motor circuit, it is a starter. If it is used on something else like a heater element, you don't need the OLR, so it is just a contactor.

I had a teacher who always said that!


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