44 Program features
A deceleration ramp can be defined for emergency stop (“Off3” mode).
Settings
• Menu
Motor control .
• Speed reference ramping: Parameters 23.11…23.15 and 46.01
(pages 226 and 319).
• Torque reference ramping: Parameters01.30, 26.18 and 26.19
(pages 166 and 238).
• Frequency reference ramping: Parameters 28.71…28.75 and 46.02
(pages 248 and 320).
• Jogging: Parameters 23.20 and 23.21 (page 227).
• Motor potentiometer: Parameter 22.78/22.79 (page 225).
• Emergency stop (“Off3” mode): Parameter 23.23 Emergency stop time
(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 22 Speed reference selection (page 217) and 28 Frequency
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 (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.
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.
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