Description
1. At-A-Glance Executive Brief
- Model: IRDH275BM-727 (Part No. B91065120)
- Brand: Bender
- Part Type: ISOMETER® Insulation Monitoring Device (IMD)
- Lifecycle Status: Mature / Legacy Support Line
- Weight: 0.52 kg
- Core Protocol: RS-485 / BMS (Bender Measuring Device Interface)
2. Technical Introduction
An undetected insulation breakdown or ground fault in an unearthed medium-voltage (IT) power system can trigger unexpected equipment shutdowns, severe arc flash hazards, and major safety liabilities.
The Bender IRDH275BM-727 is an advanced A-ISOMETER insulation monitoring device designed to monitor ungrounded AC, DC, and combined AC/DC systems up to 15.5 kV when paired with appropriate AGH-series coupling units. Utilizing the patented AMPPlus measuring principle, it accurately detects symmetrical and asymmetrical insulation faults even in complex networks featuring high system leakage capacitances and heavy frequency-converter drives. Deploying this unit ensures continuous plant safety compliance and rapid fault localization before a secondary earth fault triggers an emergency system trip.
Engineer’s Takeaway: Procuring an original Bender IRDH275BM-727 guarantees direct wiring and protocol compatibility with legacy monitoring panels, eliminating the need for complete safety system rewiring during maintenance replacements.
3. Core Technical Specifications
| Parameter | Value |
| Manufacturer | Bender |
| Model / Ordering Code | IRDH275BM-727 (B91065120) |
| Nominal System Voltage (U_n) | Up to AC 800 V (Direct) / Up to 15.5 kV via AGH series coupling units |
| Supply Voltage (U_s) | AC 19.2…55 V / DC 19.2…72 V |
| Response Values (Alarm 1 / 2) | 100 k\Omega to 10 M\Omega (Separately adjustable) |
| Measuring Principle | AMPPlus (patented) |
| Communication Interface | Galvanically isolated RS-485 / BMS protocol |
| Output Relays | 2 changeover contacts (Alarm 1, Alarm 2 / System Fault) |
4. Field Engineer’s Tech Notes
- Coupling Device Matching: Ensure the IRDH275BM-727 is paired strictly with the correct system-rated coupling device (such as the AGH675S series). Mismatching the insulation coordination or voltage rating of the coupling network will skew resistance measurements and can damage internal measuring circuits under high-voltage transients.
- Leakage Capacitance and Adaptation Time: The device automatically adapts to system leakage capacitances. When commissioning on extensive cable networks, verify that the initial measuring cycle completes without throwing false parameterization errors caused by transient charging currents during startup.
5. Adaptive QA & Testing Protocol
Every unit undergoes comprehensive bench testing prior to dispatch. For the Bender IRDH275BM-727, our technicians inject precise resistance steps using specialized insulation simulation boxes to verify trip thresholds on both Alarm 1 and Alarm 2 changeover contacts. We test auxiliary power supply tolerances across DC 19.2–72V and perform node handshake validations on the RS-485 BMS communication port. Functional test reports or pre-shipment video verification can be provided upon request.
6. Buyer’s FAQ
- Are these units supplied as New Surplus or refurbished?We stock factory-sealed New Surplus (NSFP) as well as fully bench-tested, static-safe refurbished units. Condition status is explicitly noted on every official quote.
- What warranty coverage comes with this part?All replacement insulation monitors are backed by a standard 12-month operational warranty from the invoice date.
- How fast can this device ship to minimize plant downtime?In-stock items ship same-day via priority air courier services to international destinations, reducing critical path delay during urgent maintenance windows.
- Is this exact model a direct drop-in replacement for older IRDH275 hardware revisions?Yes, the IRDH275BM-727 maintains exact terminal dimensions and menu structures for seamless physical and electrical replacement in legacy Bender-monitored distribution panels.
