Emerson MultiFlex RTU, Инструкция по установке и эксплуатации

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4 • MultiFlex RTU Operator’s Guide 026-1706 Rev 3
2.3.1. Choosing Transformer Sizes
In most site installations, a single transformer
will power multiple devices. Choose a
transformer with a VA rating large enough to
power all devices that will be attached to it.
Table 2-2 gives the VA ratings of the MultiFlex
RTU in conjunction with other MultiFlex
boards. Refer to your site controller’s manual for
VA ratings of the other I/O boards that may be
powered by one of these transformers.
2.3.2. MultiFlex RTU Power Wiring
The MultiFlex RTU boards do not use a center
tap. Instead, the 0V terminal on the board should
be connected to a separate Earth ground.
Important! The rules that must be followed
when connecting a MultiFlex RTU board to a
transformer are different depending on
whether you have a "new style" MultiFlex
board with an isolated power supply (all
MultiFlex boards shipped after November 1,
2002) or an "old style" MultiFlex board (all
MultiFlex boards shipped before November
1, 2002).
A new-style MultiFlex board has a green power
LED located next to the 24VAC connection
terminal in the upper right corner of the circuit
board (see Figure 2-4 for reference).
If there is a green power LED next to the
connector, your MultiFlex is a new-style
MultiFlex -- refer to Section 2.3.2.1., New-Style
MultiFlex RTU Boards (with Isolated Power
Supply) for power wiring instructions.
If there is no green power LED next to the
connector, your MultiFlex is an old-style
MultiFlex -- refer to Section 2.3.2.2.,
Old-Style
MultiFlex RTU Boards No Isolated Power
Supply)
for power wiring instructions.
2.3.2.1. New-Style MultiFlex RTU Boards
(with Isolated Power Supply)
The new-style MultiFlex board can be connected
to any of the center-tapped transformers
mentioned in
Table 2-2
, provided the 0V
terminal of the board is connected to an Earth
ground.
Unit VA VAC
Center
tapped?
MultiFlex 16 6 24 Yes
MultiFlex 88,
88AO, 168, and
168AO
15 24 NO
MultiFlex RTU 15 24 NO
Table 2-2 - Device Power Requirements
Figure 2-4 - New-Style vs. Old-Style MultiFlex Board
POWER LED
New Style
MultiFlex Board
(Top Left Corner)
NO POWER LED
Old Style
MultiFlex Board
(Top Left Corner)
24 VAC
24 VAC