generator bar material between conductor and groundwall
generator bar material between conductor and groundwall
(OP)
Attached is a photo of a stator bar cross section from a 1000+MW 25KV Westinghouse hydrogen/water-cooled generator with Thermalastic insulation system. This is a normal healthy bar cut apart for inspection long ago when machine was wound.
What is the white material between copper and groundwall tape on top and bottom ?
What is the white material between copper and groundwall tape on top and bottom ?
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(2B)+(2B)' ?





RE: generator bar material between conductor and groundwall
Could it be some kind of adhesive or sealant?
desertfox
RE: generator bar material between conductor and groundwall
It would be virtually impossible to get a mica tape to conform tightly to the shape of the composite bar, especially at the bottom where it is concave, so without the resin there would be a significant void which would result in a loss of mechanical strength and perhaps allow movement or vibration of the individual strands within the composite bar.
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If we learn from our mistakes I'm getting a great education!
RE: generator bar material between conductor and groundwall
The Thermalstic insulation system definitely includes epoxy resin and that was my thought also. However, look at the shape of the boundary between the white material and tape at top... it is very straight and regular. I'm trying to imagine a process that would result in resin fill in this very regular shape and I can't.
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(2B)+(2B)' ?
RE: generator bar material between conductor and groundwall
I think edison123 might be well-placed to comment on this as he has a rewind shop: even if he doesn't use the exact process he's a lot more familiar than I am with the materials and how they behave as they are worked.
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If we learn from our mistakes I'm getting a great education!
RE: generator bar material between conductor and groundwall
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(2B)+(2B)' ?
RE: generator bar material between conductor and groundwall
Figure 6:
http://www.vonroll.ch/downloads/CPIRHVM.pdf
Figure 1:
http://www.vonroll.com/downloads/NMTPCRB.pdf
RE: generator bar material between conductor and groundwall
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If we learn from our mistakes I'm getting a great education!
RE: generator bar material between conductor and groundwall
Yes good question. I'm guessing the mastic would be applied and the coil consolidated in a press before taping, which could push the mastic deep inside? I doubt that would be a desired feature since it would seem to inhibit vpi penetration into the inter-strand area which leaves the possibility of undesired voids (although not as undesirable in this interstrand area as in the groundwall)
I do have the coil section available here at my desk. With my fingernail I thought the large white-material area at top/bottom felt softer than the resin-impregnated tape area. However it may have been my imagination: scratching a scissor point accross the coil created a similar scratch in both areas.
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(2B)+(2B)' ?