Motor Thermal Protection: Motor Ambient Temp. Factor; Motor Thermal Protection: Time Constant; Motor Thermal Protection: Motor Duty Cycle - Vacon NXP Manual

42 • vacon
705

Motor thermal protection: Motor ambient temp. factor

The factor can be set between -100.0%...100.0%.
706 Motor thermal protection: Motor cooling factor at zero speed
The current can be set between 0—150.0% x I
current at zero frequency. See Figure 18.
The default value is set assuming that there is no external fan cooling the motor. If an external
fan is used this parameter can be set to 90% (or even higher).
Note: The value is set as a percentage of the
motor name plate data, par.
current of motor), not the drive's nominal out-
put current. The motor's nominal current is the
current that the motor can withstand in direct
on-line use without being overheated.
If you change the parameter Nominal current of
motor, this parameter is automatically restored
to the default value.
Setting this parameter does not affect the
maximum output current of the drive which is
determined by parameter
707

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 con-
stant. The time constant is the time within which the calculated thermal stage 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 stage the time constant is internally increased to three times the set para-
meter value. The cooling in the stop stage is based on convection and the time constant is
increased. See also Figure 19.
708

Motor thermal protection: Motor duty cycle

Defines how much of the nominal motor load is applied. The value can be set to 0%...100%.
nMotor
ID113 (Nominal
ID107 alone.
Description of parameters
(2.7.8)
(2.7.9)
. This parameter sets the value for thermal
P cooling
Overload area
100%
Par.
ID706=40%
0
Figure 18. Motor thermal current I
(2.7.10)
(2.7.11)
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