ACS 300 User’s Manual 63
Chapter 7 - Drive Parameters
Figure 7-6 Motor thermal protection.
When the motor current exceeds the level determined by the
safe operating area, the ACS 300 will begin calculating
excessive temperature rise in the motor. When the ACS 300
has determined that the motor has exceeded its allowable
temperature rise, it will stop the motor and indicate a
“MOTOR TEMP” fault. The fault can be reset, when the
motor has cooled down to a safe temperature. The ACS 300
will continue to calculate the motor temperature even if the
motor is not running. If the ACS 300 is disconnected from
the input power, the overload protection calculation is reset,
and the motor is assumed to be at ambient.
The motor thermal protection function is designed to protect
motors even at low speeds by decreasing the allowable
operation current. This is necessary as the motor´s cooling
fan becomes less efficient at low speeds.
For standard 50 Hz squirrel cage motors typical value for
this parameter is 35 Hz.
MOTOR I
Nominal motor current at full load as indicated on the motor
rating plate. See U/f RATIO, TEMP LIM and Figure 7-6. This
parameter does not need to be set if TEMP LIM is set to
OUTPUT FREQ[Hz]
OUTPUT CURRENT
TEMP LIM
typically 35 Hz
NOM FREQ
I LIMIT
50 Hz
MOTOR I
Continuous safe
operating area
for motor
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