GE Industrial Solutions AF-600 FP High Power (460V_575V 150HP and above) User Manual
Page 89
The lack of any one of these power supplies indicates the low voltage supplies on the power card are defective. This assumes of course that the proper DC bus
voltage was read at power card connector MK105 (A) and (B). Replace the power card in accordance with the disassembly procedures in Section 7 or 8.
6.3.5 Zero DC Bus Voltage Test
If no voltage is present at power card connector MK105 (A) and (B), check the condition of the DC power supply fuse. The fuse is located on the power card mounting
plate next to the power card. It can be tested without disassembling the unit.
1.
Remove power to the frequency converter and make sure the DC bus is fully discharged by measuring the voltage at the power card connector MK105
(A) with respect to MK105 (B).
If the DC power supply fuse is open (blown), it is not possible to detect the presence of bus voltage at these terminals. If uncertain, wait 20
minutes for 4x-frame sizes or 40 minutes for 5x-frame sizes to allow the DC bus to fully discharge. See label on front of frequency converter
door for specific discharge time.
.
2. With the ohmmeter set on a diode scale or Rx100, measure from power card connector MK105 (A) to any bus bars coming from the DC inductor. Bus
bars are visible at the lower edge and beneath the power card mounting bracket. Depending on the bus bar readout, look for a diode drop or a complete
short. In either case, this indicates a fuse is in the circuit providing a path for continuity. An open reading indicates an open fuse.
If the fuse is open, it indicates a failure of the power supplies on the power card. The power card and fuse require replacement. If the fuse checks good, there may
be a problem with the soft charge circuitry. Proceed to the static checks of the soft charge and rectifier circuits earlier in this section.
6.3.6 DC Undervoltage Test
The initial charge of the DC bus is accomplished by the soft charge circuit. If the DC bus voltage is below normal it would indicate that either the mains voltage is
out of tolerance or the soft charge circuit is restricting the DC bus from charging. Conduct the input voltage test (6.3.2) to ensure the mains voltage is correct.
If excessive input power cycling has occurred, the PTC resistors on the soft charge card may be restricting the bus from charging. If this is the case, expect to read
a DC bus voltage in the area of 50 VDC.
1.
Check DC bus voltage by reading power card connector MK105 (A) with respect to MK105 (B). If verified, disconnect the power from the frequency
converter and allow it to cool for approximately 20 minutes.
2.
Reapply power to the frequency converter after 20 minutes and recheck the DC bus voltage. If voltage remains, a short circuit may exist within the
intermediate circuit preventing it from charging. Proceed to static checks (6.2) earlier in this section.
6.3.7 Input Imbalance of Supply Voltage Test
Theoretically, the current drawn on all three input phases should be equal. Some imbalance may be seen, however, due to variations in the phase to phase input
voltage and, to some degree, single phase loads within the frequency converter itself.
A current measurement of each phase will reveal the balanced condition of the line. To obtain an accurate reading, it will be necessary for the frequency converter
to run at its rated load or or at a load of not less than 40%.
1.
Perform the input voltage test prior to checking the current, in accordance with procedure. Voltage imbalances will automatically result in a corresponding
current imbalance.
2.
Apply power to the frequency converter and place it in run.
3.
Using a clamp-on amp meter (analog preferred), read the current on each of three input lines at L1(R), L2(S), and L3(T).
Typically, the current should not vary from phase to phase by more than 5%. Should a greater current variation exist, it would indicate a possible problem
with the mains supply to the frequency converter or a problem within the frequency converter itself.
AF-650 GP and AF-600 FP High Power Service Manual
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