Rockwell Automation Publication 2198-UM002G-EN-P - February 2019 411
Motor Control Feature Support Appendix E
Figure 216 - 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 186 - Enable Current Limiting via Messaging
Output Current (Arms), Operative Current Limit (rms)
Impact Load, No Current Limiting
Frequency (Hz)
Time (ms)
Output Current
Operative Current Limit
Output Frequency
Output Current (Arms), Operative Current Limit (rms)
Impact Load, Current Limiting Active
Frequency (Hz)
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.
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