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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).
Laboratory tests for a new type of circular condenser for a battery ignition system.

Identifier  ExFiles\Box 165\5\  img055
Date  23th August 1932
  
X6052

To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Wst.
c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager}
c. to Hy.{Tom Haldenby - Plant Engineer} Hdy.{William Hardy}
c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer}

Hs{Lord Ernest Hives - Chair}/Wst.3/KT. 23.8.32.

NEW TYPE OF CIRCULAR CONDENSER
FOR R.R. BATTERY IGNITION.

We have now completed laboratory tests on this condenser which has been primarily designed for the new double breaker Peregrine battery ignition distributor.

Our tests consisted of ascertaining the variation of capacity and the insulation resistance with rise of temperature. These factors are important owing to the fact that the temperature of the condenser when in use on the car can easily reach 150C. It is important with coil ignition that the capacity and leakage through the condenser should be kept as low as possible, and particularly must there be no appreciable rise of capacity and leakage through the condenser with temperature.

We attach herewith curves illustrating the tests we have carried out on these condensers. It will be seen that the new type circular condenser wound with paraffin wax impregnated paper instead of varnish paper, gives a much better performance, the capacity remaining almost constant from ambient temperature to 100°C, whereas the capacity of the standard condenser rises almost 100%. It will also be seen that the insulation resistance of the present standard condenser remains fairly constant with temperature, and although the paraffin wax paper condenser insulation resistance drops considerably with temperature, the minimum resistance of this condenser, even at 100°C, is considerably higher than the present standard.

This rapid drop of insulation resistance with temperature is a well known characteristic of paraffin wax paper. The fact that the new condenser's capacity remains constant with temperature and that the insulation resistance is also greater than standard will mean that when the coil and ignition distributor is hot, we shall be getting a much better efficiency from the battery ignition, as the energy in the primary winding of the ignition coil at break, will be greater.

Although the damping effect, due to the reduction of insulation resistance, with temperature is proportionately greater than the standard condenser.
  
  


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