Montana oil and mining journal. [volume] (Great Falls, Mont.) 1931-1953, 1942-07-11
SAYS
The Skin You
Lore to Touch

! The cosmetic and soap manufac-
turers made famous the phrase, 'the
skin you love to touch" and who
doesn't? Why doesn't the electric mo-
tor manufacturers populartze the
phrase "the motor you love to touch?"
Unlike the proverbial redhead, you
want to feel your motors cool Since
hot and cool are relative we must
qualify statements like "too hot to
handle" or "too cool to enjoy" with
our experience. SO it Is with motors.
If YOU depend upon feel alone you
must have experience, otherwise use
a thermometer.
Most open type electric motors are
guaranteed to not exceed a 40 degree
CentiQrade temperature rise, when
carving their rated horsepower load
This rise is above the maximum sur
rounding air temperature of 40 Q. or
a total maximum temperature OF 30 @.
for fun load. A total temperature Of
90 @. is considered a maximum for
open type motors in good condition.
Water boils at 100 @. at sea level
so the maximum operating tempera-
ture of an open type motor is only 10
degrees less than boiling water. Pretty
hot, if you compare it to the sensa-
ton when you stick your finger In
water that is almost boiling. 1t Is too
hot for your motor If you expect it
to last long time.
Good authority says that increasing
the continuous operating temperature
of a motor 8 degrees @. will cut the
life of its insulation in half. That Is,
if a motor operating at 30 @. Is over
loaded so the temperature Is contin-
uously 88 c.. the motor winding viii
last only half as long. Likewise, If
the continuous operating temperature
is reduced from 30 @. to u O., the
motor insulation should last twice as
long.
The temperature of an open motor
NAV be measured with long glass
by placing the bulb in
contact with the hottest part OF the
stator iron or the windings. The iron
temperature may be measured by glu-
ing a one-inch square felt pad 70 the
iron with any good glue. The glue Is
placed around three edges, leaving the
5op edge open for inserting the Their
bulb. The glue generally dries
sufficiently in 80 minutes if the iron
IS warm. In measuring the iron tenn
oerature, do not confuse the IRON
'rane with the laminated stator iron
IS the frame generally operates much
cooler than the stator iron.
The coil temperature can be meas
lred by inserting the bulb between
he coils If they are accessible.
For practical purposes, 1t Is lar
EASIER To measure the load on the
motor with an ammeter and avoid
,verloads of long duration, than to
determine an overloaded condition by
II the motor is apparent-
v not overloaded but is running abb
formally hot, then thermometer test
] worthwhile as a check.
Ry now you should be wondering
yhat you should do. Well. get In the
labit of feeling your motors as often
s practical. You viii soon get an
dea of how hot or cool the various
motors operate. ANY sudden change in
he apparent temperature is a sign to
,ok for trouble. You should feel the
caring housings Of the motor as wen
S the stator iron as bearing failures
ause most motor failures and you can
sually catch a defective bearing II
on get In the habit Of feeling your
lotors as well as your cuties.