Constant Speeds/Frequencies; Critical Speeds/Frequencies - ABB ACS560 Firmware Manual

44 Program features
A deceleration ramp can be defined for emergency stop ("Off3" mode).
Settings
• Menu Motor control

• Speed reference ramping: Parameters
(pages 226 and 319).
• Torque reference ramping: Parameters01.30,
(pages 166 and 238).
• Frequency reference ramping: Parameters
(pages 248 and 320).
• Jogging: Parameters
• Motor potentiometer: Parameter
• Emergency stop ("Off3" mode): Parameter
(page 228).


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 speeds
for speed control and 7 constant frequencies for frequency control.
WARNING: Speeds and frequencies override the normal reference
irrespective of where the reference is coming from.
Settings
Parameter groups
reference chain (page 240).


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
a critical range, the output of the function
reference exits the range. Any instant change in the output is smoothed out by the
ramping function further in the reference chain.
When the drive is limiting the allowed output speeds/frequencies, it limits to the
absolutely lowest critical speed (critical speed low or critical frequency low) when
accelerating from standstill, unless the speed reference is over the upper critical
speed/ frequency limit.
.
23.20 and 23.21
22.78/22.79
22 Speed reference selection
23.11...23.15 and
26.18 and
28.71...28.75
(page 227).
(page 225).
23.23 Emergency stop time
(page 217) and
(22.87 Speed reference act
(22.01 Speed ref unlimited) freezes until the
46.01
26.19
and 46.02
28 Frequency
7) enters