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        • Lifecycle Status

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          Safeguarding critical electrical infrastructure, Apter Power provides reliable BENDER monitoring devices designed to prevent unexpected electrical hazards in industrial facilities.

        IRDH275B-435

        / 4.9
        1001 reviews ｜ Need a Specific Revision?
        BENDER IRDH275B-435 is a digital insulation monitor for unearthed AC, AC/DC, and DC IT systems, featuring dual alarms, RS-485 BMS communication, and isolated current output.
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        Warranty Policy
        We provide 1 year warranty for all remaining parts.
        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
        Return Notice
        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
        In the event of a defect, we will send new equipment, repair equipment or refund the purchase price based on our availability. You must contact us to obtain a return authorization and return the defective device to us within 14 days of reporting the defect.
        Shipping Mode
        Various transportation options are available in each country. Shipping methods and fees are clearly indicated on all quotations.Various transportation options are available in each country. Shipping methods and fees are clearly indicated on all quotations.
        Parts Availability
        Apter Power offers a wide range of components, products and services related to industrial automation. We also supply new products from a variety of quality manufacturers.
        How to order
        We have been working hard to update our inventory. If we have stock or parts available for new factory purchases, you can contact the order online. If we do not currently have an inventory, the displayed quantity will show "Ask". Please create an online quote or contact us by phone, fax or email to check availability.

        Technical specifications for IRDH275B-435

        • Manufacturer:
          BENDER
        • Part Number:
          IRDH275B-435
        • Product Family:
          BENDER
        • Product Type:
          Digital Ground Fault Monitor
        • Stock:
          2
        • Rated voltage:
          AC 800 V
        • Rated impulse voltage/pollution degree:
          8 kV/3
        • Supply voltage Us (see nameplate):
          AC 88…264 V*
        • Frequency range Us:
          42…460 Hz
        • Supply voltage Us (see nameplate):
          DC 77…286 V*
        • Response value Ran1 (Alarm 1) / Ran2 (Alarm 2):
          1 kΩ…10 MΩ
        • Relative uncertainty (20 kΩ…1 MΩ) (acc. to IEC 61557-8:2007-01):
          ±15 %
        • Relative uncertainty (1 kΩ…20 kΩ):
          +2 kΩ/+20 %
        • Relative uncertainty (1 MΩ…10 MΩ):
          0.2 MΩ/+20 %
        • Response time tan at RF = 0.5 x Ran and Ce = 1 μF:
          ≤ 5 s
        • Measuring time:
          see characteristic curve
        • Hysteresis (1 kΩ…10 kΩ):
          +2 kΩ
        • Hysteresis (10 kΩ…10 MΩ):
          25 %
        • Current output IRDH275B (load):
          20 mA (≤ 500 Ω)
        • Interface/Protocol IRDH275B:
          RS-485/BMS
        • Connection:
          terminals A/B
        • Cable length:
          ≤ 1,200 m
        • Software version IRDH275B:
          D159 V1.8
        • Rated contact voltage:
          AC 250 V/DC 300 V
        • Making capacity:
          AC/DC 5 A
        • Breaking capacity:
          2 A, AC 230 V, cos phi = 0.4
        • Shock resistance:
          30 g/11 ms
        • Ambient temperature (during operation):
          -40 °C…+70 °C
        • Storage temperature range:
          -40 °C…+85 °C
        • Screw mounting:
          2 x M4
        • Weight:
          0.52 kg
        • Estimated shipping dimensions:
          11.1x11.1x7.7cm
        • Tariff Code:
          8537109090
        • Country of origin:
          Germany
        • Place of shipment:
          Xiamen, Fujian, China
        By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

        More Information

        Overview Manuals Specifications Protection Application Scenarios Environmental Rating

        Features:

        • Automatically adapts to system leakage capacitance while monitoring insulation resistance across AC, AC/DC, and DC unearthed systems.
        • Combines isolated RS-485 BMS communication with configurable 0 to 20 mA or 4 to 20 mA current output for control and indication systems.
        • Dual alarm thresholds, connection monitoring, real-time alarm memory, automatic self-testing, and STANDBY control support reliable system supervision.
        Continuous insulation monitoring plays an important role in unearthed power networks where a first insulation fault should be detected before electrical reliability deteriorates further. BENDER IRDH275B-435 provides continuous supervision across industrial IT systems without requiring the network to be intentionally connected to earth. Applications can include systems using AC supplies, DC supplies, rectifiers, converters, and controlled DC drives. Automatic adaptation to leakage capacitance helps maintain dependable measurement performance as network conditions change. Dual alarm levels also give operators greater flexibility when organizing warning and maintenance actions.

        Industrial installations often require insulation data to be available beyond the local panel. BENDER IRDH275B-435 supports integration through an isolated RS-485 BMS interface and can exchange information with other compatible Bender devices across cable runs up to 1,200 m. A galvanically isolated analog current output provides another method for transferring measured insulation values to external instruments or control equipment. The internal memory and real-time clock record alarm messages with date and time information, helping maintenance personnel review insulation events after alarms occur. Remote setting of selected parameters is also possible when a COM465 communication device is added.

        Networks containing interconnected IT sections require coordinated monitoring so that multiple active insulation monitoring devices do not influence one another. BENDER IRDH275B-435 addresses such installations through the F1/F2 function input, which can disconnect the measuring circuit and place the unit into STANDBY mode. The function supports selective activation through coupling switches in line-type or ring-type arrangements. Automatic and manual self-tests add another level of operational checking by examining measuring functions, memories, system connections, and earth connections. With an operating temperature range from -40 °C to +70 °C and shock resistance of 30 g for 11 ms, the unit also supports demanding industrial operating environments.
        The IRDH275B-435 BENDER Digital Ground Fault Monitor may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL) by the manufacturer (OEM).
        BENDER IRDH275B-435 Digital Ground Fault Monitor Manuals,Datasheets,Link Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
        BENDER IRDH275B-435 Digital Ground Fault Monitor Specs

        General

        • Manufacturer BENDER
        • Model IRDH275B-435
        • Condition New Original ready stock
        • Product Family IRDH275-435,IRDH275W-435,IRDH275BW-435
        Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
        • Alarm Settings: Provides a first-level adjustable digital threshold (Alarm 1) as an early warning of system insulation degradation.
        • Power Failure Protection: Provides a second-level fault response (Alarm 2) to trigger disconnection protection before a severe short circuit to ground.
        • Frequency Converter Isolation: Built-in proprietary AMPPlus adaptive measurement technology prevents equipment malfunctions caused by harmonics from high-power frequency converters.
        • Data Traceability: Includes a historical event log with a real-time clock for accurate tracing of ground fault occurrence time and trends.
        • Marine Power: Used for ground leakage monitoring in ungrounded main propulsion systems and core busbars of cargo ships, cruise ships, etc.
        • Medical IT Power Supply: Deployed in medical isolation power supply systems in hospital Class 1.5 (or Class 2) operating rooms and ICUs to prevent micro-electric shocks.
        • Photovoltaic Energy Storage: Monitors insulation degradation in DC 0...650 V circuits of large photovoltaic inverters and high-voltage lithium battery packs.
        • Heavy Industry Paper Manufacturing: Applied to critical continuous production lines in paper mills, steel mills, etc., where interruption due to single-phase grounding is not permissible.
        • Enclosure Protection: The front panel features an IP54 industrial-grade protection design to withstand splashes of water and dust.
        • Operating Temperature: Supports a wide temperature range of -25 °C to +55 °C to adapt to the extreme harshness of industrial control cabinet environments.
        • Seismic Resistance Specifications: Passes IEC 60068-2-6 vibration test to ensure stable operation in high-vibration environments such as ships or rail transportation.
        • Insulation Withstand Voltage: Possesses a high rated insulation voltage to withstand transient electrical surges of up to several kilovolts on the power supply side.
        Description
        BENDER IRDH275B-435 monitors insulation resistance between an unearthed IT system and protective earth, making it suitable for 3(N)AC, AC/DC, and DC networks, including systems with galvanically connected rectifiers, converters, or thyristor-controlled DC drives. The monitored nominal voltage reaches AC 800 V, while suitable coupling devices can extend the operating voltage range when required. The device automatically adapts to the existing system leakage capacitance and uses the adaptive measuring pulse principle developed by Bender. Two separately adjustable response ranges from 1 kΩ to 10 MΩ allow Alarm 1 and Alarm 2 to be configured independently.

        During operation, BENDER IRDH275B-435 superimposes a microprocessor-controlled pulsating AC measuring voltage on the monitored IT system. Positive and negative measuring pulses of equal amplitude form the measuring cycle, with pulse duration influenced by system leakage capacitance and insulation resistance. When an insulation fault creates a conductive path between the IT network and earth, the resulting measuring current is evaluated by the microprocessor and converted into an insulation resistance value. The measured result appears on the two-line LC display and can also be transmitted through the isolated current output.

        BENDER IRDH275B-435 provides response times of no more than 5 seconds at RF equal to 0.5 times the selected response value and Ce equal to 1 μF. Alarm thresholds cover 1 kΩ to 10 MΩ, with relative uncertainty specified as ±15 percent from 20 kΩ to 1 MΩ, +2 kΩ/+20 percent from 1 kΩ to 20 kΩ, and 0.2 MΩ/+20 percent from 1 MΩ to 10 MΩ. Hysteresis is +2 kΩ across 1 kΩ to 10 kΩ and 25 percent across 10 kΩ to 10 MΩ. When measured insulation resistance falls below Alarm 1 or Alarm 2, the associated relay and alarm LED respond, while fault information remains available on the display.

        Communication and system integration are important functions of BENDER IRDH275B-435. The electrically isolated RS-485 interface supports the BMS protocol through terminals A and B, with a maximum cable length of 1,200 m. BMS communication permits data exchange with compatible Bender devices, while IRDH275B units can also operate with control and indication equipment such as PRC1470 version 2 or higher. The current output can be configured for 0 to 20 mA or 4 to 20 mA and is galvanically separated from the device electronics and RS-485 interface, with a load capability of up to 500 Ω.

        BENDER IRDH275B-435 also includes a real-time clock, nonvolatile parameter storage, alarm history with date and time stamps, connection monitoring, and comprehensive self-test functions. Manual self-testing can be initiated through the TEST button, while automatic testing can be configured hourly or every 24 hours. Function input F1/F2 allows the measuring connection to be internally disconnected and the unit placed into STANDBY mode, supporting coordinated monitoring in interconnected IT systems where only one active ISOMETER should remain connected to each galvanically linked network. The device operates from -40 °C to +70 °C, stores from -40 °C to +85 °C, withstands 30 g shock for 11 ms, and supports mounting with two M4 screws.
        Alternative Names
        1RDH275B-435 IRDH275B435 IRDH275-435 IRDH275W-435 IRDH275BW-435 IRDH275-427 IRDH275W-427 IRDH275B-427
        Technical notes
        Featuring the patented AMPPlus measuring principle, the IRDH275B-435 ground fault monitor delivers a precise 0(4) to 20 mA analog output and utilizes an RS-485 BMS interface for seamless multi-device communication.
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        FAQS

        The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
        VIEW ALL FAQS
        What systems can BENDER IRDH275B-435 monitor?
        BENDER IRDH275B-435 supports unearthed 3(N)AC, AC/DC, and DC IT systems, including networks containing galvanically connected rectifiers, converters, and thyristor-controlled DC drives.
        How does BENDER IRDH275B-435 measure insulation resistance?
        BENDER IRDH275B-435 applies a microprocessor-controlled adaptive measuring pulse between the IT system and protective earth. Measuring current produced by an insulation fault is evaluated to calculate the corresponding insulation resistance.
        Can BENDER IRDH275B-435 communicate with other Bender devices?
        Yes. BENDER IRDH275B-435 includes an electrically isolated RS-485 interface using the BMS protocol, with terminals A and B and a supported network cable length of up to 1,200 m.
        How does BENDER IRDH275B-435 support fault history and self-testing?
        BENDER IRDH275B-435 stores alarm messages with date and time stamps using the internal real-time clock and can run self-tests manually, every hour, or every 24 hours according to the selected configuration.
        What happens when BENDER IRDH275B-435 enters STANDBY mode through F1/F2?
        Bridging F1/F2 disconnects the measuring connections internally, stops insulation monitoring, and places BENDER IRDH275B-435 into STANDBY mode. Opening F1/F2 reconnects the monitored IT system and starts a new measuring cycle.

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