Sections: Pole | Yoke & Ring | Field Magnet Coil

Yoke Design

<-- Back Items 07 - 10

Item 50.11. Flux Density in Frame, B"y
Approximately equal to, or somewhat less than, the maximum density of the core, B"g_c. Trial value: 90,000 lines per sq. in.

Item 50.12. Cross Section of Yoke Ring, A_y
Use: A_y = F_FL x l_f / 2 x B"y

Axial Width Yoke Ring, l_yoke
Assumed to be about the same length as the armature length, l_a.

Thickness of Yoke Ring, w_yoke
Use: w_yoke = A_y / l_yoke.

Item 50.13. Outside Diameter of Frame, D_frame
Use: D + 2( x + w_core + w_yoke) + overhang
The yoke overhang, usually measured parallel to shaft is about 2 inches.

Item 50.14. Ampere-turn per pole

Flux entering armature per pole, F
Use: E x hz x 6 x 10⁸ / ( p x N x Z).

Flux Density @ Armature Core Below the Teeth, B"g
Use: B"g = (F/2) x CS_t .

Flux Density @ Pole Core, B"g_c
Use: B"g_c = 1.125 F / A_c .

Flux Density @ Yoke Ring, B"y
Use: B"y = 1.15F/2 x (w_yoke x l_yoke).

Flux Density @ Air Gap, B"a
Use: B"a = F / (0.85r + 0.15)tl_a.

Ampere turns per inch
Refer to Fig.61. for the value of magnetization for Armature, (TI)/in._a, Pole Core, (TI)/in._c, and Yoke Ring, (TI)/in._y.

Ampere-turns @ Armature Core Below the Teeth, (TI)_a
Use: (TI)_a = (TI)/in._a x t/3.

Ampere-turns @ Pole Core, (TI)_c
Use: (TI)_c = (TI)/in._c x c
Where: c is the length of the pole core.

Ampere-turns @ Yoke Ring, (TI)_y
Use: (TI)_c = (TI)/in._y x b
Where: b is the length of the yoke ring.

Ampere-turns @ Yoke Ring, (TI)_t
Refer to Fig. 50: Ampere-turn required for air-gap and teeth given, the air gap density.

Ampere-turns for Total Magnetic Circuit, (TI)
use: (TI)_a + (TI)_c + (TI)_y + (TI)_t.

Items 47.1 - 47.3

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