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DBR leaking filler material

Teggy1

Aluminum
Joined
Apr 5, 2010
Location
Iowa, USA
The made China made braking resistor showed up today, after 3 weeks in transport from China (Ebay purchase). Unwrapped it, and thought, OH, desicant huh?..... Maybe not. The end cap seems to have been jarred loose sometime in shipping, letting the filler material (very fine sand/silica?) spill out.

So, does anybody know what that filler material is? Is the purpose of that material to be a heat conducting or insulating medium?

If it Ohm's good, should/could I refill it, get it sealed up, and run it?

I would return it but turnaround is ridiculous, and it was relatively inexpensive, $25.00 shipped. I suppose I could mark it up as a learning experience and find another, but if there isn't a problem refurbing it, I'd take that route.

TIA

Teggy1
 
It's just a resistor... if they put something IN it... it would have to be non-combustible. Most of the time, a resistor wouldn't have ANYTHING in it, otherwise it wouldn't cool very well.
 
High power resistors are usually either wire wound or sand filled, sand filled tend to have a lower watts density on the surface, meaning they will not feel as hot if someone were to touch it. The sand is a non-conductive high silica sand, the same stuff that is in fuses, and is used to disspate the heat more uniformly. If the resistor was designed as sand filled and you don't have the sand, it will burn up fairly quickly.

You can put the sand back in, or if you lost it or some of it, you can find a cheap fuse and cut it open to get some more. But the first thing I would be concerned with is why it leaked out. That was supposed to be sealed with a high-temp seal, often ceramic. If that broke, I'm not sure you can easily repair that with anything that's going to last long. Maybe, but I wouldn't know where to start on a recommendation.
 
I'm guessing this is one of the aluminum cased ones that have a diagonal cut on the end........ not too bad, but when damaged like yours, are NDG.... better to get another.

Some of those are not really too great..... I've had them smoke and fail with good cooling and less power than rating.
 
Thanks for the replies guys,

JST, it is one of the diagonal cut end resistors. The end is a thin piece of aluminum pressed in, there was no sealing material.

Anyway, upon further inspection, it looks like it is a semi porous material that was likely poured into the body around the resistor ( ribbon wrapped around a core, ceramic i guess). It was packaged in 1 layer of bubble wrap, and in a plastic bag. Not much protection on the long journey from the communists. It looks like the filler material broke up in transport and deteriorated as it vibrated against itself, letting what appeared to be sand leak out. The end piece opposite the leads, was pushed out of the body, probably from a drop, or mis-handling.

I Ohmed it, and it is right on at 50 Ohms, I might hook it up and run it until it quits, and order something else.

If it fails it should produce an open circuit and just trip the VFD I beleive.

BTW, save your money and buy something already domestic. I am usually a buy once cry once type of person, but I thought I'd give this a shot. How did that work for me?

Thanks again guys.
 








 
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