M-Maxâ„¢ Series Adjustable Frequency Drive - Eaton Corporation

Parameters
Motor Heat Protection (P8.6–P8.9)
The motor temperature protection is based on a calculated
temperature model and uses the motor current set in
parameter P7.1 to determine the motor load. It does not use
a temperature measurement in the motor.
The calculated temperature model cannot protect the motor
if the cooling flow to the motor is influenced, for example, by
a blocked air entry-way.
The temperature model is based on the assumption that the
motor achieves a winding temperature of 284°F (140°C) at
rated speed and an ambient temperature of 104°F (40°C),
with 105% rated load.
The cooling efficiency, without external cooling, is a function
of the speed (corresponding with the output frequency of the
frequency inverter). When the motor is stationary (zero
frequency), heat is also dissipated through the housing surface.
When the motor is under a great load, the current required by
the motor can be higher than the rated operational current.
The current provided by the frequency inverter can be higher
than the rated operational current of the motor. If the load
requires this much current, there is a danger of a thermal
overload. This is especially the case at lower frequencies
(