Sirius Series 3RU

Product Details

Sirius Series 3RU

Order No: 3RU11..-…..

The 3RU11 thermal overload relays up to 100 A have been designed for inverse-time delayed protection of loads with normal starting against excessive temperature rises due to overload or phase failure. An overload or a phase failure result in an increase of the motor current beyond the set rated motor current. Via heating elements, this current rise heats up the bimetal strips inside the device which then bend and as a result trigger the auxiliary contacts by means of a tripping mechanism. The auxiliary contacts then switch off the load by means of a contactor. The break time depends on the ratio between the tripping current and current setting Ie and is stored in the form of a long-term stable tripping characteristic curve.

The “tripped” status is signaled by means of a switch position indicator. Resetting takes place either manually or automatically after a recovery time has elapsed. The 3RU11 thermal overload relays are suitable for operation with frequency converters. Please refer to the instructions in the reference manual entitled

The devices are manufactured in accordance with environmental guidelines and contain environmentally-friendly and reusable materials. They comply with all important worldwide standards and approvals.


The 3RU11 thermal overload relays have been designed for the protection of three-phase and single-phase AC and DC motors. If single-phase AC or DC loads are to be protected by the 3RU11 thermal overload relays, all three bimetal strips must be heated. For this purpose, all main current paths of the relay must be connected in series.