Vacon 10 Complete User's Manual page 87

•
84 vacon
13.7 M
OTOR THERMAL PROTECTION
If tripping is selected the drive will stop and activate the fault stage, if the tem-
perature of the motor becomes too high. Deactivating the protection, i.e. set-
ting parameter to 0, will reset the thermal model of the motor to 0%.
The motor thermal protection is to protect the motor from overheating. The drive is
capable of supplying higher than nominal current to the motor. If the load requires
this high current there is a risk that the motor will be thermally overloaded. This is
the case especially at low frequencies. At low frequencies the cooling effect of the
motor is reduced as well as its capacity. If the motor is equipped with an external fan
the load reduction at low speeds is small.
The motor thermal protection is based on a calculated model and it uses the output
current of the drive to determine the load on the motor.
The motor thermal protection can be adjusted with parameters. The thermal current
I specifies the load current above which the motor is overloaded. This current limit
T
is a function of the output frequency.
CAUTION! The calculated model does not protect the motor if
the airflow to the motor is reduced by blocked air intake grill.
9
Underload curve at
nominal freq. = 50%
Underload curve at
zero freq. = 10%
5 Hz
Figure 9.13: Underload protection
0 = No action
1 = Alarm
2 = Fault, coast
parameter descriptions
Torque
Underload area
Field weakening
point, P1.11
Tel. +358 (0)201 2121 • Fax +358 (0)201 212205
f