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Description
4.2 Device description
SIRIUS 3RN2 thermistor motor protection relay
24
Manual, 10/2016, A5E34244868002A/RS-AA/001
Benefit
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Thanks to direct motor protection, overdimensioning of the motors is not necessary
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No settings are required on the SIRIUS thermistor motor protection relay.
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Semiconductor-compatible output thanks to versions with hard gold-plated contacts
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Rapid error diagnosis thanks to SIRIUS thermistor motor protection relays that indicate
wire break and short-circuits in the sensor circuit
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All SIRIUS thermistor motor protection relays have removable terminals
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All SIRIUS thermistor motor protection relays have screw-type terminals or push-in
terminals
Bimetallic switch
In some applications, bimetallic switches (e.g. Klixon, Thermoclick) are used as sensors
instead of PTC temperature sensors. Bimetallic switches are temperature and current-
dependent NC contacts and are available for different temperature ranges.
Because bimetallic switches have practically no resistance below their opening temperature,
short-circuit detection is not possible when using bimetallic switches.
A bimetallic switch can be used for versions 3RN2000 and 3RN2010 on the SIRIUS
thermistor motor protection relay.
Note
Never use bimetallic switches in applications subject to an explosion hazard!
Because of their non-standardized tripping characteristic, bimetallic switches must not be
used in applications where there is an explosion hazard. Use type A PTC sensors instead!