Description
Bender IRDH275B-435
Technical Specifications
- Monitoring object: Unearthed IT system ground insulation
- Measuring range: 1 kΩ to 10 MΩ
- System voltage: AC 0 to 793 V / DC 0 to 893 V
- Alarm: Two-stage pre-alarm and main alarm relay output
- Relay contact rating: AC250 V 5 A / DC30 V 5 A
- Supply: AC115 to 230 V, 50/60 Hz
- Power consumption: Approx. 4 VA
- Display: LCD showing insulation resistance
- Temperature: -20 °C to +55 °C
- Storage: -30 °C to +70 °C
- Humidity: 5 % to 95 %, non-condensing
- Protection: IP40 (front)
- Installation: DIN rail
- Certifications: CE, VDE
Functional Features
- Continuous monitoring of unearthed system ground insulation resistance
- Two-stage pre-alarm and main alarm relay outputs
- LCD direct display of current insulation resistance
- Adaptive for DC, AC, and mixed-voltage systems
- Built-in test signal generator actively injecting test signal
- Relay contact alarm output
- Front panel LEDs for power, normal, and alarm
- Push-button setting of alarm threshold and system voltage
- High measurement accuracy unaffected by system capacitance
- DIN rail mounting for easy cabinet integration
Application Scenarios
- Hospital operating room and ICU IT unearthed system insulation monitoring
- Industrial unearthed distribution system insulation monitoring
- UPS system insulation monitoring
- Photovoltaic inverter DC side insulation monitoring
- Ship and rail transit unearthed system insulation monitoring
- Data center IT system insulation monitoring
Materials and Construction
- Housing: Flame-retardant engineering plastic
- Front panel: LCD and push buttons
- PCB: FR4 board
- Core: Test signal generator and measurement circuit
- Relay: Industrial electromagnetic relay
- Terminals: Screw-fastened terminals
- Passive components: Resistors, capacitors, TVS diodes
Structural Features
- Narrow DIN rail plastic housing, 35 mm rail snap-mount
- Front panel LCD, push buttons, status LEDs
- Side terminals for supply and relay output
- Internal partitions between power, measurement, and output areas
- Fanless natural convection
- Sealed front panel for humid environments
Working Principle The instrument connects to the unearthed system via L+ and L- terminals; an internal test signal generator injects a low-frequency test voltage to ground. The measurement circuit detects voltage drop across ground insulation resistance caused by test current and computes current resistance. The LCD displays resistance; when resistance falls below pre-alarm threshold, pre-alarm relay operates; below main alarm threshold, main alarm relay operates. LEDs synchronously indicate alarm status. AC115 to 230 V supplies operating power.
Installation Requirements
- Snap-mount on 35 mm DIN rail
- Connect L+ and L- of the monitored system
- Route alarm relay contacts to external alarm circuit
- Connect AC115 to 230 V supply
- Reliably ground PE reference
- Cabinet temperature -20 °C to +55 °C
- Set system voltage and alarm thresholds after power-up
Precautions
- Monitored system must be unearthed IT; do not connect to grounded TN systems
- Set alarm threshold per system requirements
- Do not parallel other insulation monitors on the same system
- Relay contacts must not exceed AC250 V 5 A
- Periodically push button to test alarm function
- Store spares in dry environment
