Rockwell Automation MDF-SB1304F Kinetix 6000M Integrated Drive-Motor System - Manual (Page 130)

130 Rockwell Automation Publication 2094-UM003A-EN-P - May 2012
Appendix D Kinetix 6000M System Sizing
It is important to understand that each IDM unit passes the load current for all
IDM units farther down the daisy chain. The voltage applied at each IDM unit is
dependent on voltage drop in the IDM unit control power conductors of the
hybrid cable. Therefore, the total cable length between an IDM unit and the
IPIM module affect the voltage applied to that IDM unit. Also, the number of
IDM units between an IDM unit and the IPIM module, and the cable length
between each IDM unit also affects the voltage applied to the IDM unit. An
accurate calculation requires modeling the system.
This example illustrates a simplified load estimation method. The simplifying
assumption is that all the IDM units are connected at the end of the hybrid cable
so the entire cable length supports the total IDM unit control power current.
This also means that the voltage applied at each IDM unit is the same and all
IDM units experience the maximum voltage drop. The figure below illustrates a
real system vs. the simplified system.
The specified voltage range for the IDM units is (32…44V DC). The IPIM
module output voltage specification is (40.4…41.7V DC). See the Kinetix Rotary
Motion Specifications Technical Data, publication
GMC-TD001 . The
equations below illustrate three options for estimating the IDM unit control
power load current assuming a range of 32…42V DC using the simplified system.
Steps 2 and 3 should be applied iteratively to get the best estimate, (see next step).
• Dividing the total IDM unit load power by 32V DC assumes that all the
IDM units are at the end of the total cable length, and the load current is
sufficiently high to result in the maximum allowable voltage drop at the
end of the cable. This is a very conservative method that always results in
an overestimate of the load current.
IMPORTANT Motion Analyzer version 6.000 or later contains a detailed model and
accurately predicts the IDM unit control power load current and the minimum
IDM unit control power voltage at the last IDM unit connected to each IDM unit.
IPIM
IDM 1
IDM 2
IDM 3
IDM 1 IDM 2 IDM 3
IPIM
I
1
V
1
I
L
=
∑
I
i
I
2
V
2
I
3
V
3
V
V
V
I
L