Supplemental Power Supply; Verify Wiring And Connections - GE Masoneilan SVI II ESD Installation And Maintenance Manual

Supplemental Power Supply

An alternative approach is to boost DCS compliance voltage using a supplemental power
supply (see Figure 87 on page 185) with split ranged SVI II ESD positioners connected in series
with the supply. It is not recommended to use supplemental supplies when Intrinsic Safety is
required. Barriers do not permit adequate voltage. Contact the DCS vendor to verify that the
output circuit is compatible with added voltage. Supplemental voltage must equal 9.0 V for
each additional SVI II ESD. Exceeding values stated in Table 35 causes damage if signal wires
are short-circuited.
Number of SVI II ESDs on a Current Loop

Verify Wiring and Connections

For split range installations some additional constraints have to be considered: the minimum
span must be 5 mA; the upper range value must be from 8 to 20 mA; the lower range values
must be from 4 to 14 mA.
Use the following procedure to ensure that SVI II ESD split range system is properly powered:
1. Connect a DC voltmeter across the input terminals.
For input current value between 4 and 20 mA, the voltage varies between 11 V and 9 V
respective.
2. Read current from the local display or with a milliammeter installed in series with the SVI II
ESD.
When voltage exceeds 11 V check that polarity is correct.
If voltage is less than 9 V and polarity is correct, voltage compliance of current source is
inadequate.
3. Connect a milliammeter in series with current signal. Verify that source can supply 20 mA
to SVI II ESD input.
If 20 mA is not attainable, see troubleshooting.
184 |
=GE Oil & Gas
Table 35 Supplemental Voltage for Split Range
1
2
3
Improperly or inadequately grounded installations can cause
NOTE
noise or instability in the control loop. The internal electronic
components are isolated from ground. Grounding the case is
unnecessary for functional purposes but grounding the case may
be necessary to conform to local codes.
Maximum Allowable Supplemental Voltage
0
9.0 VDC
18.0 VDC
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