parameter descriptions vacon • 85
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13.8 MTP:AMBIENT TEMPERATURE
When the motor ambient temperature must be taken into consideration, it is
recommended to set a value for this parameter. The value can be set between
-20 and 100 degrees Celsius.
13.9 MTP:ZERO SPEED COOLING
The cooling power can be set between 0 - 150.0% x cooling power at nominal
frequency. See Figure 9.14.
T
P
Figure 9.14: Motor cooling power
13.10 MTP:THERMAL TIME CONSTANT
This time can be set between 1 and 200 minutes.
This is the thermal time constant of the motor. The bigger the motor, the long-
er the time constants. The time constant is the time within which the calculat-
ed thermal model has reached 63% of its final value.
The motor thermal time is specific to the motor design and it varies between
different motor manufacturers.
If the motor's t6-time (t6 is the time in seconds the motor can safely operate
at six times the rated current) is known (given by the motor manufacturer) the
time constant parameter can be set basing on it. As a rule of thumb, the motor
thermal time constant in minutes equals to 2 x t6. If the drive is in stop state
the time constant is internally increased to three times the set parameter val-
ue. See also Figure 9.15.
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