Undervoltage Alarm

Hva betyr UV ?

An Undervoltage (UV) alarm is displayed on the digital operator during a momentary power loss event, specifically after power loss but before a fault trip occurs. This indicates that the drive is actively attempting to ride through the power loss, maintaining operation as long as control power is sustained. It's a warning, not a fault that stops the drive immediately.

• Momentary dip or sag in the incoming AC line voltage (L1/R, L2/S, L3/T) lasting longer than typical grid noise but not severe enough to cause a hard fault.
• Heavy load transients on the power grid causing temporary voltage reductions that activate the undervoltage alarm threshold.
• Poorly regulated power supply or undersized distribution transformer feeding the drive, leading to voltage fluctuations.
• Loose or corroded connections in the main power circuit before the drive, causing voltage drops under load.

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1. 1

   Monitor the incoming AC line voltage at the drive's L1/R, L2/S, L3/T terminals with a power quality analyzer to identify voltage dips or sags.

2. 2

   Verify the ride-through capabilities of the drive by checking parameters related to power loss compensation (e.g., L2-01, L2-02, L2-03, L2-04), ensuring they are optimized for the application.

3. 3

   Inspect all main power wiring connections, from the facility's main disconnect to the drive's input, for tightness and corrosion.

4. 4

   If the problem is widespread, consult the facility's electrical engineer to assess the main power distribution system and transformer sizing.

5. 5

   Consider installing an Uninterruptible Power Supply (UPS) for the control circuit or a line reactor on the input of the drive to mitigate voltage fluctuations.