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Why would ATV66 unit be giving an input phase loss fault?

Possibly may have low voltage on one of the input line phases. Need to verify if have proper dc bus voltage at PA and - terminals with meter and compare with what display says dc bus voltage is. Verify line power at each of the input terminals and compare with what display says line voltage is. If these voltages check ok at this points then need to verify that the voltage has reached the power board at the appropriate terminals ( should measure phase to phase voltage at J38, J39 & J40 on power board.) ( connection of measurement to the power board is made through the filter board on units ATV66D16N4 up to ATV66C19N4 so filter board is a possibility as an issue). Need to use process of elimination to determine where voltage is not present. A voltage unbalance greater than 18 - 20% will trigger fault also (Voltage unbalance is defined in NEMA ICS 7. Additionally after have checked all this and if ok then need to verify if possibly have open diode by checking the diode bridge according to Service and Troubleshooting manual VD0C06S701 or VD0C06S702 which shows how would check between the + & - terminals to each line terminal L1, L2, L3 making sure to check + lead of meter to + & - and each line and then rotate with - lead of meter to + & - terminals and each line terminal. Should get infinite in one direction and no resistance in other for each set of checks which will help determine if issue is open diode.

CTA-ID : 13201
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