User manual

128 • vacon parameter descriptions
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9
9.12 Protections (Control panel:Menu Par->P13)
13.5 STALL PROTECTION
0 = No action
1 = Alarm
2 = Fault, stop function
3 = Fault, coast
The motor stall protection protects the motor from short time overload situa-
tions such as one caused by a stalled shaft. The reaction time of the stall pro-
tection can be set shorter than that of motor thermal protection. The stall
state is defined with two parameters, P13.11 (Stall current) and P13.13 (Stall
frequency limit). If the current is higher than the set limit and the output fre-
quency is lower than the set limit the stall state is true. There is actually no
real indication of the shaft rotation. Stall protection is a type of over current
protection.
13.6 UNDER LOAD PROTECTION
0 = No action
1 = Alarm
2 = Fault, stop function
3 = Fault, coast
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 P13.14 (Underload protection: Field weakening area load)
and P13.15 (Underload protection: Zero frequency load), see the figure below.
The underload curve is a squared curve set between the zero frequency and
the field weakening point. The protection is not active below 5Hz (the under-
load 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, pa-
rameter motor nominal current and the drive's nominal current IL are used to
find the scaling ratio for the internal torque value. If other than nominal motor
is used with the drive, the accuracy of the torque calculation decreases.
The default parameter value of the underload protection time limit is 20 sec-
onds, which is the maximum time allowed for an underload state to exist be-
fore causing a trip according to this parameter.