Rockwell Automation WebPak 3000 DC Drive Application Workbook Version 1.1 - Manual (Page 46)

7-2 WebPak 3000 DC Drive Application Workbook, Version 1.1
•
JBAR = time to accelerate an empty core to base speed with full shunt field
excitation. The results of speed loop self tuning should yield a value for JBAR
in SYSTEM INERTIA (P.222) or it can be calculated as:
JBAR (seconds) = Total Inertia (lb-ft 2 ) X Motor Base Speed (RPM)
308 X Motor Full Load Torque (lb-ft)
•
DI = the diameter of the roll used to calculate JBARI
•
D
EC
= empty core diameter
•
DBARI = normalized instantaneous diameter = D
I
/
Dec
•
W
I
= width of product on roll when JBARI is measured
•
W
MAX
= maximum product width
•
WDBARI = normalized product width = W
I
/ W
MAX
▲
Set WIDTH / BUILDUP FACTOR (P.872), which is configured as a ratio of maximum
material width. The parameter is normalized so that maximum width = 1.000.
P.872 can be arbitrarily set to provide additional accuracy for
BUILDUP
CONSTANT (P.871).
For example: If the buildup constant resulted in a value of 0.00154, change
the buildup constant to 0.154 and assume a value of 0.01 for P.872. Then:
0.01 x 0.154 = 0.00154 (the desired value of P.871)
7.2 Inertia-to-Current Scaling
The output of the inertia-to-current scaling function block is multiplied by NORM FIELD
REF (P.130). This sets the motor armature current required to accelerate the calculated
inertia at the desired rate, and is defined as output parameter INERTIA COMPENSATION
(P.244). Refer to figure A.15 in Appendix A of the software manual (D2-3444).
Three of the inputs to the inertia-to-current scaling function block are calculated by the
system:
•
INSTANTANEOUS INERTIA (P.230) which is the output of the instantaneous system
inertia function block (refer to figure A.14 in Appendix A of the software manual,
D2-3444).
• The output of a multiply block which uses inputs from BASE SPEED (P.017) and NORM
ROLL DIAMETER (P.131) to calibrate to rotational speed.
•
REFERENCE RATE (P.866), which is the line speed rate of change. The maximum
value is 4095 when TOP LINE SPEED (P.020) is reached in 1 second.
The remaining inputs are user-configurable.
þ
To set up the inertia-to-current scaling block:
▲
Set SYSTEM INERTIA (P.222), which is the value of JBAR as defined in section
7.1.
Range: 0.000 to 1.000 P.871 =
Range: 0.001 to 1.000 P.872 =
Range: 0.05 to 65.20 SECONDS P.222 = SECONDS