Group 3.9.4: Motor Underload
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 P3.9.4.2
(Underload protection: Field weakening area load)
and P3.9.4.3 (Zero frequency load).
The underload curve is a squared curve set between
the zero frequency and the field weakening point. The
protection is not active below 5 Hz (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
IH 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.
If you use long motor cables (max. 100 m)
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 underload protection functions.
Code Parameter Min Max Unit Default ID Description
P3.9.4.1 Underload Flt 0 3 0 713
0 = No action
1 = Alarm
2 = Fault (Stop according to
stop mode)
3 = Fault (Stop by coasting)
See P3.9.4.5 for the underload
mode. When P3.9.4.5 = 0,
Underload is determined by
P3.9.4.2 - P3.9.4.4. When
P3.9.4.5 = 1, the fault is related
to P3.9.4.6.
P3.9.4.2 Fieldweak. Load 10.0 150.0 % 50.0 714
This parameter gives the value
for the minimum torque allowed
when the output frequency is
above the field weakening point.
P3.9.4.3 Zero Freq. Load 5.0 150.0 % 10.0 715
This parameter gives value for
the minimum torque allowed
with zero frequency.
If you change the value of
parameter P3.1.1.4 this
parameter is automatically
restored to the default value.
P3.9.4.4 Time Limit 2.00 600.00 s 20.00 716
This is the maximum time
allowed for an underload state
to exist.
P3.9.4.5 UnderloadDetectMode
Motor
Torque
Flow Meter
Motor
Torque
1950
0 = Motor Torque
1 = Flowmeter (transducer
defined by P3.23.1)
P3.9.4.6 Minimum Flow 1 214748 l/min 300 1951
Value to determine underload
fault if P3.9.4.5 is 1
99
English (GB)
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