GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 92)

With a phase loss, the current waveform of the remaining phases would take on the appearance shown in Illustration 6-15.
Illustration 6.15: 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 and also the dynamic SCR/diode module
test.
6.3.9 Input SCR Test
The SCR can be disabled by the frequency converter for various reasons. Check the following before making more complicated tests.
The SCRs can be disabled as a result of an input, or lack of input, at power card connector FK102, the external brake temperature switch. Unless used as an input,
a jumper must be placed between terminals 104 and 106 of FK102
The SCRs are gated in sequence with the main supply. Verify that the voltage reference signal is correct as follows.
1. Using a voltmeter, measure phase to phase mains voltage at Terminals R, S, and T of power card connector MK106.
2. Measurements should correspond with measurements called out in the Input Voltage Test (6.3.2).
An incorrect reading at MK106 with a correct input voltage may indicate a problem in the soft charge card or the connecting cable.
If the above tests reveal no abnormalities, it is further possible that the inrush signal has not been enabled by the control card. Using the signal test card, verify
the inrush signal is present and the SCR disable signal is at the correct voltage level as follows.
3. Insert the signal test board into power card connector MK104.
4. Check the SCR disable signal.
5. Using a voltmeter, connect the negative (-) meter lead to terminal 4 (common) of the test board.
6. Connect the positive (+) meter lead to terminal 19 of the signal board.
A reading of 0 VDC indicates the SCRs have been disabled. A reading of 0.6 to 0.8 VDC indicates the SCRs are active and should be gated.
With a reading of 0 VDC and proper mains applied to the frequency converter, it would be likely that the input at power card terminal FK102 has caused the SCRs
to be disabled. Given the connection at FK102 has been verified the control card would be suspect. Check the inrush signal as follows.
7. Connect the positive (+) meter lead to terminal 7 of the signal board.
A reading of 0 VDC indicates the inrush signal is active and the SCRs are being gated. A reading of 5 VDC indicates the inrush signal is inactive and the SCRs are
not gated.
With a reading of 5 VDC and proper mains applied to the frequency converter, it would be likely that the control card is defective.
AF-650 GP and AF-600 FP High Power Service Manual
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