BENDER IRDH275-435 Insulation Monitoring Device

 

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Product Overview

The BENDER IRDH275-435 is an ISOMETER® insulation monitoring device (IMD) designed for IT (ungrounded) AC/DC power systems. It continuously monitors the insulation resistance between live conductors and earth to detect early ground faults.

It is widely used in critical power systems where continuity is required and tripping must be avoided at first fault.

Key Specifications

• Brand: BENDER
• Model: IRDH275-435
• Series: IRDH275 / ISOMETER®
• Type: Insulation Monitoring Device (IMD)

Monitoring Capability

• System voltage range:
  • AC: up to 793 V
  • DC: up to 650 V
• Insulation resistance range: approx. 1 kΩ to 10 MΩ
• Suitable systems:
  • AC IT systems
  • DC systems
  • AC/DC mixed systems (VFD, rectifiers)

Electrical Supply

• Supply voltage: 88–264 VAC or 77–286 VDC
• Power consumption: low power industrial monitoring device (~10–14 VA typical)

Outputs / Interfaces

• 2 × alarm relay outputs (pre-alarm + main alarm)
• Analog output (proportional insulation value)
• RS-485 communication (Modbus/BMS depending version)
• Built-in test and reset functions

Working Principle

The device injects a small measuring signal into the electrical system and evaluates the leakage path to earth:

• High insulation resistance → normal operation
• Drop in insulation resistance → warning/alarm
• Severe leakage → fault indication

It can detect:

• First ground fault in IT systems
• Leakage caused by moisture, cable damage, or equipment failure
• Faults in VFD-heavy environments

Advantages & Features

• Early detection of insulation faults (before shutdown)
• Works in AC, DC, and VFD environments
• Stable measurement even with high leakage capacitance
• Dual alarm levels (warning + trip signal)
• Communication-ready for PLC/SCADA systems
• High reliability for continuous monitoring
• Critical safety component in IT power systems

Applications

• Hospitals (medical IT power systems)
• Data centers & UPS systems
• Industrial automation plants
• Marine and offshore systems
• Mining and heavy industry
• Renewable energy DC systems
• Safety-critical electrical distribution networks

Precautions

• Only suitable for IT (ungrounded) systems
• Not for TN/TT grounded systems
• Correct setup of response threshold is critical
• High VFD leakage may require parameter adjustment
• Must follow proper wiring and shielding rules
• Incorrect configuration may cause nuisance alarms
• Installation must be done by qualified electrical engineers