ABB ACS880-11 - Page 230

230 Parameters
24.41 Speed error window
control enable
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 19.12 and
19.14), or when the drive is a speed-controlled follower (see
page 32).
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 (25.02 Speed proportional gain) which 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 06.19 Speed control status word.
The window boundaries are defined by 24.43 Speed error
window high and 24.44 Speed error window low as follows:
Note that it is parameter 24.44 (rather than 24.43) that defines
the overspeed limit in both directions of rotation. This is
because the function monitors speed error (which is negative
in case of overspeed, positive in case of underspeed).
WARNING! In a speed-controlled follower, the speed
error window must not exceed 21.06 Zero speed limit
for a reliable ramp stop. Make sure both 24.43 and
24.44 are smaller than 21.06 (or speed error window control
disabled) when a ramp stop is required.
0 = Speed error window control disabled
1 = Speed error window control enabled
Disable
Disable 0. 0
No. Name/Value Description Def/FbEq16
Speed (rpm)
0 rpm
Reference + [24.43] rpm
Reference
Reference - [24.44] rpm
Reference + [24.44] rpm
Reference
Reference - [24.43] rpm
Speed error
window
Speed error
window
Forward
Reverse