Vacon 20 CP/X, Applications Manual

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vacon • 29 Description of Groups
3
Parameters of Underload protection (P9.7 to P9.10)
The purpose of the motor underload protection is to ensure that there is load on the motor
when the drive is running. If the motor loses its load there might be a problem in the process,
e.g. a broken belt or a dry pump.
Motor underload protection can be adjusted by setting the underload curve with parameters
P9.8 (Underload protection: Field weakening area load) and P9.9 (
Underload protection: Zero
frequency load
), see below. The underload curve is a squared curve set between the zero fre-
quency and the field weakening point. The protection is not active below 5Hz (the underload
time counter is stopped).
The torque values for setting the underload curve are set in percentage which refers to the
nominal torque of the motor. The motor's name plate data, parameter motor nominal current
and the drive's nominal current I
L
are used to find the scaling ratio for the internal torque val-
ue. If other than nominal motor is used with the drive, the accuracy of the torque calculation
decreases.
If you use long motor cables (max. 100m) together with small drives (
≤
1.5 kW) the
motor current measured by the drive can be much higher than the actual motor
current due to capacitive currents in the motor cable.
Consider this when setting up the motor thermal protection functions.
Code Parameter Min Max Unit Default ID Description
P9.1
Response to 4mA
reference fault
(< 4mA)
0 4 1 700
0 = No action
1 = Warning
2 = Fault
3 = Warning if Start active
4 = Fault if Start active
P9.2
4mA fault detection
time
0.0 10.0 s 0.5 1430 Time limit
P9.3 Earth fault protection 0 2 2 703
0 = No action
1 = Warning
2 = Fault
P9.4 Motor stall protection 0 2 1 709 See P9.3
P9.5 Motor stall delay 0.0 300.0 s 5.0 711
This is the maximum time
allowed for a stall stage.
P9.6 Motor stall min freq. 0.10 320.00 Hz 15.00 712
For a stall state to occur, the
output frequency must have
remained below this limit for
a certain time.
P9.7 Underload protection 0 2 2 713
See P9.3 for the fault
response.
See P9.23 for the underload
mode. When P9.23 = 0,
Underload is determined by
P9.8 - P9.10. When P9.23 =1,
the fault is related to P9.24.
Table 15. Protections group.