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Operation
8.3 Setpoint channel and closed-loop control
Direction of rotation changeover is initiated as follows:
• For control via PROFIBUS using control word 1, bit 11
• For control via the cabinet operator panel (LOCAL mode) using the "Reverse direction of
rotation" button
Note
Only one direction of rotation is enabled in the factory setting.
8.3.3
Suppression bandwidths
Variable-speed drives can generate critical whirling speeds within the control range of the entire
drive train. This prevents steady-state operation in their proximity, that is, although the drive can
pass through this range, it must not remain within it because resonant oscillations may be
excited.
The suppression bandwidths allow this range to be blocked for steady-state operation. Because
the points at which critical whirling speeds occur in a drive train can vary depending on age or
thermal factors, a broader control range should be blocked.
To ensure that the speed does not constantly increase and decrease in the suppression
bandwidth (speeds), the bands are assigned a hysteresis.
Specify a minimum speed in order to block a specific range around the stopped state for
stationary operation.
8.3.4
Speed limitation
Speed limitation can limit the maximum permissible speed of the entire drive train to protect the
drive and load machine/process against damage caused by excessive speeds.
8.3.5
Ramp-function generator
The ramp-function generator limits the rate at which the setpoint changes when the drive is
accelerating or decelerating. This prevents excessive setpoint step changes from damaging the
drive train. Two ramp function generators are available; these can be selected using parameters.
To improve the control properties with regard to load surges, set additional rounding times in the
lower and upper speed range.
Setting rounding times has the following advantages:
• It protects mechanical components, such as shafts and couplings.
• It prevents the actual speed value from being overshot when the setpoint is approached,
thereby improving control quality.
102
3rd Party LCI Control Upgrade
Operating Instructions, 02/2022, A5E31872818
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