SINGLE-PHASE COMMUTATOR MOTORS 395

the speed, So, at which the total torque vanishes, and reduces
the power-factor and efficiency.

218. As an example are shown in Fig. 188 the characteristic
curves of a repulsion motor, with the speed, S, as abscissae, for
the constants:

Impressed voltage: e = 500 volts.
Exciting impedance, main field: Z = 0.25 + 3 j ohms,
cross field: Z' = 0.25 + 2.5 j ohms.

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FIG. 188.

Self-inductive impedance, main field: ZQ = 0.1 + 0.3 j ohms.

cross field: Z2 = 0.025 + 0.075 j ohms,
armature: Zi = 0.025 + 0.075 j ohms,
brush short-circuit: Z4 = 7.5 + 10 j ohms.
Reduction factor, main field: c0 = 0.4.
brush short-circuit: c4 = 0.04.

Hence:

Z3 = 0.08 + 0.60 j ohms.
A = 0.835- 0.014 j.

= a

ja" = 1.20 + 0.02 j.

Xx = 0.031 - 0.007 j.
X4 = 0.1 79 + 0.087 j.
A4 = 4.475 + 2.175 j.
A3 = 0.202- 0.010 j.