Rockwell Automation 9329 Drive Application Software Inertia Comp Imperial Units - Manual (Page 10)

FM – Inertia Compensation
Drive Application Software – page 10 of 28
If any signal scaling is required to interface the Function Module into the user application, the
user may use the main routine for this programming. Note; any scaling for inputs to the
routines should be done before the JSR and any scaling applied to the return values from the
routines should be done after the JSR.
4.3 JCalc Routine
Material width, material density and diameter are used to calculate the roll inertia.
The roll inertia is reflected to the motor shaft by dividing by the gear ratio squared.
Total reflected inertia is calculated by adding the reflected roll inertia to the minimum
empty core reflected inertia. The total reflected inertia is then normalized two different
ways.
The first method of normalization divides total reflected inertia by minimum empty
core reflected inertia. This results in a normalized inertia that is 1.0 per-unit at core
and greater than 1.0 per-unit as the roll diameter increases.
The second method of normalization multiplies the total reflected inertia by motor
base speed and then divides by rated motor torque. This results in inertia with units
of seconds. Inertia, normalized this way, represents the time to accelerate the total
connected inertia from zero to motor base speed with rated motor torque applied.
Input Parameters
Name Type Range Description
1 JEC_lbft2 REAL NA Minimum Empty Core Reflected Inertia
2 Density_lbft3 REAL NA Material Density
3 BuildUpRatio REAL NA Normalized Diameter
4 Constant_RPMperFPM REAL NA Calibration Constant
5 Width_in REAL 5.0 to 500.0 Material Width
6 GearRatio REAL NA Gear Ratio
7 MtrSpdBase_RPM REAL NA Motor Base Speed
8 MtrTrqRated_lbft REAL NA Motor Rated Torque
Return Parameters
Name Type Range Description
1 WeightRoll_lb REAL NA Roll Weight
2 Jroll_lbft2 REAL NA Roll Reflected Inertia
3 J_lbft2 REAL NA Total Reflected Inertia
4 J_sec REAL NA Total Reflected Inertia
5 J_PU REAL NA Total Reflected Inertia
4.3.1 JEC_lbft2
This input parameter is the minimum empty core reflected inertia in pound/feet 2 .
Usage – Set equal to the inertia of the machine at empty core in pound/feet2.
4.3.2 Density_lbft3
This input parameter is the material density pound/feet3.
Usage – Set equal to the material density in pound/feet3.
4.3.3 BuildUpRatio
This input parameter is the build-up ratio or normalized roll diameter.
Usage – From the Diameter Calculator Function Module return parameter of the
same name.