Ransburg MicroPak LECU5004 - Manual (Page 12)

MicroPak - Installation
Ransburg
9 LN-9218-00.13
C A U T I O N !
MicroPak Grounding
1. The Power Supply must be referenced to true
earth ground at only one point. (Refer to Figures
1, 2, and 3 for Grounding Connections.)
2. The feedback signals for kV and µA are devel-
oped with respect to the cascade ground. If the
cascade ground were routed only to earth ground
via the above mentioned shields, the feedback
conditioning circuitry would have to depend on
the panel ground or power supply common to
get a ground reference for the feedback signals.
This means the low level return current for these
signals would have to flow to earth ground and
back to the controller via factory ground or power
supply common. This adds large amounts of noise
to these low voltage signals.
3. A great deal of testing under high voltage corona
conditions has confirmed that this cascade ground
should be connected directly at a single point to the
signal ground plane of the MicroPak power supply
controller. This single point method maintains a
“clean” feedback signal while limiting the amount
of high frequency noise that is dumped onto the
signal ground and therefore other grounds in the
overall system, such as the PLC.
† Separate ground connections MUST be
used for grounding the part and the Power
Supply.
2. Shields from the low voltage cable must be
connected to a bus isolated from panel ground,
then by a 3/4” braid to the building steel or ground
grid if available.
3. The 24 or 28 VDC power supply common should
be connected to the factory ground input for safety,
even though they are connected to the isolated
bus via the MicroPak motherboard.
MicroPak Grounding Theory
1. The low voltage cable has a large amount of high
frequency noise on the shields and grounds from
being in proximity to the high voltage generator.
Taking these grounds directly to earth ground or a
ground grid through good high frequency conduc-
tors (braid) keeps this high frequency noise from
interfering with the low voltage control circuitry.
This is why they are isolated from panel ground.
This is consistent with standard practice for light-
ning protection. (See NFPA-70 and NFPA -780.)