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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 motor design parameters, including armature dimensions, flux, and conductor numbers.

Identifier  ExFiles\Box 35\4\  scan 035
Date  1st July 1921 guessed
  
-2- Contd.

allow for torque losses, i.e. 72.7 lb-inches.
Suppose we take a useful polar flux density of 6500 lines per cm.2, reckoned on minimum pole face.
This is necessarily low to give a reasonable armature tooth density.

Armature diameter = 2.850"
Armature circumference corresponding to five slot pitches

= 5/29 x π x 2.850". 5/29 = .1725
= 1.54"
= 39 mm.

Length - 2.50" - 63.5 mm.

This gives a useful flux per pole of
6500 x 6.35 x 3.9 = 161,000.

Number of conductors
= (Tb x 10^8) / (1.41 P Ø C)
= (72.7 x 2 x 10^8) / (1.41 x 4 x 161000 x 137)
= 117.

This agrees with 29 slots and coils, with two turns per coil, i.e. 116 conductors.

Motor speed = 810.

Contd.
  
  


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