Input phase loss is one of the common faults during the operation of frequency converters. For Eurotherm frequency converters, an input phase loss fault is displayed as ERR/FU12 on the operation panel. The causes and handling methods for input phase loss are as follows:

1. Abnormal three-phase power input: Check and resolve issues in the peripheral circuit.

2. Abnormal drive unit, lightning protection board, main control board, or rectifier bridge: Seek technical support.