GE AF-650 GP Operating Instructions Manual page 88

With a phase loss, the current waveform of the remaining phases would take on the appearance shown below.
Illustration 6.5: Input Current Waveform with Phase Loss.
Always verify the condition of the input voltage waveform before forming a conclusion. The current waveform will follow the voltage waveform. If the voltage
waveform is incorrect proceed to investigate the reason for the AC supply problem. If the voltage waveform on all three phases is correct but the current waveform
is not then the input rectifier circuit in the frequency converter is suspect. Perform the static soft charge and rectifier tests.
High Power Service Manual for Unit Sizes 6x
6
87