424 Rockwell Automation Publication 7000L-UM301F-EN-P - March 2020
Appendix C Meggering
The following procedure details how the Megger test on the PowerFlex 7000L is
to be performed. Failure to comply with this procedure may result in poor
Megger reading and damage to drive control boards.
Equipment Required
• Torque Wrench and 7/16 inch socket
• Phillips Screwdriver
• 2500/5000 Volt Megger
Procedure
1. Isolate and Lock Out the Drive System from High Voltage
Disconnect any incoming power sources, medium voltage sources should
be isolated and locked out and all control power sources should be turned
off at their respective circuit breaker(s).
Verify with a potential indictor that power sources have been
disconnected; also, the control power in the drive is de-energized.
2. Isolate the Power Circuit from System Ground (Float the drive)
It is necessary to remove the grounds on the following components within
the drive (Refer to the electrical diagrams provided with the equipment to
assist in determining the points which need to be disconnected):
• Voltage Sensing Boards (VSB)
• Output Grounding Network (OGN)
Voltage Sensing Boards
Remove all ground connections from all of the VSBs in the drive. This has
to be done at the screw terminals on the VSB rather than the ground bus.
There are two grounds on each board marked “GND 1”, and “GND 2”.
The number of VSBs installed in each drive varies depending on the drive
configuration.
Output Grounding Network
Remove the ground connection on the OGN (if installed). This
connection should be lifted at the OGN capacitor rather than the
grounding bus as the grounding cable is only rated for 600 V.
It is important to disconnect the terminals on the boards rather than
from the ground bus as the grounding cable is only rated for 600 V.
Injecting a high voltage on the ground cable will degrade the cable
insulation. Do not disconnect the white medium voltage wires from
the VSBs. They must be included in the test.
Injecting a high voltage on the ground cable during a Megger test will
degrade the cable insulation.
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