Rockwell Automation 7763 Medium Voltage OneGear SMC Flex Motor Controller (10-15 kV) - Manual (Page 103)

Rockwell Automation Publication 7760-UM001D-EN-P - October 2014 103
Troubleshooting Chapter 8
To install control module, follow the reverse order for removal.
Note: The MV SMC Flex must use firmware release 6.003 or later. This User
Manual pertains to units with firmware released 6.003 or later.
Voltage Feedback Circuit Test The most straightforward means of checking the feedback circuits is to perform
the "
Voltage-Sensing Board Replacement on page 103 ". Another possible test
involves measuring the feedback voltages at the interface board (see Figure 27 ).
This can only be done with line voltage applied. If the motor does not start, it
may be necessary to temporarily modify the control circuit to close the line
contactor without applying a start signal to the SMC Flex module. In this case,
the three line voltages (Line A, Line B, Line C) measured with respect to ground
should be approximately 1 volt rms. It is important that the level in each phase is
the same as the other phases, within +/- 1%.
If any voltage is well outside this range, there may be a problem either with the
system voltage, or with the voltage sensing board. Note that the load side voltages
(Load A, Load B, Load C) will be very low, since the SCRs are not turned on, and
only a low leakage current flows to the motor.
If the motor will start and run, the line and load voltages should be the same
when the bypass contactor is closed.
Voltage-Sensing Board
Replacement 1. Ensure there is no power to the equipment.
2. Mark the position of the ribbon cable and wires.
3. Disconnect the high voltage wires from the end that connects to the bus
bars, and release the wires from the plastic stand off clips.
4. Release the locking mechanism located on each side of the ribbon cable
connector and pull the ribbon cable straight out to prevent bending the
pins. Remove the green ground wires.
5. Remove the four fasteners that secure the assembly to the panel. Remove
assembly including high voltage wires from the equipment.
ATTENTION: When removing the control module, make sure to hold the
module in place as the screws are removed, to avoid strain on the ribbon cables.
SHOCK HAZARD: To prevent electrical shock, ensure the main power has been
disconnected before working on the sensing board. Verify that all circuits are
voltage free using a hot stick or appropriate high voltage-measuring device.
Failure to do so may result in injury or death.