Glentek Inc. 208 Standard Street, El Segundo, California 90245, U.S.A. (310) 322-3026
59
be used to connect the drive and filter, rather than a wire.
3) The wires connecting the AC source to the filter should be shielded from, or at least
separated from the wires (or strap) that connects the drive to the filter. If the connec-
tions are not segregated from each other, then the EMI on the drive side of the filter can
couple over to the source side of the filter, thereby reducing, or eliminating the filter ef-
fectiveness. The coupling mechanism can be radiation, or stray capacitance between
the wires. The best method of achieving this is to mount the filter where the AC power
enters the enclosure. “AC Line Filter Installation” shows a good installation and a poor
installation.
When multiple power cables enter A unfiltered line can contaminate a filtered line external to the enclo-
sure. Therefore, all lines must be filtered to be effective. The situation is similar to a leaky boat. All
the holes must be plugged to prevent sinking.
If the filter is mounted excessively far from the drive, it may be necessary to mount it to a grounded
conductive surface, such as the enclosure, to establish a high frequency (HF) connection to that sur-
face. To achieve the HF ground, direct contact between the mounting surface and the filter must be
achieved. This may require removal of paint or other insulating material from the cabinet or panel.
The only reasonable filtering at the drive output terminals is the use of inductance. Capacitors would
slow the output switching and deteriorate the drive performance. A common mode choke can be used
to reduce the HF voltage at the drive output. This will reduce emission coupling through the drive back
to the AC line. However, the motor cable still carries a large HF voltage and current. Therefore, it is
very important to segregate the motor cable from the AC power cable. More information on cable
shielding and segregation is contained in the section on shielding.
DRIVE
FILTER
DRIVE
FILTER
POOR
GOOD
Figure 2- AC Line Filter Installation
Appendix G
Summary of Contents for Omega SMC9930
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