Current Limiting For Frequency Control; The Effects Of Current Limiting - Allen-Bradley Kinetix 5700 User Manual

Appendix E Motor Control Feature Support
Current Limiting for
Frequency Control
Aggressive Acceleration, No Current Limiting
16
14
12
10
8
6
4
2
0
0
200 400 600 800
Output Current Operative Current Limit
410
The current limiting module prevents the OutputCurrent value from
exceeding the OperativeCurrentLimit value when the drive is configured in
Frequency Control mode.
Figure 214 - Current Limiting Module
Velocity from Planner
Operative
Current Limit
In Frequency Control mode, OperativeCurrentLimit is the minimum value of
the motor-thermal current limit, inverter-thermal current limit, motor-peak
current limit, drive-peak current limit, and the CurrentVectorLimit value.

The Effects of Current Limiting

Indirect current limiting is available for induction motors configured for
frequency control. You can use this feature to help prevent overcurrent faults
due to aggressive acceleration/deceleration profiles or impact loads. The
Current Limiting attribute uses a PI regulator to control the OutputCurrent
by adjusting the velocity reference.
IMPORTANT When configured for Frequency Control (induction motors only), select the
Figure 215 - Effects of Current Limiting on an Aggressive Acceleration
1600
1000 1200 1400 1800
Time (ms)
Output Frequency
Rockwell Automation Publication 2198-UM002G-EN-P - February 2019
(MAJ)
PI
+
–
Output
Current
Decel and disable stopping action only when the Current Limiting feature is
enabled.
Aggressive Acceleration, Current Limiting Active
70 16
60 14
50 12
40 10
30 8
20 6
10 4
0 2
-10 0
0 200 400
2000
Output Current
Fine
Command
+
–
Velocity
600 800 1000 1200 1400 1600
Time (ms)
Operative Current Limit Output Frequency
Velocity
Reference
70
60
50
40
30
20
10
0
-10
1800 2000