Siemens A&D has completed its Sirius family of 3UG4 products with three relays for level, speed and residual-current monitoring. With the level monitoring relay, the user can monitor liquids in combination with 1, 2 or 3-pole probes. The user is therefore able to react in good time before containers overflow or pumps run dry, or when leakages occur. The Sirius speed monitoring relay ensures that motors are used efficiently. Operating via external sensors, it measures the time a motor or a driven wheel needs for one revolution and responds accordingly if the speed exceeds or falls below the limits previously set. Speed monitoring relays are used, for example, for overload protection when bearings seize, belt slippage occurs or in the event of load shedding when a belt breaks. The residual-current monitoring relay used in conjunction with the 3UL22 summation current transformers protects and monitors plants. Residual-current monitoring relays are primarily used where, for example, insulation problems occur frequently due to humidity, contamination or cable damage. Due to freely selectable warning and disconnection thresholds, the monitoring relay draws attention to impending insulation problems before switching off equipment in order to protect the plant when a critical value is exceeded.
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