Tension-to-current scaling, 2 tension-to-current scaling – Rockwell Automation WebPak 3000 DC Drive Application Workbook Version 1.1 User Manual
Page 58
10-2
WebPak 3000 DC Drive Application Workbook, Version 1.1
•
SPEED
CROSS
OVER
(P.133), which is the bandwidth of the speed loop. This
parameter is one of the outputs calculated by the speed loop gain profiler block.
The remaining inputs are user configurable.
þ
To configure the gain profiler block:
▲
Set
TEN
PROFILER
ENABLE
(P.878). The choices are:
ENABLE
- The value of
TEN
PI
KP
OUT
(P.879) is the output of the gain profiler
block. (
TEN
PI
KP
OUT
(P.879) is the value of the proportional gain applied to
the current major loop regulator
PI
block.) Set P.878 to
ENABLE
for all variable
diameter applications.
DISABLE
- The value of
TEN
PI
KP
OUT
(P.879) is
TEN
PI
PROP
GAIN
(P.841).
▲
Set
OCL
TYPE
(P.818) to
CASCADE
. (Setting P.818 to
PARALLEL
is not
recommended for most variable diameter applications.)
▲
Set
TEN
PI
PROP
GAIN
(P.841) using the following calculation:
P.841 = LIMBAR / (2 X JBAR X FBAR)
where:
•
LIMBAR
=
MAXIMUM
CURRENT
(P.007) / 100
•
JBAR
=
SYSTEM
INERTIA
(P.222)
•
FBAR
=
GEAR
IN
SPEED
(P.011) /
BASE
SPEED
(P.017)
For a variable diameter application, the results of speed loop self-tuning with a
core diameter connected load should yield a value for
JBAR
, 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))
Total Inertia = Motor Inertia + (Core Inertia / Gear Ratio
2
)
Note that self-tuning will overwrite any manual entry for
JBAR
.
10.2 Tension-to-Current Scaling
TEN
TO
CURRENT
OUT
(P.876) is the calculated output of the tension-to-current scaling
block, which correlates rated tension in engineering units to motor current. Refer to
figure A.18 in Appendix A of the software manual (D2-3444). P.876 modifies the value
of the setpoint
TENSION
DEMAND
(P.844).
Rated Tension (lb) = Motor HP x 33000 / Line Speed in FPM
However, the relationship between rated tension and motor full load current is
impacted by motor design and machine design characteristics. Current regulated
applications, especially variable diameter applications, that use a motor with both
armature and field control require proper armature current scaling to maximize drive
control.
Range:
ENABLE
,
DISABLE
P.878 =
Range:
CASCADE
,
PARALLEL
P.818 =
&$6&$'(
Range: 0.001 to 32.767
P.841 =