Rockwell Automation DC3E Non-Regenerative DC Drive User Guide 1/4 - 2 HP, 115/230 VAC - Manual (Page 19)

The chassis units do not have to be earth grounded. If you
choose to ground the chassis, use a star washer beneath the
head of at least one of the mounting screws to penetrate the
anodized chassis surface and to reach bare metal.
Isolation transformer
11 Installation
ATTENTION: Distribution system capacity above the
maximum recommended system KVA requires the use
of an isolation transformer, a line reactor, or other
means of adding similar impedance to the drive power
input. Failure to observe these precautions could result
in damage to, or destruction of, the equipment
ƽ
Input isolation transformers might be needed to help
eliminate the following:
· Damaging line voltage transients from reaching the
drive.
· Line noise from the drive back to the incoming power
source.
· Damaging currents that could develop if a point inside
the drive becomes grounded.
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