description of parameters
vacon
•
35
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f
f
n
par.
2.8.7=40%
100%
0
N
X
1
2
k
6
2
2.8.7
Motor thermal protection: Cooling factor at zero speed
The cooling power can be set between
0—150.0% x cooling power at nominal
frequency. See Figure 14.
Figure 14. Motor cooling power
2.8.8
Motor thermal protection: 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 bigger the
time constant. The time constant is the time within which the calculated 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 2xt6. If the drive is in stop state the time constant is internally
increased to three times the set parameter value. The cooling in the stop state is based
on convection and the time constant is increased. See also Figure 10.
Note: If the nominal speed (
are changed this parameter is automatically set to the default value (45).
