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Details on reterminating generator windings

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JohnMcNutt

Industrial
Mar 3, 2013
111
I have a possible project to convert a 3 phase Y connected 4 wire generator head to single phase.

I am comfortable with the theory of how everything will work. I plan to break one wire out of the Y-point and bring it up to the connection box so it can be joined to the end of one of the existing hot leads.

However, I would like some info on how to terminate the magnet wire into motor lead wire. Having no dead units to sacrifice.

I am imagining since this will be a once in a while type of occurrence to avoid special tooling, to crimp the (stripped/sanded) magnet wires into a bare butt splice, and then solder or braze. But what filler material or process to use has me wondering to avoid damage. Then cover with a fiberglass sleeve which is what it looks like the OEM does. And then zip tie and coat with Glyptal.

Ideas?
 
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What size is this generator? Have you inspected the set yet? Generally the wye point is brought out to terminals in a gen-set.
If this is an old ten lead Delco set, you may use the Collins or Bar-Diamond connection to avoid breaking the internal wye point.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
15 kw, 4 pole. I have used your Collins connection to good effect on 10 lead machines. However I think this is going to be a 4 lead so my plan is to make it 5 leads. Have not dug into it yet.
 
Silver solder as used by model boilermakers would be a good choice: much higher melting point than soft solder but not as high as brazing. Ideal heat source would be a small oxy-propane torch because it is both hot and controllable, but a plain propane torch would do at a push.
 
I agree with crimping before soldering. Back in the day when soldered connections were common, our code required connections to electrically and mechanically secure before soldering.
I sometimes use heat-shrink tubing over RTV silicon over critical butt splices. Then the fibre-glass sleeve overall.
If you are familiar with the Collins connection, you have probably also encountered instances in the field where someone has just abandoned one phase and used two phases at 120:208 Volts.
For anyone wondering why you don't use this solution;
All of the accepted reconnection schemes to convert three phase to single phase result in a 1/3 loss of rated KVA, or 66.7% of the original KVA rating..
Using two phases instead of reconnecting for single phase results in the available KVA for 208 Volt loads dropping to 58% of the original rating.


Bill
--------------------
"Why not the best?"
Jimmy Carter
 
What kind of silver solder composition are we talking about?

Otherwise I am thinking I can just use standard lead-free solder because the melt point is at least 220C. That gives a working temperature of 171C which is greater than the class F insulation of 155C.

 
I would go with the lowest possible temperature. You may also be able to clamp a set of vice-grips to the winding conductor near the butt splice as a heat sink. I would be concerned with heat conduction down the conductor into the winding and possible insulation damage.
I don't often disagree with Scotty but in this instance I would choose a different compromise and accept lower strength to gain lower soldering temperatures. I may be in error.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
I'm probably looking at this from a 'big machine' perspective. It's not often I disagree with Bill... ;-)

My logic is that you don't want the joint liquifying under fault conditions. A standard lead-free solder will probably be fine, and if you don't have the gear to go work with the silver solders then it doesn't make sense to try to use them. They are really closer to brazing alloys than solders in terms of working temperature. The easiest ones to work with were cadmium-bearing until a few years ago, and the new ones don't flow as nicely. This sort of thing: Johnson-Matthey Silver-Flo
 
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