Control Relay · Electrical Components & Switchgear
The Siemens 3RU21 is a thermal overload relay covered by a DNV type approval certificate. It is mounted on a contactor in motor control centres and control panels to protect motors against overload by monitoring motor current. It trips the contactor when current stays too high for too long, protecting motor windings from overheating.
Listed in the DNV Approval Finder at the time we recorded it. The certificate is issued by DNV, not by us; check its current status at DNV.
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