GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 75)

Main rectifier circuit test part I
1. Connect the positive (+) meter lead to the positive (+) DC bus connector MK105 (A) on the power card.
2. Connect the negative (–) meter lead to terminals L1, L2, and L3 in sequence.
Each reading should show infinity. The meter will start at a low value and slowly climb towards infinity due to capacitance within the frequency converter being
charged by the meter.
Incorrect reading
With the Part I test connection, the SCRs in the SCR/diode modules are reverse biased so they are blocking current flow. If a short circuit exists, it would be possible
that either the SCRs or the diodes in the soft charge rectifier are shorted. To isolate between SCRs or the soft charge rectifier, perform the Soft Charge Rectifier
Test.
Main rectifier circuit test part II
1. Reverse meter leads by connecting the negative (–) meter lead to the positive (+) DC bus connector MK105 (A) on the power card.
2. Connect the positive (+) meter lead to L1, L2, and L3 in sequence. Each reading should show a diode drop.
Incorrect reading
With the Part II test connection, even though the SCRs in the SCR/diode modules are forward biased by the meter, current will not flow through the SCRs without
providing a signal to their gates. The upper diodes in the soft charge rectifier are forward biased so the meter reads the voltage drop across those diodes.
If an open reading were present, it would indicate the upper diodes in the soft charge rectifier are open. It could also indicate that one or more of the soft charge
fuses are open. It could further indicate that the soft charge resistor is open. To isolate between the three possibilities, perform the Soft Charge Fuse Test and Soft
Charge Rectifier Test.
A short circuit reading indicates either one or more of the upper soft charge rectifier diodes are shorted or the SCRs are shorted in the SCR/diode module. To
isolate between SCRs or the soft charge rectifier, perform the Soft Charge Rectifier Test.
Main rectifier circuit test part III
1. Connect the positive (+) meter lead to the negative (-) DC bus connector MK105 (B) on the power card.
2. Connect the negative (–) meter lead to terminals L1, L2 and L3 in sequence. Each reading should show a diode drop.
Incorrect reading With the Part III test connection, the diodes in the SCR/diode modules are forward biased as well as the lower diodes in the soft charge rectifier.
The meter reads the diode drops. If a short circuit exists, it would be possible that either the diodes in the SCR/diode modules or the lower diodes in the soft charge
rectifier are shorted. To isolate between SCRs or the soft charge rectifier, perform the Soft Charge Rectifier Test.
Although an open reading is possible, it is unlikely since that indicates that both the diodes in the SCR/diode modules and the lower diodes in the soft charge
rectifier are open. Should that occur, replace both diodes.
Main rectifier circuit test part IV
1. Reverse meter leads by connecting the negative (–) meter lead to the negative (-) DC bus connector MK105 (B) on the power card.
2. Connect the positive (+) meter lead to L1, L2 and L3 in sequence. Each reading should show infinity.
Each reading should show infinity. The meter will start at a low value and slowly climb toward infinity due to capacitance within the frequency converter being
charged by the meter.
Incorrect reading
With the Part IV test connection, the diodes in the SCR/diode modules are reversed biased as well as the lower diodes in the soft charge rectifier. If a short circuit
exists, it would be possible that either the diodes in the SCR/diode modules or the lower diodes in the soft charge rectifier are shorted. To isolate between SCRs
or the soft charge rectifier, perform the Soft Charge Rectifier Test, 6.2.2.
6.2.2 Soft Charge Rectifier Test: 4x-frame size
Testing the soft charge rectifier requires access to the soft charge card connectors. It requires removing the control card and power card mounting plate. Refer
to removal instructions for soft charge card in Section 7.
Do not remove the soft charge card completely or unplug any connectors not called out. Doing so will break the continuity path of these measurements and may
result in a false interpretation of a failure. Although an open reading is possible, it is unlikely since that indicates that both the diodes in the SCR/diode modules
and the lower diodes in the soft charge rectifier are open. Should that occur, replace both diodes.
1. Extract the soft charge card far enough to access the connectors.
AF-650 GP and AF-600 FP High Power Service Manual
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