Although you change this parameter, it does not have an effect on the maximum output
current of the drive. Only parameter P3.1.3.1 Motor Current Limit can change the maximum
output current.
The corner frequency for the thermal protection is 70% of the value of the parameter
P3.1.1.2 Motor Nominal Frequency.
ff
n
ID706=40%
0
I
T
100%
Overload area
P
cooling
Corner freq
Fig. 55: The motor thermal current I
T
curve
P3.9.2.4 MOTOR THERMAL TIME CONSTANT (ID 707)
The time constant is the time during which the calculated warming curve becomes 63% of its
target value. The length of the time constant is in relation with the dimension of the motor.
The bigger the motor, the longer the time constant.
In different motors, the motor thermal time constant is different. It also changes between
different motor manufacturers. The default value of the parameter changes from dimension
to dimension.
The t6-time is the time in seconds that the motor can safely operate at 6 times the rated
current. It is possible that the motor manufacturer gives the data with the motor. If you know
the t6 of the motor, you can set the time constant parameter with its help. Usually, the motor
thermal time constant in minutes is 2*t6. When the drive is in the STOP state, the time
constant is internally increased to 3 times the set parameter value, because the cooling
operates based on convection.
PARAMETER DESCRIPTIONS VACON · 277
24-HOUR SUPPORT +358 (0)201 212 575 · EMAIL: VACON@VACON.COM
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