Mondo solenoid - up in smoke?.

[itsmoked]

I have an electromagnet that is about 2 feet in diameter.
It has run for years without shutdown.

Recently it had water sprayed on it for several weeks due to a nozzle failure.

The machine was shut down and an overhaul done.

Three weeks later it's turned on and promptly lays waste to the SCR based power supply controlling the magnet.

I fix the controller and suspect the magnet but don't have immediate access to it.

I do the math and come up with an expected resistance for the magnet windings ~ about 2.7 ohms. I ask the user to measure the resistance of the coil. They state it's about 2.5 ohms. (It's fed thru slip rings.)

Being the shewed untrusting field EE that I am, I add a fuse block to the power supply's output circuit supplying the magnet.

The user installs the supply, turns it on, and the output fuse blows simultaneously.

Here's my thinking. Do you agree with me?

I suspect the moisture got to the windings and dropped the resistance.

Measurement with junk meters show that the lead-to-case resistance is about 1Mohm.

Do you think a bake-out would get this thing back on its feet?

Since it runs at about 130VDC is there even voltage room for a bake-out?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Hi Bill, Yeah I've got a minute...

BTW most modern meters are not fooled by a diode so reversing leads will make no difference.

But to humor you I did and there was 'no difference'.



I caught it in full repose as I snuck up on it in the dark and blasted it with my D80 Nikon. You see it here consorting with a Fluke and having a Sharpie.

This is a shot that includes a Megger that was pulled from the hands of Georg Simon Ohm as he laid slumped over it in his lab..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[edison123]

Keith - Will we get the sliced and diced photos of that chuck ?

Muthu

http://www.edison.co.in

 

[Skogsgurra]

No mention of any smoke??? Is it still in there? Or itsmoked?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...