10.8.2.2
Grounding
Mark VIeS control systems separate ground into a functional earth (FE) and a protective earth (PE). The PE is intended for
power distribution functions such as JPDF, while functional earth is used for
quiet
uses such as the control electronics and
their power as on JPDS.
The JPDS board is grounded through the sheet metal bracket to the underlying back base. In most cases, this can be the
system FE.
Grounding of the JPDS takes place through metal mounting standoffs fastened to the underlying sheet metal. The ground is
used as a local reference when creating the magnitude feedback signals appearing on P2 and JA1. This is done because the
JPDS is expected to be part of the FE system in a control and mounting on a FE potential back-base is normal practice.
Note
This is different than JPDF where a PE connection is desired.
10.8.2.3
Physical Arrangement
JPDS accepts power from cables and distributes it to the JR, JS, and JT connectors. JPDS, when hosting a PPDA I/O pack, is
mounted so indicator lights on the pack are easily visible. Two JPDS boards, when used together, are mounted so that any
terminal board connections are easily accessible. The location of JPDS is not critical in a panel. Connector P1 transmits
feedback signals to a board hosting a PPDA I/O pack. Connector P2 receives feedback from other power distribution boards
and passes the signals out of P1 to the PPDA. If a feedback cable connection from JPDS P2 to another power distribution
board is planned, consideration should be given to the feedback cable routing.
JPDS is designed to accept power input from cables into the JR, JS, and JT connectors so it exhibits less mounting position
sensitivity than some other boards. The mounting surface is expected to at functional earth potential. If the board hosts a
PPDA I/O pack, consideration should be given to maintain the visibility of the indicator lights located on the top of the
PPDA. If two boards are used together, arranging them next to each other will make any needed barrier terminal strip
connections easier to use. The P1 and P2 ribbon cable headers on all of the JPDx boards are designed so the JPDS holding the
PPDA I/O pack is best located at the top of the arrangement. This allows ribbon cables to flow from one to the next, exiting
the top and entering the bottom of the next until the PPDA host is reached.
10.8.3
JPDS Application Notes
The internal wiring permits either three independent 28 V dc power buses to be maintained, or all three combined into a
single internal bus. Each bus is sized to handle 25 A. They share a common ground that is sized for 75 A. With three supplies,
it is possible to operate R, S, and T controllers and their I/O from separate power supplies. Failure of a supply can take one
controller and I/O but not affect the other two channels. There is a dedicated 28 V Diode-OR power output for the PPDA I/O
pack to avoid losing power system feedback if a channel power failure occurs.
A second method of operation has jumpers between the R, S, and T 28 V bus connection screws on TB1 and TB2. The board
provides a single highly reliable source of 28 V. Up to three supplies could power this bus with parallel operation capability
designed into the external supplies.
The screw terminals could also be used to parallel the power buses from two adjacent JPDS boards. Two boards offer the
following features:
•
Two sets of control rack output for Duplex or TMR applications using redundant supplies in the control racks, or systems
where more than three supplies are to be paralleled
•
Twelve JPDP outputs instead of six
•
Separated R, S, and T power could now have two input power supplies providing supply redundancy on each bus.
In some applications, a battery bus can be applied as a power backup. A grounded battery system can also be used as input to
this board using the screw terminals on the end of the board. This requires diodes not on JPDS to provide isolation between
the battery and internal bus. During installation or repair, any configuration performed through the barrier terminal strips must
match system documentation.
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GEH-6855_Vol_II
GEH-6855_Vol_II Mark VIeS Functional Safety Systems Volume II
Public Information
