Resistor brazing

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Abhi

Abhi

I m an Engineer
Location
Jharkhand, India
Occupation
Electrical & Instrumentation Engineer
I think resistor material is made up of tungsten used in vfds, may be I am be wrong.
so how to weld or braze if it is broken somewhere in the middle part.
I mean what welding rod, gas for heating, etc for a proper joint bcoz it is mounted on a shaky platform or if i say on a crane itself.
 
Abhi said:
I think resistor material is made up of tungsten used in vfds, may be I am be wrong.
so how to weld or braze if it is broken somewhere in the middle part.
I mean what welding rod, gas for heating, etc for a proper joint bcoz it is mounted on a shaky platform or if i say on a crane itself.
Click to expand...

I'm not sure that "repairing" a resistor is the sort of thing that should be attempted in the field. How big is this resistor, what is it for, and why not just replace it?
 
gadfly56 said:
I'm not sure that "repairing" a resistor is the sort of thing that should be attempted in the field. How big is this resistor, what is it for, and why not just replace it?
Click to expand...

its 8 ohms, 5 KW rating resistor
20 strips of resistor is combined in series to form 8 ohms
 
180614-1024 EDT

Tungsten would not normally be used as a resistor resistance material.

See http://www.resistorguide.com/materials/ nichrome.

Power resistors do not run red hot like cooking elements, but the wire does get quite hot.

https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

I could not find one table with nichrome, brass, steel, and copper with their thermal conductivities. You have to go to different tables and different units. But brass is a better conductor of both heat and electric current than nichrome. I don't think brass used to solder nichrome wou;d be at too high a temperature when the nichrome is used as resistor material.

The following two links do not work from this post.

https://en.wikipedia.org/wiki/Nichrome
https://en.wikipedia.org/wiki/List_of_thermal_conductivities

.
 
gar said:
180614-1024 EDT

Tungsten would not normally be used as a resistor resistance material.

See http://www.resistorguide.com/materials/ nichrome.

Power resistors do not run red hot like cooking elements, but the wire does get quite hot.

https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

I could not find one table with nichrome, brass, steel, and copper with their thermal conductivities. You have to go to different tables and different units. But brass is a better conductor of both heat and electric current than nichrome. I don't think brass used to solder nichrome wou;d be at too high a temperature when the nichrome is used as resistor material.

The following two links do not work from this post.

https://en.wikipedia.org/wiki/Nichrome
https://en.wikipedia.org/wiki/List_of_thermal_conductivities

.
Click to expand...

The links worked perfectly fine for me from inside your post.
 
Abhi said:
I think resistor material is made up of tungsten used in vfds, may be I am be wrong.
so how to weld or braze if it is broken somewhere in the middle part.
I mean what welding rod, gas for heating, etc for a proper joint bcoz it is mounted on a shaky platform or if i say on a crane itself.
Click to expand...

I am not sure you can weld it back together. Might be easier to just splice it.
 
It will be NiCh (Nickel - Chromium alloy) resistance wire, and it is not repairable. If you try to repair it, you add resistance to that element and when used in a grid like that, that element in the gris simply conducts less, so the other elements carry more of the workload and fail sooner. Just replace that element.
 
Jraef said:
It will be NiCh (Nickel - Chromium alloy) resistance wire, and it is not repairable. If you try to repair it, you add resistance to that element and when used in a grid like that, that element in the gris simply conducts less, so the other elements carry more of the workload and fail sooner. Just replace that element.
Click to expand...

he said they were in series so if he spliced it back together the whole resistor might have a slightly higher resistance. probably not enough to make any real difference.

the ends of the resistors made this way just have terminals that are clamped on to the wire. They work fine. No reason a proper splice would not work.
 
Andy Delle said:
This is not something you want to kludge in a high power VFD.
Click to expand...

Agreed. Or have the manufacturer field repair it, if it can be done. I'm guessing you can have a really spectacular failure in a device moving 5 kW through it if it doesn't go back together right.
 
petersonra said:
he said they were in series so if he spliced it back together the whole resistor might have a slightly higher resistance. probably not enough to make any real difference.

the ends of the resistors made this way just have terminals that are clamped on to the wire. They work fine. No reason a proper splice would not work.
Click to expand...

Does anyone have a schematic or picture of this thing?
 
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