BENDER LINETRAXX ® VMD420 Three phase Voltage Frequency Monitor

Classification of mechanical conditions (IEC 60721):

Fixed use (3M11)

Transportation (2M4)

Long term storage (1M12)

Optional version (Option "W"): Designed for special climate environments, allowing condensation and freezing during fixed use (climate classification 3K23), mechanical condition classification 3M12, suitable for extreme scenarios such as high humidity and low temperature.

（5） Wiring parameters

The device supports two wiring methods: screw terminals and push in terminals. The specific wiring requirements are as follows:

Screw terminal:

Rigid wire: 0.2... 4 mm ² (AWG 24... 12)

Flexible wire: 0.2... 2.5 mm ² (AWG 24... 14)

Two rigid/flexible wires with the same cross-section: 0.2... 1.5 mm ² (AWG 24... 16)

Wire stripping length: 8-9 mm

Tightening torque of terminal screw: 0.5... 0.6 Nm

Push in terminal:

Rigid wire: 0.2... 2.5 mm ² (AWG 24... 14)

Flexible wire without cold press joint: 0.75... 2.5 mm ² (AWG 19... 14)

Flexible wire with cold press joint: 0.2... 1.5 mm ² (AWG 24... 16)

Wire stripping length: 10mm

Terminal opening force: 50 N

Test opening diameter: 2.1 mm

（6） Other physical and installation parameters

Project parameter specifications

Continuous operation in working mode

Installation method at any position (guide rail/screw)

Protection level (internal components/terminals) IP30/IP20 (DIN EN 60529)

Shell material polycarbonate

Flame retardant grade UL94 V-0

Rail installation standard IEC 60715

Screw installation requirements: 2 x M4 screws+fixing clip

Shell dimensions (width x height x depth) 36 mm x 93 mm x 90 mm

Weight ≤ 150 g

Working principle

（1） Basic workflow

After the device is connected to the external power supply voltage (A1, A2 terminals), the start delay (t) starts timing. During this stage, fluctuations in voltage and frequency will not affect the switching status of the alarm relay, ensuring stable device startup.

After the startup delay is over, the device enters the normal monitoring state, collects the voltage and frequency signals of the monitored system through terminals L1, L2, L3, and N, and calculates the true effective value and related parameters in real time.

When the monitoring parameters exceed (or fall below) the set response value, the response delay (ton1/2) of the corresponding alarm channel is activated; If the parameter remains in an over limit state during the response delay period, the corresponding alarm relay (K1/K2) will activate and the corresponding alarm light (AL1/AL2) will light up after the response delay ends.

After the alarm is triggered, if the monitoring parameters return to the release value (response value ± switching delay), the release delay (toff) will be activated; After the release delay is completed, the alarm relay resets and the alarm light goes out.

If the fault memory function is enabled, the alarm relay will remain in the alarm state until the reset button (R) is pressed to clear the alarm; If set to continuous fault memory mode, the alarm state will still be retained even if the power supply is interrupted.

（2） Preset function (PrE run)

After the device is first connected to the power supply, it automatically starts the preset function, detects the rated voltage (Un) of the system, and automatically configures the response values for undervoltage, overvoltage, underfrequency, and overclocking based on the detection results.

If no effective rated voltage is detected during the preset process (beyond the normal voltage range), the device will set the response value to the minimum or maximum limit value, and the display screen will show "AL not SET".

When no button is pressed, the device will cycle to search for the rated voltage (continuous PrE run); If any button is pressed, the search process will be interrupted and the "AL not SET" prompt will disappear. At this time, the response parameters need to be manually configured through the menu.

When the frequency monitoring function is enabled, the preset function will automatically store the rated frequency of the current system and configure the corresponding underfrequency and overfrequency response values.

（3） Line protection requirements

According to the IEC 60364-4-43 standard, it is recommended to install 6A fuses for overcurrent protection in the equipment circuit; If the equipment is powered by the IT system, fuses need to be installed on both power lines to ensure power supply safety.

Typical application scenarios

Voltage sensitive equipment monitoring: used for power supply circuits of precision instruments, PLC controllers, industrial automation equipment, and other equipment that are sensitive to voltage fluctuations. Real time monitoring of voltage and frequency changes to avoid equipment damage or data loss caused by undervoltage, overvoltage, and frequency abnormalities.

Mechanical equipment start stop control: Based on the set voltage threshold, automatically control the start stop of machinery and production equipment. For example, when the power supply voltage returns to the normal range and stabilizes for a period of time, the equipment will automatically start; When the voltage is abnormal, promptly cut off the power supply of the equipment to protect it from impact.