8 Commissioning/Shutdown
92 of 212
PumpDrive 2
8.8.2.7 Suppressing a frequency range
In the case of critical system conditions, a frequency range can be suppressed to
prevent resonance. An upper and lower speed limit value can be parameterised for
this purpose. If the upper and lower limit speeds have the same rpm setting,
suppression does not occur.
NOTE
Suppressing a frequency range does not take effect in manual mode.
Suppressing a frequency range in closed-loop control mode
If the closed-loop control value exceeds the lower limit speed or undershoots the
upper limit speed, the control system transitions through the resonance range.
Before the resonance range is passed again, the closed-loop control value must have
left it once. In this way, oscillation is reduced when a controller is set to respond
slowly. The effect cannot be avoided altogether, however, if the setpoint is reached
within the confines of the resonance range. In the event that several transitions occur
in closed-loop control mode, a Resonance Range warning is output. This warning is
displayed for 60seconds after the last transition.
Suppressing a frequency range in open-loop control mode
If the open-loop control value is below the mean value between both limit speeds,
the motor remains at the lower limit speed. If the open-loop control value is above
the mean value between both limit speeds, the motor remains at the upper limit
speed. If the mean value is exceeded or undershot, the control system overcomes the
resonance range along the motor protection ramp.
Table65: Upper and lower limit speed
Parameter Description Possible settings Factory setting
3-9-12-1 Lower Limit
Lower speed limit for suppressing the
resonance range in Hz. If the lower and
upper limit frequency are assigned the
same values, there is no suppression. This
function is not supported in manual mode.
Minimum to maximum speed of
motor
0 rpm
3-9-12-2 Upper Limit
Upper speed limit for suppressing the
resonance range in Hz. If the lower and
upper limit frequency are assigned the
same values, there is no suppression. This
function is not supported in manual mode.
Minimum to maximum speed of
motor
0 rpm
8.8.2.8 Dry running protection and protection against hydraulic blockage
If the function is active, dry running of the pump triggers an alert followed by
tripping. Hydraulic blockage, or pumping against a closed pipeline, initially leads to a
warning and ultimately to an alert followed by tripping.
NOTE
If dry running protection was activated via an external sensor, sensorless dry
running detection is inactive.
Protection against dry running and hydraulic blockage is based on a learning
function that is run through once.
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