GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 91)

6.3.8 Input Waveform Test
Testing the current waveform on the input of the frequency converter can assist in troubleshooting mains phase loss conditions or suspected problems with the
SCR/diode modules. Phase loss caused by the mains supply can be easily detected. In addition, the rectifier section is controlled by SCR/diode modules. Should
one of the SCR/diode modules become defective or the gate signal to the SCR lost, the frequency converter will respond the same as loss of one of the phases.
The following measurements require an oscilloscope with voltage and current probes.
Under normal operating conditions, the waveform of a single phase of input AC voltage to the frequency converter appears as in Illustration 6-13.
Illustration 6.13: Normal AC Input Voltage Waveform
The waveform shown in Illustration 6-14 represents the input current waveform for the same phase as Illustration 6-13 while the frequency converter is running
at 40% load. The two positive and two negative jumps are typical of any 6 diode bridge. It is the same for frequency converters with SCR/diode modules.
Illustration 6.14: AC Input Current Waveform with Diode Bridge
AF-650 GP and AF-600 FP High Power Service Manual
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