18
Motor Temperature
Many times users are concerned that motors are operating too
hot. It should be understood that a properly-loaded motor will reach
a shell temperature hot enough to cause burns if touched. This is a
normal condition.
The nameplate of the motor may have a specification for RISE.
This is the temperature the shell of
the motor will attain above
ambient (inside the case of the machine, not room ambient). For
example, if the nameplate RISE is 90°C (194°F), and the motor is
operating in a 30°C (86°F) ambient;
the shell of the motor may
attain 120°C (248°F) which is well above the boiling point of
water!
In the absence of a RISE specification, the nameplate will specify
the motor as Class A or B. Class A motors may not exceed 105°C
(221°F). Class B motors may not exceed 130°C (266°F).
Single-phase motors used by NESLAB
are all internally thermally
protected.* The motor nameplate should carry the legend
Ther-
mally protected.
If the motor is still running, it is below the trip
point of the thermal protector; and therefore
is within operating
range. If the motor is indeed too hot, it will cycle on and off on the
thermal protector - and flow will be observed to stop and start.
Internal thermal protectors are all automatic reset. The
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