GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) - Manual (Page 76)

2. Disconnect the DC cable at the connector MK3.
Since the rectifier test requires the soft charge resistor to be in the circuit, verify the resistor is good before proceeding.
3. Measure the resistance between pins A and B of connector MK4 on the soft charge card. It should read 27 ohms ( ±10%) for 380–480V frequency
converters and 68 ohms ( ±10%) for 525–690V. A reading outside this range indicates a defective soft charge resistor. Replace the resistor in accordance
with disassembly procedures in Section 7. Continue tests.
Should the resistor be defective and a replacement not readily available, the remainder of the tests can be carried out by disconnecting the cable at connector
MK4 on the soft charge card and placing a temporary jumper across pins A and B. This provides a path for continuity for the remaining tests. Ensure any temporary
jumpers are removed at the conclusion of the tests.
For the following tests, set the meter to diode check or Rx100 scale.
4. Connect the negative (-) meter lead to the positive (+) MK3 (A) (DC output to DC bus), and connect the positive (+) meter lead to MK1 terminals R, S, and
T in sequence. Each reading should show a diode drop.
An incorrect reading here indicates the soft charge rectifier is shorted. The rectifier is not serviced as a component. Replace the entire soft charge card in accordance
with the disassembly procedures in Section 7.
5. Reverse meter leads with the positive (+) meter lead to the positive (+) MK3 (A). Connect the negative (-) lead to MK1 terminals R, S, and T in sequence.
Each reading should show open.
6. Connect the positive (+) meter lead to the negative (-) MK3 (C). Connect the negative (-) meter lead to MK1 terminals R, S, and T in sequence. Each
reading should show a diode drop.
An incorrect reading here indicates the soft charge rectifier is shorted. The rectifier is not serviced as a component. Replace the entire soft charge card in accordance
with the disassembly procedures in Section 7.
7. Reverse the meter leads with the negative (-) meter lead to the negative (-) MK3 (C). Connect the positive (+) meter lead to MK1 terminals R, S, and T in
sequence. Each reading should show open.
If all tests indicate correctly while isolating between the SCR/diode modules and the soft charge card, the SCR/diode modules are suspect. Before reconnecting
the cable at MK3, return to the Main Rectifier tests and repeat those tests. Put the power card temporarily back in place to retest the main rectifier. Replace any
defective assemblies in accordance with the disassembly procedures in Section 7.
130BX71.10
1
2
3
4
Illustration 6.7: Soft Charge Card Connectors
380–480V: Blue MOV & 8 PTCs 525–690V: Red MOV & 6 PTCs.
1 MK1 3 MK4
2 MK2 4 MK3
AF-650 GP and AF-600 FP High Power Service Manual
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