BENDER VMD421H-D-3 Insulation Monitor

Description

BENDER VMD421H-D-3 Insulation Monitor

Product Dimensions：

The Bender VMD421H-D-3 is a multifunctional voltage and frequency monitoring relay from the LINETRAXX® series. It is designed to evaluate 3-phase AC power supplies for overvoltage, undervoltage, overfrequency, underfrequency, phase asymmetry, and phase failure in both grounded and ungrounded systems.

Product Detailed Description

The VMD421H-D-3 continuously samples RMS voltage and line frequency across 3-phase systems (3NAC). The unit features a backlit digital display for real-time parameter readouts and parameter configuration directly via front pushbuttons.

The “H” suffix denotes a wide auxiliary supply voltage range, while “-D-3” specifies its DIN rail enclosure form factor, integrated LCD display, and 3-phase voltage sensing capability.

Technical Parameters

Product Advantages

• Comprehensive Grid Monitoring: Combines voltage, frequency, asymmetry, and phase-sequence protection in a single compact 36 mm module.
• True RMS Measurement: Delivers accurate sensing even in electrical environments with distorted or non-sinusoidal waveforms.
• Flexible Adjustable Delays: Configurable start-up, response, and delay-on-release timers prevent false tripping from momentary voltage sags or switching transients.
• Clear Diagnostic Interface: Front LCD displays live values, fault memory (history of recent trips), and clear alarm status icons.
• Wide Auxiliary Range: The high-voltage supply rating (AC/DC\ 70\dots276 V) ensures operational reliability across varying control power networks.

Important Considerations (Precautions)

• Auxiliary Power Isolation: Ensure the supply voltage (U_s) matches the high-range specification (70\dots276 V). Connecting a low-voltage supply (24 V DC) directly to the auxiliary terminals will fail to power the device.
• Neutral Connection (N): When monitoring single-phase or 4-wire systems (3NAC), the neutral line must be connected correctly to enable phase-to-neutral monitoring.
• Relay Operation Logic: Configure the relay contacts for either N/C (normally closed/fail-safe) or N/O (normally open) operating principle depending on your emergency disconnect setup.
• Password Lock: Utilize the password protection feature in the menu to prevent unauthorized parameter modifications on field panels.

Product Applications

• Renewable Energy Grid Coupling: Grid tie monitoring (mains decoupling) for solar PV inverters, wind turbines, and combined heat and power (CHP) plants.
• Emergency & Backup Power: Automatic transfer switch (ATS) control panels for standby diesel generators and UPS systems.
• Industrial Motor Protection: Guarding heavy machinery against single-phasing, phase reversal, and severe voltage imbalances.
• Data Centers & Infrastructure: Power quality monitoring in critical distribution cabinets.

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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