INDUCTION MOTOR

67

45. As further instance, consider the conversion into a, syn-
chronous motor of a poor induction motor: a slow-speed motor of
very high exciting current, of the constants:

e0 = 500;
Fo =0.02 - 0.6 j;
ZQ = 0.1 + 0.3 j]
Zi = 0.1 + 0.3 j.

The load curves of this machine as induction motor are given
in Pig. 20.

LOW SPEED INDUCTION MOTOR DIRECT CURRENT EXCITATION FOR UNITY POWER FACTOR BQ Ğ 50O Z0-.1 + .3j V0 - .02 -.6 j 2iğ.1 +• .35 (Z - 1 -f- 2j) SYNCHRONOUS

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FIG. 26.—^Load curves of low-speed high-excitation induction motor con-
verted to synchronous motor, at unity power-factor excitation.
Converted to a synchronous motor, it has the constants:
Synchronous impedance:
Z = 0.1 + 1.97 j.
Calculated in the same manner, the load curves, when vary-
ing the f eld excitation with changes of load so as to maintain
unity power-factor, are given in Fig. 26, and the load curves for
constant field excitation giving a nominal induced voltage:
e = L5 eo
are given in Fig. 27.
As seen, the increase of field excitation required to maintain