<-- Back Items 125 - 139

Item 140. Dimension of Motor Casing, D_c × L_c
Item 140a. Outside Dimater of Motor Casing, D_c
Use: D_c = [ 1.1 + (HP / 100 ] × D_O
Where: D_O, Outside Diameter of Stator, see item 34b and.
Item 140a. Length of Motor Casing, excluding Bearing Spaces, L_c
Use: L_c = 2.35 la
Where: la, Gross length of Armature, see item 13
This dimension excludes the additional lengths for bearing spaces at both ends.

Item 141. Copper Loss for the Embedded Copper in the Armature Slots, W_{cu e}
Use: W_{cu e} = W_{A cu} [ 2 la /mlt ]
Where: mlt, Mean Length per Turn, see item 29 and.
W_{A cu}, Stator Copper Loss, see item 32.

Item 141. Amount of Radiated Losses from Core, W_RL
Use: W_RL = W_{A fe} + W_{cu e}
Where: W_{A fe}, Stator Iron Loss, see item 39.

Item 142. Total Cooling Surface, S
Use: S_C = S_O + S_I + S_D
Item 140a. Outside Cooling Surface, S_O
Use: S_O = p × Do × la
Item 140b. Inside Cooling Surface, S_I
Use: S_I = p × D × l_a
Item 140c. Ducts and Ends Cooling Surface, S_D
Use: S_D =p/4 [ (Do)² - (D)² ] × (2 #v + 2 )
Where: #_v is the number of vent ducts, item 14. Increase this number, #_v when Temperature Rise is found to exceed the limit.

Item 144. Watts Dissipated for Self-Cooling Ventilation, W_SC
Item 144a. Watts Dissipated for Outside Cooling Area, w_O
Use: w =w_O +w_I +w_D
Use: w_O = S_O × c_O
Where: Cooling Coefficient for Outside Surface, c_O
c_o = (1500 + v) / 100,000. The peripheral velocity, v is zero since no air is thrown against the outside surface.
Item 144b. Watts Dissipated for Inside Cooling Area, w_I
Use: w_I = S_I × c_I
Where: Cooling Coefficient for Inside Surface, c_I
c_I = (1500 + v) / 100,000. The peripheral velocity, v is that of the surface of the stator equal to the rotor peripheral velocity, v.
Item 144c. Watts Dissipated for Ducts and Ends Cooling Area, w_D
Use: W_D = S_D × c_D
Where: Cooling Coefficient for Ducts and Ends Surface, c_D
c_D = (v / 3) / 100,000.

Item 145. Approx. Temp. Rise of Armature, TR
Use: TR = W_RL / w
By Formula: TR = 0.9 × (40,000) × W_FL / (30,000 × v ) × D_c × L_c
Should not exceed, 45°C - 50°C. Should NOT BE LESS THAN 20°C. For motors 75HP or more at 3,600 rpm and 200HP or more below 3,600 rpm, TR should NOT EXCEED 60°C.
Where: W_FL = SL_total, Total Losses, Item 56.

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