The IRDH375-425 is a high‑performance 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 and provides early warning of insulation faults to ensure electrical safety and prevent system downtime. The device is powered by a low‑voltage DC supply (10.2…36 V DC), making it particularly suitable for installations where only low‑voltage DC auxiliary power is available.
The ISOMETER® measures the insulation resistance R_F, the system leakage capacitance C_e, the RMS value of the nominal system voltage U_n, as well as the residual voltages to earth (U_L1e, U_L2e). Utilising the patented AMPPlus measuring technology, the IRDH375-425 automatically adapts to specific system conditions to deliver precise and reliable insulation fault detection. With its integrated RS‑485 interface supporting multiple communication protocols (BMS, Modbus RTU, IsoData), the device can be easily integrated into higher‑level control and monitoring systems. It complies with IEC 61557‑8 and DIN EN 61557‑8, ensuring reliable safety monitoring for demanding industrial applications.
Key Features & Functions
· Patented AMPPlus Measuring Principle
The IRDH375-425 employs Bender‘s patented AMPPlus measuring technology, which provides accurate monitoring even in systems with extensive DC components and high leakage capacitances – such as those containing rectifiers, converters, thyristor‑controlled DC drives, and directly connected DC components. The AMPPlus method automatically adapts to modern power supply conditions and ensures reliable insulation fault detection in challenging operating environments.
· 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 settings 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 IRDH375-425 automatically adapts to the existing system leakage capacitance (maximum ≤ 500 µF), optimising the measurement time and ensuring dependable operation without manual adjustments. The measured system leakage capacitance value is displayed for easy on‑site diagnosis.
· Multi‑Function LC Display
Equipped with a backlit two‑line LC display, the device presents measured insulation resistance values, system leakage capacitance readings, residual voltages to earth, and the RMS value of the nominal system voltage. The display facilitates easy on‑site status checks and parameter adjustments via the front‑panel keys.
· Integrated RS‑485 Communication Interface
The device includes an electrically isolated RS‑485 interface supporting multiple protocols: BMS (Bender Measuring Device Interface) for data exchange with other Bender devices, Modbus RTU, and IsoData (for continuous data output). This enables seamless integration into central monitoring and control systems, as well as remote data acquisition.
· Automatic Self‑Test and Connection Monitoring
An automatic self‑test function continuously verifies the internal measuring circuits, system control components, and earth connections. Additionally, 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.
· Configurable Time Delays
The device features selectable start‑up delay, response delay, and delay on release to prevent nuisance alarms caused by transient conditions during system start‑up or load switching, allowing the monitoring to be tailored to the specific application.
· System Voltage and Residual Voltage Measurement
Beyond insulation monitoring, the device measures the RMS value of the nominal system voltage U_n with undervoltage/overvoltage detection capability, and also measures the residual voltages of the supply conductors to earth (L1/+, L2/– to PE), offering enhanced diagnostic information for fault analysis.
· Fault Memory
The device includes a fault memory function that can be activated via the menu. 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. The fault memory can be reset locally via the front‑panel RESET button or externally via connected push‑buttons.
· Password Protection
Parameters can be protected against unauthorised changes using an integrated password protection function, preventing accidental or unauthorised adjustments of critical settings.
· External Test and Reset Functions
External push‑buttons can be connected to perform device and connection testing, or to reset 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.
· De‑Energised System Monitoring
The device is powered by an external low‑voltage DC supply (10.2…36 V DC), allowing it to monitor systems even when the main circuit is de‑energised. This ensures continuous safety oversight during maintenance or system shutdown periods.
· Voltage Extension via Coupling Devices
The nominal voltage range can be extended using appropriate Bender coupling devices (e.g., AGH series). When used 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, 0.2…460 Hz
· Supply voltage (Uₛ): DC 10.2…36 V
· Response value range (Rₐₙ₁ / Rₐₙ₂): 1 kΩ … 10 MΩ (or 1…500 kΩ depending on configuration), independently adjustable
· Maximum permissible system leakage capacitance (Cₑ): ≤ 500 µF
· Response time: ≤ 5 s (at R_F = 0.5 × Rₐₙ and Cₑ = 1 µF)
· Measuring voltage: ≤ 40 V
· Measuring current: ≤ 220 µA
· Communication interface: RS‑485, electrically isolated, supporting BMS, Modbus RTU, and IsoData protocols
· Alarm relays: Two independent changeover contacts (K1, K2), configurable for N/O or N/C operation
· System fault relay: One changeover contact (K3), N/C operation, for device‑internal fault reporting
· 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)
· Panel cutout: 138 × 68 mm
· Dimensions (W × H × D): 144 × 133 × 72 mm
· Weight: ≤ 510 g
· Order number: B91065001
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8
· 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., PV systems, large industrial networks).
· Mixed‑voltage networks – Complex systems where AC and DC components operate within the same unearthed network.
· Coupled IT systems – Installations where multiple IT subsystems are interconnected.
· 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 or system idle states.
· Extended voltage applications – Through coupling devices, the monitoring range can be extended to higher voltages (e.g., DC 0…1760 V or 3/(N)/AC 0…7200 V) for medium‑voltage IT systems.
Translation missing: en.general.search.loading