Vega VEGAPULS 21 - Connecting to power supply; Connection preparation and safety

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5 Connecting to power supply
VEGAPULS 21 • Two-wire 4 … 20 mA/HART
58351-EN-191014
5 Connecting to power supply
5.1 Preparing the connection
Always keep in mind the following safety instructions:
•
Carryoutelectricalconnectionbytrained,qualiedpersonnel
authorised by the plant operator
•
If overvoltage surges are expected, overvoltage arresters should
be installed
Warning:
Only connect or disconnect in de-energized state.
Thedataforpowersupplyarespeciedinchapter"Technical data".
Note:
Power the instrument via an energy-limited circuit (power max. 100 W)
acc. to IEC 61010-1, e.g.
•
Class 2 power supply unit (acc. to UL1310)
•
SELV power supply unit (safety extra-low voltage) with suitable
internal or external limitation of the output current
Keepinmindthefollowingadditionalfactorsthatinuencetheoperat-
ing voltage:
•
Lower output voltage of the power supply unit under nominal load
(e.g. with a sensor current of 20.5 mA or 22 mA in case of fault)
•
Inuenceofadditionalinstrumentsinthecircuit(seeloadvaluesin
chapter "Technical data")
Use cable with round cross section for instruments with housing and
cablegland.Toensurethesealeectofthecablegland(IPprotection
rating),ndoutwhichcableouterdiameterthecableglandissuitable
for.
The instrument is connected with standard two-wire cable. If electro-
magnetic interference is expected which is above the test values of
EN 61326-1 for industrial areas, screened cable should be used.
Note:
Screened cable generally necessary in HART multidrop mode.
Note:
If the temperatures are too high, the cable insulation can be dam-
aged. Hence keep apart from the ambient temperature also the self-
heating of the instrument for the temperature resistance of the cable
in the connection compartment in mind
2)
.
Metric threads
In the case of instrument housings with metric thread, the cable gland
is screwed in at the factory. It is sealed with plastic plugs as transport
protection.
Safety instructions
Voltage supply
Connection cable
Cable gland
2)
 Withanambienttemperature≥50°C(122°F)theconnectioncableshould
besuitableforatemperaturewhichisatleast20°C(36°F)higher.