Rockwell Automation 1398-DDM-xxx ULTRA 100 Series Drives Installation Manual - Manual (Page 276)

Publication 1398-5.2 – PDF 1997
E-3 Electromagnetic Compatibility Guidelines for Machine Design
One method to improve the EMC characteristics of a drive is to use an
isolation AC power transformer to feed the amplifier its input power.
This minimizes inrush currents on power-up and provides electrical
isolation. In addition, it provides common mode filtering, although the
effect is limited in frequency by the interwinding capacitance. Use of
a Faraday shield between the windings can increase the common
mode rejection bandwidth, (shield terminated to ground) or provide
differential mode shielding (shield terminated to the winding).
One alternative to AC line filters to reduce the conducted EMI
emitting from the drive. This allows nearby equipment to operate
undisturbed. In many cases an AC line filter will not be required
unless other sensitive circuits are powered off the same AC branch
circuit. The basic operating principle is to minimize the high
frequency power transfer through the filter. An effective filter achieves
this by using capacitors and inductors to mismatch the source
impedance (AC line) and the load impedance (drive) at high
frequencies.
For drives brought into use in Europe, use of the correct filter is
essential to meet emission requirements. Detailed information on
filters is included in the manual and transformers should be used
where specified in the manual.
Note: “Common mode” noise is present on all conductors referenced
to ground. “Differential mode” noise is present on one conductor ref-
erenced to another conductor.