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Guru

Join Date: Sep 2016
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Magnetic Solenoid

08/10/2017 11:55 PM

Hi, guys.

I came along with a sort of an issue about solenoids and core. One of our service provider says, the magnetic core broke instead of the coil(see pic above).

As far as your experience is this possible? The core is just a metal/stainless made may be, how come it can loss its magnetic property so easily instead of a burnt solenoid coil.

Your insights are much appreciated.

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Pathfinder Tags: Magnetic Brake Solenoid
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Guru

Join Date: Mar 2007
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#1

Re: Magnetic Solenoid

08/11/2017 12:30 AM

Well if the valve gets stuck it can overheat and lose it's magnetic properties....but you just need to let it cool down and unstick the valve...eventually the coil will fail....

http://www.rossdecco.com/solenoid-troubleshooting.html

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Power-User

Join Date: Sep 2016
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#2

Re: Magnetic Solenoid

08/11/2017 2:20 AM

The magnetic flux is much higher inside the solenoid than inside it. That is why the steel melts first. After all, that is how induction heaters work.

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Guru

Join Date: Apr 2010
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#3

Re: Magnetic Solenoid

08/11/2017 9:08 AM

What does "broke" mean? Someone needs to look at it to see what happened. Ask them to send it back to you, if possible.

You can spend a lot of time trying to understand an event based on a description that may or may not be accurate.

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Engineering Fields - Electrical Engineering - Been there, done that, still doing it. Engineering Fields - Control Engineering - New Member

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#4

Re: Magnetic Solenoid

08/11/2017 9:19 AM

Certainly this is possible. It all depends on what they mean by a "broke" core.

If the core is actually the moving part to move something then easily the mechanical linkage can get lost. If this core is actually a magnet then it is possible to lose the magnetic field by exceeding the Curie temperature but damn that's hot. The core might have been mechanically broken in such a fashion that the field strength was too low at a critical location. That's just a few of the possibilities I can think of.

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#5

Re: Magnetic Solenoid

08/11/2017 10:35 AM

In most cases on solenoid valves, the magnetic "core" is the steel core around which the coil is wound. It is not made from a solid mass, but rather from a stack of thin stamped plates make of grain oriented silicon steel that are stacked on each other to form that shape, then connected together to create that mass. Small coils use rivets or screws to keep them together, larger ones use welds. In your photo, you can see the 4 holes in the core for these screws or rivets. If a screw or rivet breaks, the core partially separates under the magnetic stresses and warps the plates, making it unreasonable to repair (compared to the cost of just replacing it).

Why did that happen? Bad luck mostly, nothing is 100% reliable. But one application issue that can do it is rapid and repeated chattering of the coil circuit, meaning whatever is energizing that coil is not giving it a continuous flow of current to keep it pulled in. That can also happen if the proper voltage is not applied, because the act of pulling in causes a voltage drop, which weakens the magnetic field, which makes it let go, which allows the voltage to increase and the coil to attempt to pull in again, which causes a voltage drop again and this cycle repeats until something breaks or a fuse blows.

So bottom line, after replacing it, thoroughly investigate your coil circuit and control devices for any problems and if there are none, it was just bad luck.

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