The IR470LY‑4021 is an insulation monitoring device designed for unearthed systems (IT systems). It superimposes a DC measuring voltage onto the system to continuously monitor the insulation resistance of AC main circuits. When the insulation value falls below a preset threshold, the device triggers an alarm, allowing the first earth fault to be detected before a second fault causes a dangerous short circuit or equipment shutdown. This device is particularly suitable for pure AC systems without significant DC components or high leakage capacitance. The main circuit voltage can be up to 793 V, extendable to 7.2 kV with coupling devices.
Technical Specifications
· Rated system voltage (Uₙ): AC/3(N)AC 0…793 V, 40…460 Hz (extendable to 7.2 kV with coupling devices)
· Supply voltage (Uₛ): DC 9.6…84 V
· Response values (Rₐₙ₁ / Rₐₙ₂): 1…200 kΩ, two independently adjustable thresholds
· Max. permissible system leakage capacitance (Cₑ): ≤ 20 μF
· Measuring voltage (Uₘ): ≤ 40 V
· Max. measuring current (Iₘ): ≤ 200 μA
· Response time: In the 10…200 kΩ range, at R_F = 0.5 × Rₐₙ and Cₑ = 1 μF, ≤ 15 s
· Alarm outputs: Two independent changeover contacts (K1, K2), AC 250 V / 5 A
· Power consumption: ≤ 4 VA
· Protection class: Housing IP30, terminals IP20
· Mounting: DIN rail (35 mm) or screw mounting
· Dimensions (W × H × D): approx. 70 × 99 × 73 mm
· Weight: ≤ 0.36 kg
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8
Key Features
· DC superimposition measurement: Continuously monitors insulation resistance of IT systems (Uₘ ≤ 40 V, Iₘ ≤ 200 μA), largely unaffected by system leakage capacitance
· Two independently adjustable alarm thresholds: Pre‑warning (Alarm 1) and main alarm (Alarm 2), adjustable from 1 kΩ to 200 kΩ
· Connection monitoring: Continuously supervises measuring leads and earth connection; alarm LED flashes on interruption
· Offline monitoring: Powered by an independent external supply; monitors even when the main circuit is de‑energised
· LED bar graph: Visual indication of insulation level
· External instrument output: 0…400 μA analogue output for remote kΩ meter
· Self‑test and reset: Built‑in TEST/RESET button; supports external push‑buttons for remote operation
· Selectable fault memory: Latching mode stores alarm messages until manual reset
· Voltage extension: With AGH coupling devices, rated voltage can be extended to 7.2 kV
Typical Applications
· Pure AC unearthed systems (motors, pumps, fans, air conditioning, lighting, heating, etc.)
· Industrial plant control circuits, motor control centres (MCC)
· Online and offline insulation monitoring of mobile generators
· Marine and offshore power systems
· Tunnel lighting, railway signalling, emergency power supplies
· Offline insulation monitoring of de‑energised loads (fire pumps, valves, etc.)
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