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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).
Calculation of the average and R.M.S. values of primary current.

Identifier  ExFiles\Box 69\1\  scan0007
Date  30th April 1924 guessed
  
-2- Contd.

B. AVERAGE AND R.M.S. VALUES OF PRIMARY CURRENT.

Number of breaks per second = 70
Make ratio r = .500
Then period T' = .0143 secs.
Period of make t' = .500 x .0143 = .00714 second.
Time of break = .00714 second = t"
Time constant ratio = s = t₁/T' = .003795 / .0143 = .2653

x/s = t'/t₁ = 1.882

e ^ (-R/L * t') = e ^ (-t'/t₁) = e ^ -1.882

= 10 ^ -.8182 = 10 ^ (1̄.1818) = .152

whence x = .848.
and current at break C' = x.C₀ = 2.68 amperes

e ^ (-2r/s) = (.152)² = .023

y = 1 - e ^ (-2r/s) = .977.

The average current C = C₀ (r - x s)
= 3.16 (.500 - .225)
= 3.16 x .275 = .870 amperes.

Contd.
  
  


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