Brochure/Catalogue

Glossary
Nominal switching current –
load side
The permitted load current of a relay contact or semiconductor contact when in
continuous operations.
Nominal switching voltage –
load side
The switching voltage that a relay contact or semiconductor contact uses in
relation to its application.
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Output-current loop-powered Output loop powered 2-wire transmitters have a 4 – 20 mA output. The
transmitter is supplied with power via the current loop on the output side. A
typical loop consists of a regulated DC power supply, the 2-wire transmitter and
a receiving device.
Overvoltage category The overvoltage categories are described in DIN EN 60664-1. The category
dictates the insulation clearance gaps required. Category III is the default
specication (EN 50178).
• Overvoltage category I
Devices that are intended to be connected to the permanent electrical building
installation. The measures for limiting transient surge voltages to the proper
level are taken outside of the device. The protective mechanisms can either be
in the permanent installation or between the permanent installation and the
device.
• Overvoltage category II
Devices that are intended to be connected to the permanent electrical building
installation (such household appliances or portable tools).
• Overvoltage category III
Devices that are a part of the permanent installation and other devices where
a higher degree of availability is required. This includes the distributor panels,
power switches, distribution systems (including cable, busbars, distributor
boxes, switches and outlets) that are part of the permanent installation,
devices intended for industrial use, and devices that are continually connected
to the permanent installation (such as stationary motors).
• Overvoltage category IV
Devices that are intended to be used on or near the power feed in a building’s
electrical installation – ranging from the main distribution to the mains power
system. This includes electrical meters, surge protection switches and ripple
control equipment.
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Technical appendix/Glossary
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