Figure 23 illustrates the relationship between
rated horsepower, speed and normal load WK2
.
We may designate as “inertia factor” the ratio
of actual load WK2 to normal load WK2
. This
varies over a wide range. Typical values are
shown in Figure 24.
NEMA defines pull-in torque as the maximum
constant torque under which the motor will pull
its connected inertia load into synchronism at
rated voltage and frequency, when excitation is
applied. This is sometimes referred to as “load”
pull-in torque.