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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).
Comparative electrical leakage tests on Bakelite material X.616 B.

Identifier  ExFiles\Box 61\1\  scan0085
Date  7th March 1930
  
To Roy.{Sir Henry Royce} from EFC.
X.6011
EFC6/MS17.3.30.

X.6011 Bakelite material X.616 B.

Referring to the letter from Bakelite Ltd. herewith returned, the following are our remarks, which might be communicated to the Bakelite Co:-

The tests carried out on the sample X.616 B. submitted, were comparative tests between two similar articles moulded with this powder and our standard. In regard to the actual nature of the tests, I quote my assistant's remarks as follows:-

"Electrically, and from the point of view of the particular purpose for which this powder would be used, there are two main points. These points are:-

(1) Leakage current at temperatures ranging from atmospheric to 100°C.

(2) The effect on the magnitude of the leakage current of cycles of heating and cooling.

As regards (1) the article to be tested is slowly heated up from atmospheric temperature to 100°C; observations meanwhile being made at temperatures of 20°c, 40°c, 60°c, 80°c, and 100°c. of the leakage conductance at high d.c. pressure (15,000 to 5,000 volts) using electrodes so shaped as to fit closely and cover a fairly large surface area on each side. The ratio, in megohms, of the value of the applied voltage to that of the leakage current in microamperes is then used as a figure of merit, which we say should not be less than 70 at 15°c and 1½ megohms at 80°c. Actually on production parts we get figures of the order of 1,000 at 15°c and 25 megohms at 80°c.
With regard to (2) we have found that, with our standard material, generally there is an improvement as regards leakage with repeated cycles of temperature, and it was in this respect that the sample of Bakelite X.616 B. powder was not in line with that material.
We are, however, repeating these tests, in addition to which we have other tests to make

contd.
  
  


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