The IRDH375-415 is a high-performance insulation monitoring device from Bender, designed for unearthed AC, AC/DC, and DC power systems (IT systems). It continuously monitors the insulation resistance of the main circuit, providing early warning of insulation faults to ensure electrical safety and prevent system downtime. The device is particularly suitable for modern power supply systems that incorporate rectifiers, frequency converters, thyristor‑controlled DC drives, switch‑mode power supplies, and directly connected DC components.
The IRDH375-415 is powered by a wide‑range AC/DC supply (AC 88…264 V / DC 77…286 V) and is panel‑mounted for control cabinet door installation. It complies with IEC 61557‑8 and DIN EN 61557‑8, as well as NEC 250.21(B) and CEC 10‑106(2) for ground detectors in ungrounded systems, delivering reliable safety monitoring for demanding industrial applications.
The IRDH375-415 is the standard version of the IRDH375 series. It shares the same hardware platform as the IRDH375B-415 but does not include the enhanced features of the “B” version: alarm history storage with real‑time clock, electrically isolated RS‑485 interface (BMS protocol) for data exchange with other Bender devices, ISOMETER® disconnecting relay for coupled IT systems, and isolated 0(4)…20 mA analog current output.
For applications requiring the above advanced functions, the enhanced IRDH375B-415 (order number B91065007) is available.
Key Features & Functions
· Patented AMPPlus Measuring Principle – The IRDH375-415 employs Bender‘s patented AMPPlus measuring technology, which delivers accurate insulation monitoring even in systems with extensive DC components and high leakage capacitances – including pure DC systems, systems with rectifiers, and those with variable‑frequency drives (VFDs). This patented method automatically adapts to modern power system conditions to ensure reliable readings.
· Automatic Adaptation to System Leakage Capacitance – Modern power systems often generate high leakage capacitances to earth due to interference suppression measures (such as EMI filters). The IRDH375-415 automatically adapts to the existing system leakage capacitance, optimising measurement time and ensuring dependable operation without manual adjustments. The maximum permissible system leakage capacitance is ≤ 500 μF.
· Two Independently Adjustable Response Values – The device features two separately adjustable alarm relays (Alarm 1 and Alarm 2), allowing users to distinguish between pre‑warning and critical alarm. The response value ranges are independently configurable from 1 kΩ to 10 MΩ, offering flexible configuration to meet different system safety requirements.
· Backlit Two‑Line LC Display – Equipped with a clear backlit two‑line LC display, the device presents measured insulation resistance values, system leakage capacitance readings, and other operational parameters. On‑device operation is facilitated by four front‑panel keys (INFO, TEST, RESET, MENU), enabling easy on‑site status checks and parameter adjustments.
· Built‑In Self‑Test and Connection Monitoring – An automatic self‑test function continuously verifies the internal measuring circuits, system control components, and earth connections. Connection monitoring also supervises the integrity of the measuring leads. If any fault is detected, a dedicated system fault relay and an LED provide immediate indication, ensuring high functional reliability.
· External Test and Reset Functions – External push‑buttons can be connected to perform device and connection testing, or to clear stored fault messages. This remote operability enhances convenience and safety, particularly when the device is installed in a control cabinet or hard‑to‑access location.
· 0…400 μA Analog Output for External kΩ Display – The device provides a 0…400 μA analog current output that can be connected to an external kΩ indicating instrument for remote display of the insulation resistance value.
· Fault Memory (Activatable) – The device includes a fault memory function that can be activated via the menu (latching mode). When enabled, alarm relays remain in the alarm condition and LEDs stay lit until an external reset button is pressed or the supply voltage is interrupted, helping to identify intermittent faults.
· De‑Energised System Monitoring – Because the device operates on an independent external power supply, it can monitor systems even when the main circuit is de‑energised, ensuring continuous safety oversight during maintenance or system shutdown periods.
· Voltage Extension via Coupling Devices – The nominal system voltage range can be extended using appropriate Bender coupling devices (e.g., AGH series). With coupling devices, the monitoring range can be extended to higher voltages such as DC 0…1760 V or 3(N)/AC 0…7200 V, making the device suitable for medium‑ and high‑voltage IT systems.
Technical Specifications
· Nominal system voltage (Uₙ): 3(N)AC 0…793 V / AC/DC 0…793 V; DC 0…650 V
· Frequency range (fₙ): DC, 0.3…460 Hz
· Supply voltage (Uₛ): AC 88…264 V (42…460 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 adapted measuring pulse method)
· Response time: ≤ 5 s (at R_F = 0.5 × R_an and C_e = 1 μF)
· Measurement accuracy: 1 kΩ … 1 MΩ: ±15% ±1 kΩ; 1 kΩ … 10 MΩ: ±15% ±0.1 MΩ
· Alarm relays: Two independent changeover contacts (Alarm 1 and Alarm 2), configurable for N/O or N/C operation
· System fault relay: One changeover contact for device‑internal fault reporting
· Analog output: 0…400 μA (for external kΩ indicating instrument)
· Fault memory: Activatable (latching mode); alarm signals remain until manual reset
· Self‑test: Automatic internal self‑test
· External functions: Supports connection of external test and reset push‑buttons
· Display: Backlit two‑line LC display
· Connection monitoring: Yes
· Communication interface: None (standard version)
· Operating temperature: –10 °C … +55 °C
· Storage temperature: –40 °C … +70 °C
· Climate class: According to IEC 60721‑3‑3 (class 3K5; 5…95% relative humidity, no condensation)
· Protection class: Terminals IP30, enclosure IP20
· Electromagnetic compatibility: IEC 61326‑2‑4 (shock and vibration resistant)
· Mounting: Panel‑mounted (control cabinet door); for DIN rail mounting refer to IRDH275
· Panel cutout: 138 × 68 mm
· Dimensions (W × H × D): 144 × 133 × 72 mm
· Weight: ≤ 510 g
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8; NEC 250.21(B), CEC 10‑106(2)
· Item number: B91065003
Typical Applications
· Industrial IT systems – Insulation monitoring for AC, DC, and combined AC/DC unearthed systems incorporating rectifiers, frequency converters, thyristor‑controlled DC drives, variable‑frequency drives (VFDs), and other power electronic loads.
· UPS systems and battery systems – Continuous monitoring of insulation integrity in uninterruptible power supplies and battery backup installations, ensuring electrical safety for critical equipment.
· Switch‑mode power supply installations – Monitoring insulation resistance in systems with high‑frequency switched power supplies.
· IT systems with high leakage capacitance – Installations where interference suppression filters, EMI filters, or long cable runs generate significant leakage capacitance to earth (e.g., large industrial networks, data centres).
· Pure DC and mixed‑voltage networks – Including systems with VFDs and other DC components, where reliable monitoring under fluctuating operational conditions is required.
· Systems with power electronic components – Installations with rectifiers, inverters, and other concentrated power electronic equipment.
· De‑energised / offline system monitoring – Applications where continuous insulation monitoring is required even when the main circuit is de‑energised, such as during maintenance periods.
· Extended‑voltage applications – Through coupling devices, the monitoring range can be extended to DC 0…1760 V or 3(N)/AC 0…7200 V, making the device suitable for medium‑ and high‑voltage IT systems.
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