The IRDH275B-49327 is a high-performance insulation monitoring device from Bender, designed for unearthed AC, AC/DC, and DC main circuits (IT systems). It continuously monitors insulation resistance and is suitable for modern power systems containing rectifiers, frequency converters, thyristor-controlled DC drives, and directly connected DC components. The device complies with IEC 61557‑8.
The “B” in the type designation indicates the enhanced version, featuring a history memory with real-time clock, an RS‑485 interface (BMS protocol) for data exchange, an ISOMETER® disconnecting relay for coupled IT systems, and an isolated 0(4)…20 mA analog current output. 49327 is the hardware configuration code, representing a supply voltage of AC 88…264 V / DC 77…286 V and DIN rail mounting.
Key Features
· AMPPlus Measuring Principle – Uses Bender‘s patented AMPPlus measuring technology (European Patent EP 0 654 673 B1), automatically adapting to system leakage capacitance and DC components, reliably distinguishing between actual insulation faults and inherent system leakage capacitance.
· Automatic Adaptation to System Leakage Capacitance – Maximum permissible system leakage capacitance ≤ 500 μF, automatically optimising measurement time.
· Two Independently Adjustable Alarm Values – Alarm range 1 kΩ … 10 MΩ, allowing separate configuration of pre-warning and critical alarm.
· Two-Line LC Display – Backlit display showing real-time insulation resistance values; front-panel keys for operation.
· Alarm History Memory – Built-in memory with real-time clock stores up to 300 alarm messages with precise date and time stamps.
· RS‑485 Communication (BMS Protocol) – Galvanically isolated interface for data exchange with other Bender devices or PLCs.
· Analog Current Output – Isolated 0(4)…20 mA output for connection to SCADA systems.
· ISOMETER® Disconnecting Relay – For coupled IT systems, ensuring multiple devices operate without mutual interference.
· Connection Monitoring – Continuously monitors measuring leads and earth connection status.
· Automatic Self-Test – Continuously verifies internal measuring circuits; supports external push-button activation.
· External Test/Reset Functions – Supports connection of external push-buttons for testing and resetting.
· De-Energised System Monitoring – Independently powered; can monitor the system even when the main circuit is de-energised.
· Voltage Extension – Can be extended to higher voltages (e.g. DC 0…1760 V) using AGH coupling devices.
Technical Specifications
· Nominal system voltage (Uₙ): 3(N)AC 0…793 V; AC 0…793 V; DC 0…650 V
· Frequency range (fₙ): DC, 0.2…460 Hz
· Supply voltage (Uₛ): AC 88…264 V (47…63 Hz); DC 77…286 V
· Response value range (Rₐₙ₁ / Rₐₙ₂): 1 kΩ … 10 MΩ, two thresholds independently adjustable
· Maximum permissible system leakage capacitance: ≤ 500 μF
· Measuring principle: AMPPlus (patented adaptive measuring pulse method, European Patent EP 0 654 673 B1)
· Display: Two-line LC display with backlight
· Alarm relays: Two independent changeover contacts (Alarm 1 and Alarm 2), configurable for N/O or N/C operation
· Analog current output: 0(4)…20 mA, galvanically isolated; also provides 0…400 μA output for external kΩ display
· Communication interface: RS‑485, galvanically isolated, supporting BMS protocol
· Fault memory: Built-in storage with real-time clock; stores up to 300 date- and time-stamped alarm messages
· Disconnecting relay: Internal ISOMETER® disconnecting relay for coupled IT system operation
· Standby contact: Yes, stops insulation measurement when closed
· Operating temperature: –40 °C … +70 °C
· Storage temperature: –40 °C … +85 °C
· Protection class: Terminals IP30, enclosure IP20
· Mounting: DIN rail (35 mm standard rail)
· Weight: Approx. 0.55 kg
· Country of origin: Germany
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8
Typical Applications
· Industrial IT systems
· Medical locations (operating theatres, ICUs)
· UPS and battery systems
· Marine and offshore applications
· Coupled IT systems
· Photovoltaic and renewable energy systems
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