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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).
Page of calculations for field winding resistance, cross-sectional area, and equivalent wire gauge.

Identifier  ExFiles\Box 35\4\  scan 148
Date  30th April 1923 guessed
  
-6-

Ampere turns required = 300
Amperes = 108
.. No of turns. - 3
Length of mean turn 9¼" approx.
Therefore total length of field strip

• 4 x 3 x 9¼ + 9 say
• 123"

Estimated resistance for field winding
= .0115 w at 20°C

Whence ohms per 1000' at 20°C
= (12000 / 123) x .0115
= 1.121

C.S. Area = (.00815 / 1.121) = .00673

This is equivalent to round wire of gauge 13 S.W.G.

_______

[Watermark: SNOWDON BOND]
[Watermark: MADE AT CROXLEY]
  
  


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