The IRDH375B-415 is an advanced insulation monitoring device from Bender, designed for unearthed AC, AC/DC, and DC 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 complies with IEC 61557‑8 and DIN EN 61557‑8, delivering reliable safety monitoring for demanding industrial applications.
The device is panel‑mounted (control cabinet door) and incorporates Bender‘s patented AMPPlus measuring technology, which ensures accurate insulation fault detection even in systems with extensive DC components and high leakage capacitances – such as those containing rectifiers, converters, variable‑frequency drives (VFDs), and thyristor‑controlled DC drives. The “B” suffix indicates that this model includes four advanced features compared to the standard IRDH375 series: a memory with real‑time clock for date‑ and time‑stamped alarm storage, an electrically isolated RS‑485 interface supporting the BMS protocol, an ISOMETER® disconnecting relay for coordinated use in coupled IT systems, and an isolated 0(4)…20 mA analog current output. The device can also be used to monitor de‑energised systems, as it has an independent power supply.
Key Features & Functions
· Patented AMPPlus Measuring Principle – The IRDH375B-415 employs Bender‘s patented AMPPlus measuring technology, which delivers accurate monitoring even in systems with extensive DC components and high leakage capacitances. The method automatically adapts to modern power supply conditions including pure DC systems, systems with rectifiers, and those with variable‑frequency drives (VFDs).
· Two Independently Adjustable Response Values – The device features two separately adjustable alarm relays, allowing users to distinguish between pre‑warning and critical alarm. The response value ranges are independently configurable from 1 kΩ to 10 MΩ (or 1…500 kΩ depending on configuration), offering flexible configuration to meet different system safety requirements.
· Automatic Adaptation to System Leakage Capacitance – Modern power systems often generate high leakage capacitances to earth due to interference suppression measures. The IRDH375B-415 automatically adapts to the existing system leakage capacitance (maximum permissible ≤ 500 μF), optimising measurement time and ensuring dependable operation without manual adjustments. The measured system leakage capacitance value is displayed for easy on‑site diagnosis.
· Backlit Two‑Line LC Display – Equipped with a backlit two‑line LC display, the device presents measured insulation resistance values, system leakage capacitance readings, and residual voltages to earth. On‑device operation is facilitated by four front‑panel keys: INFO, TEST, RESET, and MENU.
· Memory with Real‑Time Clock – The device features built‑in alarm storage with a real‑time clock, recording all alarm messages along with precise date and time stamps. This aids in troubleshooting, maintenance scheduling, and event analysis.
· Electrically Isolated RS‑485 Interface with BMS Protocol – An electrically isolated RS‑485 interface supporting the Bender Measuring Device Interface (BMS) protocol is standard, enabling seamless data exchange with other Bender devices, central monitoring systems, and PLCs.
· Isolated 0(4)…20 mA Analog Current Output – A galvanically isolated analog current output (configurable to 0…20 mA or 4…20 mA) provides an output signal proportional to the measured insulation resistance, allowing integration with external measuring instruments, PLCs, or SCADA systems for remote monitoring.
· ISOMETER® Disconnecting Relay – An integrated disconnecting relay controlled via external terminals enables the ISOMETER® to be temporarily disconnected from the monitored IT system, an essential feature when operating multiple devices in coupled IT systems to ensure that only one remains active at any given time.
· Automatic Device Self‑Test and Connection Monitoring – An automatic self‑test function continuously verifies the internal measuring circuits, system control components, and earth connections. Connection monitoring supervises the integrity of the measuring leads. If any fault is detected, a dedicated system fault relay and LED provide immediate indication, ensuring high functional reliability.
· External Test, Reset, and Info Functions – External push‑buttons can be connected to perform device and connection testing, reset stored fault messages, or retrieve additional information such as current system leakage capacitance and device parameter settings. This enhances operational flexibility and convenience.
· 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.
· De‑Energised System Monitoring – As the device operates on an external power supply, it can monitor the system even when the main circuit is de‑energised, ensuring continuous safety oversight during maintenance or system shutdown periods.
· “W” Version for Harsh Environments (optional) – For applications requiring enhanced mechanical durability, the “W” version provides improved shock and vibration resistance, with a special varnish coating applied to the electronics to offer higher resistance against mechanical stress and moisture, making them suitable for shipboard installations, railway rolling stock, and seismic environments.
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, 0.2…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
· 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
· Measuring voltage: ≤ 40 V
· Measuring current: ≤ 220 µA
· Alarm outputs: Two independent changeover contacts (K1, K2) for Alarm 1 and Alarm 2, configurable for N/O or N/C operation
· System fault relay: One changeover contact (K3), N/C operation, for device‑internal fault reporting
· Communication interface: RS‑485, electrically isolated, supporting BMS protocol (Bender Measuring Device Interface)
· Analog output: Isolated current output, configurable as 0…20 mA or 4…20 mA
· Fault memory: Built‑in storage with real‑time clock for date‑ and time‑stamped alarm message recording
· Disconnection function: Internal ISOMETER® disconnecting relay for coupled IT system operation
· Display: Backlit two‑line LC display
· 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
· Mounting: Panel‑mounted (control cabinet door) – DIN rail mounting reference IRDH275
· Panel cutout: 138 × 68 mm
· Dimensions (W × H × D): 144 × 133 × 72 mm
· Weight: ≤ 510 g
· Order number: B91065007
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8; also complies with NEC 250.21(B) and CEC 10‑106(2) for ground detectors in ungrounded systems
· EMC: IEC 61326‑2‑4 (shock and vibration resistant)
Typical Applications
· Industrial IT systems – Insulation monitoring for AC, DC, and combined AC/DC unearthed systems incorporating rectifiers, converters, output chokes, thyristor‑controlled DC drives, variable‑frequency drives, and other power electronic loads.
· UPS systems and battery systems – Continuous monitoring of insulation integrity in uninterruptible power supplies and battery backup installations.
· 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).
· Mixed‑voltage networks – Complex systems where AC and DC components operate within the same unearthed network, requiring reliable monitoring under fluctuating operational conditions.
· Coupled IT systems – Installations where multiple IT subsystems are interconnected, requiring coordinated insulation monitoring with the integrated disconnecting relay to ensure only one ISOMETER® remains active at any given time.
· Phase‑controlled heating systems – Monitoring insulation resistance in systems using phase‑angle control for heating elements.
· Switch‑mode power supply installations – Systems with high‑frequency switched power supplies.
· De‑energised 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.
Translation missing: en.general.search.loading