116 ELECTRICAL APPARATUS

circuit, neglecting the primary impedance, 20, to be comparable
with the shaded-coil single-phase motor, it is:

(F + y'>'

n 2 eo^'o0 _ o /
QQ = .~._~- = eoV

T - 4 e°2

n~ A 2

thus :

_ io \/2

v — .
Q

75. As instances are given in the following table the compo-
nent voltages, e'i and e2, the phase angle, 0, between them, the
primary current, io, the torque ratio, t, and the apparent starting-
torque efficiency, v, for the shaded-pole motor with the constants :

Impressed voltage : e0 =100;

Primary exciting admittance : Y = 0.001 — 0.01 j.

6 = 1, that is, uniform air gap.

a = 0.5, that is, half the pole is shaded.

IJ 'j I And for the three motor armatures:

Low resistance: Yi = 0.01 — 0.03 j,
Medium resistance: YI = 0.02 — 0,02 j,
High resistance: YI = 0.03 — 0.01 j;
and for the three kinds of shading coils :
Low resistance: F2.= 0.01 — 0.03 j,
Medium resistance : F2 = 0.02 — 0.02 j,
High resistance: F2 = 0.03 — 0.01 j.
As seen from this table, the phase angle, <£, and thus the start-
ing torque, t, are greatest with the combination of low-resistance
armature and high-resistance shading coil, and of high-resistance
armature with low-resistance shading coil; but in the first case
the torque is in opposite direction — accelerating coil — from what