K.W. Output
a1
178 POWER DISTRIBUTION FOR ELECTRIC RAILROADS.
variation characteristics of a fifteen horse power induction
motor with a rheostat in the armature circuit. Starting at
full output and speed, the speed was gradually lowered
from 1400 r. p. m. to 150 1. p. m. The torque remained
uniform, so that the output was almost exactly proportion-
ate to the speed. 'The relation between them is shown in
curve A. The input meanwhile remained nearly con-
~
1
Speed in 100 p.p.m.
FIG. 97.
stant. B gives the variation of the power factor and C
shows the slight and gradual diminution of the input.
Altogether this motor behaved almost exactly like an
ordinary railway motor with rheostatic control, regulating
quite as well and with closely similar inefficiency.
At full load this motor had about the efficiency of a
fifteen horse power motor of the ordinary kind, but sub-
stantially all the reduction in output by lowering the
speed represented loss of efficiency as is the case with a
series wound, continuous current railway motor with rheo-
e