From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The use of synthetic and non-synthetic varnishes for insulating electrical windings.
| Identifier | ExFiles\Box 24\2\ Scan290 | |
| Date | 21th February 1928 | |
| -3- Contd. and the introduction of nitrogen in other cases, but both of these patents were allowed to lapse, as it was found that good results could be found in other ways. Good insulating varnishes of the non-synthetic type dry by absoption of oxygen, and in doing so increase both in bulk and weight, so that the article is usually slightly heavier when dry. It will, therefore, be found advantageous with that class of varnish to expose the articles to heated air. The oven in which the preliminary heating is usually carried out can usually be utilised for this purpose also. This does not apply to the synthetic varnishes, which have to be treated in other ways after impregnation, according to the composition of the material. So far as filling the spaces between the turns in the winding is concerned, this is difficult when using ordinary oil varnishes. It can be done with compound, or with some synthetic varnishes. On the other hand, if the varnish is a good one and impregnation has been carefully carried out according to instructions, a single operation will, in almost all cases, answer every purpose, as in that case no air or moisture will be imprisoned in contact with the wire, and a film of varnish will so thoroughly coat the wire that no action can take place; it is only when this film is not complete, or when it is disturbed afterwards, that a breakdown occurs. That is one of the reasons for impregnating the apparatus after it is all complete, as then no disturbance of the insulation will take place, and no damage will occur. A second reason, very important to the manufacturer, is that it is cheaper to do the work in one or two pieces than in many. Feb. 21st. 1928. (sgd) A.G. Brown. | ||