The IRDH275B-49335 is a high-performance insulation monitoring device from Bender, designed for unearthed AC, 3AC, AC/DC, and DC power systems (IT systems). It continuously monitors the insulation resistance of the main circuit and is suitable for modern power supply systems that contain rectifiers, frequency converters, thyristor-controlled DC drives, and directly connected DC components. The device complies with IEC 61557‑8.
Technical Specifications
· Rated system voltage (Uₙ): 3AC/AC 0…793 V; DC 0…650 V
· Response value (Rₐₙ): 1 kΩ … 10 MΩ (two independently adjustable thresholds)
· Supply voltage (Uₛ): AC 88…264 V; DC 77…286 V
· Power consumption: 8.0 VA
· Relay contact rating: AC 250 V, 5 A
Key Features
· AMPPlus Measuring Principle – Uses Bender‘s patented AMPPlus measuring technology, delivering accurate insulation monitoring even in systems with extensive DC components and high leakage capacitances.
· Automatic Adaptation to System Leakage Capacitance – Automatically adapts to the existing system leakage capacitance (maximum permissible ≤ 500 μF), optimising measurement time without manual adjustments.
· Two Independently Adjustable Response Values – Features two separately adjustable alarm relays, each configurable from 1 kΩ to 10 MΩ.
· Two-Line LC Display – Equipped with a clear two-line LC display with backlight, showing real-time insulation resistance values.
· Alarm Indicators – Front panel includes three LED indicators: AL1 LED (pre-warning), AL2 LED (critical alarm), and System Fault LED.
· Built‑In Self‑Test and Connection Monitoring – Automatic self-test continuously verifies internal measuring circuits and system components. The TEST button can manually trigger a test.
· External Test and Reset Functions – Supports connection of external test and reset push-buttons.
· Standby Contact – Includes a standby contact. When the contact is closed, insulation measurements stop.
· De‑Energised System Monitoring – Powered by an independent external supply, the device can monitor the system even when the main circuit is de‑energised.
· Voltage Extension via Coupling Devices – Using Bender AGH series coupling devices, the nominal system voltage range can be extended to higher levels.
· History Memory with Real-Time Clock – Stores all alarm messages with precise date and time stamps.
· RS‑485 Communication Interface (BMS Protocol) – Electrically isolated RS‑485 interface for data exchange with other Bender devices.
· ISOMETER® Disconnecting Relay – Allows the device to be temporarily disconnected from the monitored IT system via an external control signal.
· Isolated 0(4)…20 mA Analog Current Output – Provides a signal proportional to the measured insulation value for connection to PLCs or SCADA systems.
Standards Compliance
· IEC 61557‑8, DIN EN 61557‑8
Typical Applications
· Industrial IT systems
· Medical locations (operating theatres, ICUs)
· Marine and offshore applications
· UPS and battery systems
· Photovoltaic and renewable energy systems
· Coupled IT systems
· Extended voltage applications (with AGH coupling devices)
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