Why might the 3phase Altivar 31 drive not get Input Phase Loss fault (PHF) with one phase removed?
With the Altivar 31 drive, the input phase loss is actually detected by measuring the DC bus ripple. This is a good thing because DC bus ripple is not healthy for the DC bus capacitors. So, the drive is protecting itself from DC bus ripple rather than simply loss of voltage on an input phase. The amount of DC bus ripple that results from loss of line voltage depends on input impedance and current.