ABB ACS880 Firmware Manual page 323

No. Name / Range /
Selection
Description
Enables/disables (or selects a source that
enables/disables) speed error window control,
sometimes also referred to as deadband control or
strip break protection. It forms a speed supervision
function for a torque-controlled drive, preventing the
motor from running away if the material that is being
held under tension breaks.
Note: Speed error window control is only effective when
the Add operating mode is active (see parameters
and 19.14), or when the drive is a speed-controlled
follower (see page 74).
In normal operation, window control keeps the speed
controller input at zero so the drive stays in torque
control.
If the motor load is lost, then the motor speed will rise
as the torque controller tries to maintain torque. The
speed error (speed reference - actual speed) will
increase until it exits the speed error window. When
this is detected, the exceeding part of the error value
is connected to the speed controller. The speed
controller produces a reference term relative to the
input and gain (25.2 Speed proportional
the torque selector adds to the torque reference. The
result is used as the internal torque reference for the
drive.
The activation of speed error window control is
indicated by bit 3 of 6.19 Speed control status
The window boundaries are defined by
error window high and
as follows:
gain) which
24.43 Speed
24.44 Speed error window low
Parameters 323
Def / Type
FbEq 16b / 32b
19.12
word.