DC Starter Coil

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sii

Senior Member
Location
Nebraska
Sorry, I've never seen a contactor coil like this before. Per the diagram on the right, can I just connect the top terminal of A2 to the NC STOP button and the bottom A2 terminal to the NO START button?

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stew

Senior Member
nope. connect one side of the dc to the nc contact of the pushbutton. connect the other side of the dc source to a2. connect the no contact to a1.
 
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BJ Conner

Senior Member
Location
97006
DC Holding

DC Holding

That used to be common in swichgear (ITE Imperial is one ICan remember).
Considerable DC current is required to "pick up" the contactor. Once you have the contactor closed you don't want all that current going through the coil, it will be noisy, get hot and may permanently magnatize the steel in contactor (meaning it may not open when you push the off or stop button). Some contrators use seperate coils some use tapped.
Contactors or starters with a mechanical latching system don't have that problem.:roll:
 
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kwired

Electron manager
Location
NE Nebraska
The NCI contact opens after pickup is accomplished. This places the two coils in series in the left image and completely isolates the pickup coil on the right image. All of this is likely done for you they are just showing you what is there.

Otherwise wire like any other coil, full voltage must be applied to A1 and A2 on the left image and A1 and A2 top on the right image. NO 2 to 3 contact is used for holding coil if a 3 wire start stop control is used, just like other contactors.
 

Besoeker

Senior Member
Location
UK
Sorry, I've never seen a contactor coil like this before. Per the diagram on the right, can I just connect the top terminal of A2 to the NC STOP button and the bottom A2 terminal to the NO START button?

View attachment 5641
Others have pretty much covered it. It takes more current to close the contactor than to hold it in. I've seen this arrangement where the NC contact is sometimes referred to as an economy circuit.

With an AC contactor it happens naturally. There is high current when the pole faces are apart and there is a gap (contactor open) and the current drops when the pole faces close removing the gap in the magnetic circuit.
 
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