ABB ACS880-x04, Firmware Manual

Page: 43 / 604

Program features 43
The change rate of the motor potentiometer function (page 69 ) is adjustable. The
same rate applies in both directions.
A deceleration ramp can be defined for emergency stop (“Off3” mode).
Settings
• Speed reference ramping: Parameters 23.11 … 23.19 and 46.01
(pages 220 and 335 ).
• Torque reference ramping: Parameters 01.30 , 26.18 and 26.19
(pages 119 and 245 ).
• Frequency reference ramping: Parameters 28.71 … 28.75 and 46.02
(pages 255 and 336 ).
• Jogging: Parameters 23.20 and 23.21 (page 223 ).
• Motor potentiometer: Parameter 22.75 (page 218 ).
• Emergency stop (“Off3” mode): Parameter 23.23 Emergency stop time
(page 223 ).
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Constant speeds/frequencies
Constant speeds and frequencies are predefined references that can be quickly
activated, for example, through digital inputs. It is possible to define up to 7 constant
speeds for speed control and 7 constant frequencies for frequency control.
WARNING: Constant speeds and frequencies override the normal reference
irrespective of where the reference is coming from.
The constant speeds/frequencies function operates on a 2 ms time level.
Settings
Parameter groups 22 Speed reference selection (page 212 ) and 28 Frequency
reference chain (page 250 ).

Critical speeds/frequencies
Critical speeds (sometimes called “skip speeds”) can be predefined for applications
where it is necessary to avoid certain motor speeds or speed ranges because of, for
example, mechanical resonance problems.
The critical speeds function prevents the reference from dwelling within a critical band
for extended times. When a changing reference (
22.87 Speed reference act 7 ) enters
a critical range, the output of the function ( 22.01 Speed ref unlimited ) freezes until the
reference exits the range. Any instant change in the output is smoothed out by the
ramping function further in the reference chain.