The IR425-D4M1C-2 is an insulation monitoring device from Bender, designed for unearthed systems (IT systems). It continuously monitors the insulation resistance of AC/DC 0…300 V main circuits and issues an alarm signal when the insulation value falls below a preset threshold.
Technical Specifications
· Rated system voltage (Uₙ): AC/DC 0…300 V, 40…460 Hz
· Response value (Rₐₙ): 1…200 kΩ (Alarm 1 and Alarm 2, two independently adjustable thresholds)
· Supply voltage (Uₛ): AC/DC 70…300 V, 15…460 Hz
· Maximum permissible system leakage capacitance: ≤ 20 μF
· Power consumption: ≤ 4 VA
· Alarm relay contact rating: AC 250 V, 5 A (two independent changeover contacts, configurable N.O./N.C.)
· Enclosure protection: Housing IP30, terminals IP20
· Mounting: DIN rail (35 mm standard rail), width 22.5 mm
Key Features
· AMP measuring principle – Uses Bender‘s AMP (Adaptive Measuring Principle) technology, generating a pulsating measuring voltage to accurately distinguish insulation faults from inherent system capacitance. DC components present in AC/DC systems do not affect the device‘s operating characteristics.
· Two independently adjustable alarm values – Separate pre‑warning (Alarm 1) and main alarm (Alarm 2) settings, response value range 1…200 kΩ
· Multi‑function LC display – Shows real‑time insulation resistance and device parameters for on‑site diagnostics
· Connection monitoring – Continuously monitors measuring leads and earth (PE) connection integrity
· Built‑in self‑test and automatic alarm – Continuously verifies internal measuring circuits; automatically alarms on fault detection
· De‑energised system monitoring – Powered by an independent external supply; monitors the system even when the main circuit is de‑energised
· Compact design – 22.5 mm ultra‑narrow width saves space in control cabinets
Typical Applications
· Industrial IT systems (control circuits, auxiliary circuits)
· Medical locations (isolated power systems in operating theatres, ICUs)
· UPS and battery systems
· Photovoltaic and renewable energy systems (DC side)
· High‑vibration environments (railways, cranes, mining) – M1 ruggedised version
· Small AC/DC IT systems (e.g. lighting systems)
Note: This device is intended for unearthed (IT) systems only. It must not be used in earthed systems (e.g. TN/TT systems).
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