The isoRW425-D4W-4 is an insulation monitoring device (ISOMETER®) from Bender, specifically designed for railway applications. It monitors the insulation resistance (R mode) or insulation impedance (Z mode) of unearthed AC, AC/DC and DC main circuits (IT systems) with a rated system voltage of up to 3(N)AC, AC, AC/DC or DC 0…440 V.
The device complies with the EN 50155 railway standard and is suitable for control circuits in railway vehicles. DC components present in 3(N)AC and AC/DC systems do not affect the operating characteristics as long as a minimum load current of DC 10 mA flows. A separate supply voltage allows de‑energised systems to be monitored as well. The W version offers increased shock and vibration resistance (3K23; 3M12) and an extended operating temperature range of –40 °C … +70 °C.
Technical Specifications
· Rated system voltage (Uₙ): 3(N)AC, AC, AC/DC or DC 0…440 V, 15…460 Hz
· Supply voltage (Uₛ): AC 100…240 V (47…63 Hz) / DC 24…240 V
· Response value range (Rₐₙ₁ / Rₐₙ₂): 1…990 kΩ (two independently adjustable thresholds)
· Max. permissible system leakage capacitance (Cₑ) in R mode: ≤ 300 μF
· Max. permissible system leakage capacitance (Cₑ) in Z mode: ≤ 1 μF
· Measuring principle: R mode (insulation resistance measurement) or Z mode (insulation impedance measurement for 50 Hz or 60 Hz)
· Display: Multi‑function LCD display
· LED indicators: AL1, AL2
· Alarm output: Two independent changeover contacts (K1, K2)
· Communication interface: RS‑485 (galvanically isolated), supporting BMS, Modbus RTU and isoData protocols
· Protection class: Internal components IP30, terminals IP20
· Mounting: 35 mm DIN rail
· Operating temperature (W version): –40 °C … +70 °C
· Software version: D0418
· Standards compliance: IEC 61557‑8, DIN EN 50155, EN 45545‑2
· Order numbers: B71037000W (push‑wire terminals); B91037000W (screw‑type terminals)
Key Features
· Dual‑mode insulation monitoring: Switchable between R mode (insulation resistance) and Z mode (insulation impedance for 50 Hz or 60 Hz systems)
· Automatic adaptation to system leakage capacitance: Automatically adapts up to 300 μF in R mode
· System voltage measurement: Measures the rated system voltage (true RMS) with undervoltage and overvoltage detection
· DC residual voltage measurement: Measures L+/PE and L‑/PE
· Two independently adjustable alarm thresholds: Response range 1…990 kΩ (Alarm 1, Alarm 2)
· Device self‑test and connection monitoring: Automatic self‑test with connection monitoring
· Adjustable time delays: Start‑up delay, response delay and delay on release
· Fault memory: Activatable fault storage
· Password protection: Prevents unauthorised parameter changes
· RS‑485 communication: Galvanically isolated, supporting BMS, Modbus RTU and isoData protocols
· Selectable N/C or N/O operation: Alarm relays configurable for normally closed or normally open operation
Typical Applications
· Railway vehicle control circuits: Compliant with EN 50155
· Industrial AC control circuits: Mechanical engineering, power plants, elevators, automation systems
· AC control and auxiliary circuits: Compliant with DIN EN 60204‑1 (Electrical equipment of machines)
· AC auxiliary circuits: Compliant with DIN VDE 0100‑725
· Small AC IT systems: Lighting systems, mobile generators
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