User manual

f
f
n
P13.9=40%
0
I
T
100%
Overload area
P
cooling
Corner freq
parameter descriptions vacon • 131
24-hour support [phone] • Email: [e-mail]
9
Figure 9.18: Motor thermal current IT curve
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 frame and/or
slower the speed of the motor, the longer the time constants. The time con-
stant 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 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 9.19.
The cooling in stop stage is based on convection and the time constant is in-
creased.