Rolls-Royce Archives
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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).
Calculations for electrical properties including Back E.M.F., ohmic resistance, and armature values for a motor.

Identifier  ExFiles\Box 35\4\  scan 036
Date  1st July 1921 guessed
  
Contd.
-3-

Back E.M.F. when rolling engine
= Ø Z N P / (60 x 10^8 x b)
= 161,000 x 116 x 810 x 4 / (60 x 10^8 x 2)
= 5.05 volts.

Forward E.M.F. = 9.26 volts.

E.M.F. to overcome ohmic resistance
= 4.21 volts.

Amperes = 137
Total motor ohms = .0307 = R (say)
Let field resistance = R_F
and armature " - R_A
Then R = 6/5 R_A + R_F, say to allow for
brush and com. etc. resistance.
Suppose R_F = .4 R_A

(C.A.V. ZC .45, Lucas A.510, .33,
Bosch S.45 .32).

Then R = (1.20 + .40) R_A
= 1.60 R_A

∴ R_A = .0307 / 1.60 = .0192 w
RF = .0077 w

Contd.
  
  


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