108

ELECTRICAL APPARATUS

70. Thus, let:
in a low-resistance motor:
Z = r +'jx = 0.1 + 0.3 j,
fc = 0.4, xi = - 0.2,
Z* = - 0.4 j, Zi = - 0.2 j,
that is, both reactances are capacities.
(34): 61 = 62 = 2.23 e0,
* = 5,
that is, the torque is five times as great as on true quarter-phase
supply.
•i = inr-FoTj' •*= oar-iuj'
/ = 10 e0 = i,
that is, non-inductive, or unity power-factor.
#Q
z 0?
g = 1.58,
w = 3.16,
that is, the apparent starting-torque efficiency, or starting torque
per volt-ampere input, of the single-phase induction motor with
starting devices consisting of two capacities giving a true quarter-
phase system, is 3.16 as high as that of the same motor on a
quarter-phase voltage supply, and the circuit is non-inductive
in starting, while on quarter-phase supply, it has the power-
factor 31.6 per cent, in starting.
In a high-resistance motor:
Z = 0.3 +0.1 j,
it is:
fc = 0.4, xi = 0.2,
Z2 = - 0.4 j, Z, = + 0.2 j,
that is, the one reactance is a capacity, the other an inductance.
el = e2 = 0.743 eo,
t = 0.555,
i = 3.33 60,
£o = 3.16 CQ,
q = 0.527,
v = 1.055,