Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control (PanelView 550) - Manual (Page 282)

282 Rockwell Automation Publication 7000-UM151E-EN-P - January 2013
Appendix D Meggering
All three phases on the line and machine sides of the drive connect through
the DC Link and snubber network. Therefore a test from any one of the
input or output terminals to ground will provide all the sufficient testing
required for the drive.
a. Connect the Megger to the drive following the specific instructions for
that model.
b. If the Megger has a lower voltage setting (normally 500V or 1000V),
apply that voltage for 5 seconds as a precursor for the higher voltage
rating. This may limit the damage if you forgot to remove any grounds.
If the reading is very high, apply 5kV from any drive input or output
terminal to ground.
c. Perform a Megger test at 5 kV for 1 minute and record the result.
The test should produce a reading greater than the minimum values
listed below. If the test results produced a value lower than these values
start segmenting the drive system down into smaller components and
repeat the test on each segment to identify the source of the ground
fault. This implies isolating the line side of the drive from the machine
side by removing the appropriate cables on the DC Link reactor.
You may need to completely isolate the DC Link reactor from the drive, at
which point you must disconnect all four power cables. You must ensure
that you have electrically isolated all electrical components to be meggered
from ground.
Items that may produce lower than expected readings are surge capacitors
at the motor terminals, motor filter capacitors at the output of the drive.
The meggering procedure must follow a systematic segmentation of
electrical components to isolate and locate a ground fault.
ATTENTION: Discharge the Megger prior to disconnecting it from the
equipment.
Type of Drive Minimum Megger Value
Liquid Cooled Drive 200 M Ohms
Air Cooled Drive 1k M Ohm
Drive with input/output Caps Disconnected 5k M Ohm
Isolation Transformer 5k M Ohm
Motor 5k M Ohm