The VMD420-D-1 is a multifunctional voltage and frequency monitoring relay from Bender, part of the LINETRAXX® series. It is designed for 3(N)AC systems to monitor undervoltage, overvoltage, underfrequency, overfrequency, phase sequence, phase failure, and asymmetry. The device uses true RMS measurement to ensure accuracy even in harmonic‑rich industrial environments.
Technical Specifications
· Rated system voltage (Uₙ): 3(N)AC 0…500 V
· Frequency range: 10…500 Hz
· Supply voltage (Uₛ): AC 16…72 V, 15…460 Hz; DC 9.6…94 V
· Power consumption: ≤ 4 VA
· Alarm relays: Two independent changeover contacts, AC 250 V / 5 A
· Measurement accuracy (voltage): ±1.5% of full scale (50/60 Hz)
· Measurement accuracy (frequency): ±0.2% ±1 digit
· Response time (voltage): ≤ 140 ms
· Response time (frequency): ≤ 335 ms
· Operating temperature: –25 °C … +55 °C
· Mounting: DIN rail mounting
· Protection class: Terminals IP20, internal components IP30
· Order number: B73010005 (push‑wire terminals)
Key Features
· True RMS measurement – Accurate voltage monitoring even with harmonic distortion and non‑sinusoidal waveforms
· Multifunctional monitoring – Undervoltage, overvoltage, underfrequency, overfrequency, asymmetry, phase sequence, phase failure
· Two independent alarm relays – Configurable for different alarm conditions with selectable N.O./N.C. operation
· Adjustable time delays – Start‑up delay, response delay, and release delay to prevent nuisance tripping
· Fault memory – Selectable latching mode; alarm events are retained even after supply voltage failure
· Preset function – Automatically assigns basic parameters upon first connection, simplifying commissioning
· Password protection – Prevents unauthorised changes to safety setpoints
· History memory – Stores the first alarm value for diagnostic purposes
· Self‑monitoring – Continuous internal self‑test ensures operational reliability
· Internal test/reset button – Manual testing and reset without external controls
· Sealable transparent cover – Prevents unauthorised parameter changes
· LCD display – Real‑time readings and onboard menu navigation
Typical Applications
· Machine voltage protection in industrial control systems
· Generator protection (emergency and standby generators)
· Grid monitoring in distribution panels and switchgear
· Renewable energy systems (solar PV, wind power)
· Building automation and HVAC systems
· Data centre power quality monitoring
· Medical locations (IT systems in operating theatres, ICUs)
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