DC Bus Undervoltage

What does UV1 mean?

The DC bus voltage inside the drive has fallen below the trip point (e.g., 190Vdc for 240V AC input or 380Vdc for 480V AC input), which is adjustable via L2-05. Common causes include insufficient incoming AC power, excessively short acceleration times leading to voltage sag, or significant fluctuations in the input voltage quality.

Complete Troubleshooting Guide

1. 1

   Check the incoming AC power supply at the R/L1, S/L2, and T/L3 terminals to ensure voltage is within specifications, balanced, and stable.

2. 2

   Increase the acceleration time settings in parameters like C1-01, C1-03, C1-05, or C1-07 to reduce transient current demands during acceleration.

3. 3

   Inspect the power grid for voltage sags, brownouts, or excessive line impedance that might cause fluctuations, and verify transformer tap settings.

4. 4

   If applicable, check the condition of DC bus capacitors for degradation.