
Rockwell Automation Publication 2198-UM002E-EN-P - February 2018
331
Motor Control Feature Support
Appendix D
Figure 163 - Effects of Current Limiting on an Impact Load
Current limiting for frequency control is not enabled by default. You can
enable via messaging by using the following device-specific attributes.
Table 155 - Enable Current Limiting via Messaging
O
utp
ut C
urr
ent
(A
rm
s)
, Op
er
at
iv
e C
urr
ent Lim
it (rm
s)
Impact Load, No Current Limiting
Fr
eq
ue
nc
y (
H
z)
Time (ms)
Output Current
Operative Current Limit
Output Frequency
O
utp
ut C
urr
ent
(A
rm
s)
, Op
er
at
iv
e C
urr
ent Lim
it (rm
s)
Impact Load, Current Limiting Active
Fr
eq
ue
nc
y (
H
z)
Time (ms)
Output Current
Operative Current Limit
Output Frequency
4000
4200
4400
4600
4800
5000
5200
5400
5600
5800
12
10
8
6
4
2
0
70
60
50
40
30
20
10
0
-10
12
10
8
6
4
2
0
70
60
50
40
30
20
10
0
-10
4000
4200
4400
4600
4800
5000
5200
5400
5600
5800
TIP
We recommend you leave the Kp, Ki, Kd gains at the default values.
Attribute
Offset
Type
Attribute Name
Conditional
Implementation
Description
3022
SINT
Current Limiting
Enable
Frequency Control
Induction Motor only
When enabled, limits the rate of change to the velocity reference during high-current situations for
improved current limiting. This feature is only active when executing an MDS command and when
configured for Frequency Control.
0 = Current Limiting is disabled
1 = Current Limiting is enabled
3023
REAL
Current Limiting Kd
Derivative gain for the current limiting function. Only functional when configured for Frequency
Control and when executing an MDS command. Units of seconds.
3024
REAL
Current Limiting Ki
Integral gain for the current limiting function. Only functional when configured for Frequency Control
and when executing an MDS command. Units of feedback counts / (Amp, inst* Seconds).
3025
REAL
Current Limiting Kp
Proportional gain for the current limiting function. Only functional when configured for Frequency
Control and when executing an MDS command. Units of feedback counts / Amp, inst.
IMPORTANT
For induction motors greater than 5 Hp, it is recommended that the Stability
Control feature also be enabled when Current Limiting is enabled.