Under-voltage monitoring relay LINETRA ® VMD420 series

over-voltagefrequencyphase sequence

Overview
The multi-functional LINETRAXX® VMD420 voltage monitoring relay monitors frequency, undervoltage, overvoltage and the voltage between two threshold values (window function) in 3(N)AC systems. Voltages are measured as r.m.s. values and the current measured value is shown continuously on the LC display. The measured value that triggered the alarm relay is stored. Adjustable response times allow adaptation to installation-specific characteristics. The device requires an external supply voltage.

Key features

• Undervoltage, overvoltage and frequency monitoring for 3(N)AC systems 0…500 V
• Selectable monitoring functions: <U, >U, <f, >f (window and limit functions)
• Asymmetry, phase failure and phase sequence monitoring
• Adjustable start-up delay, response delay and delay on release
• Adjustable switching hysteresis
• r.m.s. value measurement (AC)
• Digital measured-value display via multi-functional LC display; LEDs for Power On, Alarm 1, Alarm 2
• Measured-value memory for operating value; preset function for basic parameter assignment
• Continuous self-monitoring and internal test/reset button
• Two separate alarm relays (each one changeover contact); N/C or N/O and fault memory behaviour selectable
• Password protection for device settings; sealable transparent cover; two-module enclosure (36 mm)
• RoHS-compliant

Applications

• Monitoring voltage-sensitive machines and electrical installations
• Automatic switching on/off at defined voltage levels
• Monitoring standby and emergency power supplies
• Supply-voltage monitoring of portable loads
• Protection of three-phase motors against phase loss and phase sequence errors
• Transformer protection by detection of asymmetrical load

Variants
Type | Supply voltage Us* | Nominal system voltage Un* | Art. No.**
VMD420-D-1 | AC 16…72 V / DC 9.6…94 V, 15…460 Hz | 3(N)AC 0…500 V / 288 V, 15…460 Hz | B73010005; B93010005
VMD420-D-2 | AC/DC 70…300 V, 15…460 Hz | 3(N)AC 0…500 V / 288 V, 15…460 Hz | B73010006; B93010006

Optional accessories
Type | Art. No.
Mounting clip for screw mounting (one piece per device) | B98060008
Mounting frame XM420 | B990994

Technical specifications

• Model name: LINETRAXX® VMD420
• Measurement: r.m.s. values (AC)
• Measured ranges: nominal system voltage up to 0…500 V (3(N)AC); indication of system frequency
• Supply voltage (device): variant-dependent as listed under Variants
• Frequency range: 15…460 Hz
• Outputs: two separate alarm relays (one changeover contact each)
• Configurable behaviour: N/C or N/O operation, fault memory behaviour selectable
• Adjustments: selectable monitoring functions, adjustable switching hysteresis and delays
• Display and indicators: multi-functional LC display; LEDs for Power On, Alarm 1, Alarm 2
• Memory & testing: measured value memory; internal test/reset button; continuous self-monitoring
• Security: password protection; sealable transparent cover
• Form factor: two-module enclosure (36 mm)
• Compliance: RoHS
• Requires external supply voltage