BENDER VMD421H-D-3 Insulation Monitor

Description

BENDER VMD421H-D-3 Insulation Monitor

Product Dimensions：

The Bender VMD421H-D-3 is a high-performance, multi-functional Voltage Monitoring Relay designed for three-phase AC systems. It is part of Bender’s advanced monitoring series, engineered to protect electrical installations and equipment against voltage fluctuations, phase failures, and frequency variations.

Product Detailed Description

The VMD421H-D-3 monitors three-phase AC systems (including those with neutral lines) for undervoltage, overvoltage, frequency variations, phase asymmetry, and phase failure. It is a digital, microprocessor-controlled device featuring an integrated LCD display that provides real-time voltage readings and an intuitive menu interface for precise parameter configuration.

The device features two separately configurable alarm relays, allowing for a two-stage warning system (e.g., pre-alarm and main alarm trip).

Technical Parameters

Product Advantages

• Comprehensive Multi-Monitoring: Replaces multiple individual relays by combining overvoltage, undervoltage, asymmetry, phase sequence, and frequency monitoring into a single compact DIN-rail device.
• True RMS Measurement: Utilizes True RMS (Root Mean Square) measuring principles, ensuring highly accurate readings even in electrical networks heavily distorted by harmonics or non-linear loads.
• Dual Alarm Relays: The inclusion of two independent output relays allows for highly flexible control strategies (e.g., Relay 1 handles non-critical load shedding on pre-alarm, while Relay 2 executes a complete system shutdown).
• Fault Memory: Features a built-in fault history memory, allowing technicians to review past alarm triggers and easily diagnose intermittent grid anomalies.
• Password Protection: Settings can be locked via a user-defined password to prevent unauthorized personal from tampering with critical safety thresholds.

Important Considerations & Precautions

• Supply Voltage vs. Monitored Voltage: Ensure that the separate supply voltage (U_s) connected to the device matches the 100–240 V AC/DC requirement. Do not mistake the monitored line inputs for the device power input.
• Phase Sequence Configuration: If your application requires mandatory clockwise phase rotation (e.g., for three-phase motors), make sure the phase sequence monitoring function is explicitly enabled in the software menu.
• Time Delay Adjustments: To avoid “nuisance tripping” caused by momentary voltage sags during the startup of large nearby motors, carefully configure the response delay time (t_{on}).
• Isolation Testing: Disconnect the monitoring relay from the circuit before performing high-voltage dielectric or insulation resistance (Megger) tests on the panel, as the test voltages can destroy the internal electronic components.

Product Applications

The VMD421H-D-3 is widely deployed across critical power distribution infrastructures:

• Backup Power Systems: Monitoring the stability of incoming utility power before a transfer switch shifts the load to an emergency standby generator.
• Industrial Motor Protection: Safeguarding heavy machinery and expensive three-phase motors from overheating or failing due to phase imbalance, phase loss, or severe undervoltage.
• Renewable Energy Plants: Ensuring that solar or wind inverter outputs match grid voltage and frequency parameters before synchronization and connection.
• Data Centers & Infrastructure: Protecting sensitive IT infrastructure and cooling systems from unstable mains grids.

Shipping Port: Xiamen, China

Payment: Bank of Chicago, Bank of Singapore

Express cooperation: fedex, DHL, UPS and your express account

Service: Professional Sales provides 24 hours /7 days online service

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