Vacon NX Series Applications Manual page 303

PARAMETER DESCRIPTIONS VACON · 303
P cooling
Overload area
100%
I T
ID706=40%
0 Corner freq f n f
Fig. 72: The motor thermal current I curve
T
707 MOTOR THERMAL PROTECTION: TIME CONSTANT 234567 (2.7.11)
Use this parameter to set the motor thermal time constant.
This time can be set between 1 and 200 minutes.
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.
See also Fig. 73 The motor thermal time constant.
708 MOTOR THERMAL PROTECTION: MOTOR DUTY CYCLE 234567 (2.7.12)
Use this parameter to set the factor for the thermal loadability of the motor.
The value can be set to 0%-150%. See Chapter 9.4 Parameters of motor thermal protection
(IDs 704 to 708).
For example, if you set the value to 130%, the motor goes to the nominal temperature with
130% of the motor nominal current.
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