The IR475LY-4 is an insulation monitoring device from Bender, part of the A-ISOMETER® series, designed for unearthed systems (IT systems). It continuously monitors the insulation resistance of AC or DC main circuits and triggers an alarm when the insulation value falls below a preset threshold, ensuring the continuity and safety of the power supply. The device complies with IEC 61557‑8.
Technical Specifications
· Rated system voltage (Uₙ): 3AC/AC 0…793 V; DC 0…480 V
· Supply voltage (Uₛ): AC 230 V, 50/60 Hz
· Response value (Rₐₙ): Adjustable
· Power consumption: 3.5 VA
· Alarm output: Two independent changeover contacts, AC 250 V / 5 A
· Data sheet: 106005
· Order number: B91 1068038
Key Features
· Insulation monitoring: Continuously monitors the insulation resistance of the IT system to earth; alarm relay switches and alarm LED lights up when the insulation value falls below the set response value
· Dual alarm thresholds: Two independent alarm relays for pre‑warning and main alarm management
· LED status indication: Front‑panel LEDs clearly indicate device operating status and alarm condition
· Connection monitoring: Continuously monitors the measuring leads and earth connection to ensure measuring circuit integrity
· Self‑test and reset: Supports local manual testing and reset for easy on‑site maintenance and function verification
Typical Applications
· Industrial IT systems
· Power plants, substation auxiliary systems
· Marine and offshore applications
· Wind turbine control systems
· Medical locations (operating theatres, ICUs) – isolated power systems
· Unearthed AC/DC systems
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