Generator Field Coils PDF Print E-mail
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Thursday, 31 July 2008

Generator Field Coils

Exploring Electrical Stuff


Archie Dixon writes:

I've been trying to find a good generator stator for my R50s restoration and on everyone that I've found, the insulation on the field windings is coming off or already partially off. There seems to be some kind of varnish that was on them originally.

Has anybody been successful in fixing these with something? I've got one that had one winding wrapped in black electrical tape. Does anybody know anyone that overhauls these? TIA Arch.

Norman Casteneda writes:

The varnish used for insulating magnetic coils in electric motors, transformers and choke coils is specially formulated to withstand heat and hold the windings securely, so as to prevent the coil wires from chafing through and creating electrical shorts or cutting through to the lamination of the iron core plates. Any industrial electrical motor/transformer repair shop can re-dip the coil for you and rebake, for a nominal fee. Of course, this is for a coil that is electrically and mechanically sound. 

Available from Grainger   are two products in aerosol cans, intended for this application. Stock number 1D275 is a green colored epoxy coating; stock number 1D276 is a red colored varnish. I prefer the varnish. 

They may be oven cured or air dried, and may be applied over the existing coatings. DO NOT ATTEMPT TO REMOVE ANY OF THE OLD COATING/VARNISH!!! Follow the directions on the can. Should you opt to do it yourself, careful cleaning (I use brake cleaner/degreaser in a spray can) and handling of the coil is  imperative.Try to saturate the coil with the spray varnish, even if it drips -- the object being to allow the varnish to enter all open gaps and spaces between the coil wires.You may apply several coats, as needed.One can of this varnish will do several coils, several times. Allow the varnish to cure following manufacturer's guidelines. I use a heat lamp for curing when doing this sort of work, as there is a lesser chance of  "overcooking" the winding.

    The coil must be completely dry before returning to service.

     I have no connection with Grainger.I am familiar with their products and have used them successfully in the past.



Last Updated ( Thursday, 31 July 2008 )
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