The IR470LY-4021 is an insulation monitoring device designed specifically for unearthed systems (IT systems). It continuously monitors the insulation resistance of AC main circuits and triggers an alarm immediately when the insulation value falls below a preset threshold, preventing shutdowns caused by a second earth fault. The device operates on the DC superimposition measuring principle and is particularly suitable for pure AC systems (without frequency converters or rectifiers). It also supports offline monitoring when the main circuit is de-energised.
Technical Specifications
· Rated system voltage: AC 0…793 V, 40…460 Hz
· Supply voltage: DC 9.6…84 V
· Response value: 1…200 kΩ (adjustable, two selectable ranges)
· Alarm output: Two independent changeover contacts, AC 250 V / 5 A
· Power consumption: 3.0 VA
· Protection class: Housing IP30, terminals IP20
· Mounting: DIN rail or screw mounting
· Weight: approx. 0.36 kg
· Order number: B914048006
Key Features
· DC superimposition measurement – Accurately monitors insulation resistance of IT systems to earth
· Dual alarm thresholds – Separate pre‑warning and main alarm, independently adjustable
· Connection monitoring – Real‑time supervision of measuring leads and earth connection; flashes on interruption
· Offline monitoring – Independent power supply allows monitoring even when main circuit is de‑energised
· LED bar graph – Visual indication of current insulation level
· Fault memory – Selectable latching mode captures intermittent faults
· Self‑test and reset – TEST/RESET button on front panel; supports remote operation
· Voltage extension – Extendable to 7.2 kV with AGH coupling devices
Typical Applications
· Pure AC unearthed systems: Motors, pumps, fans, air conditioning, lighting, heating, etc.
· Industrial plants: Control circuits, motor control centres
· Mobile generators: Online or offline insulation monitoring
· Marine and offshore: Shipboard power systems
· Infrastructure: Tunnel lighting, railway signalling, emergency power supplies
· De‑energised loads: Insulation monitoring of fire pumps, valves, etc. when main power is off
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