Rockwell Automation Publication 7000-UM202D-EN-P - May 2018 197
Insulation Resistance Test Appendix E
Grounding Network
b. Remove the ground connection on the GN (if installed). Lift this
connection at the GN capacitor rather than the grounding bus, as the
grounding cable is only rated for 600V.
3. Disconnect connections between power circuit and low voltage control.
Voltage Sensing Boards
The connections between the low voltage control and the power circuit
are made through ribbon cable connectors. The cables are plugged into
connectors on the voltage sensing board marked “J1”, “J2”, and “J3”, and
terminate on the signal conditioning boards. Every ribbon cable
connection made on the VSBs should be marked for identification from
the factory.
a. Confirm the marking matches the connections, and disconnect the
ribbon cables and move them clear of the VSB. If you do not remove
these ribbon cables from the VSB, then high potential applies directly
to the low voltage control through the ACBs, causing immediate
damage to those boards.
Potential Transformer Fuses
An insulation resistance test may exceed the rating of potential
transformer fusing. Removing the primary fuses from all potential and
control power transformers in the system will not only protect them
from damage but removes a path from the power circuit back to the
drive control.
Transient Suppression Network
A path to ground exists through the TSN network as the network has a
ground connection to dissipate high energy surges in normal operation.
If this ground connection is not isolated, the insulation resistance test
will indicate a high leakage current reading through this path, falsely
indicating a problem in the drive. To isolate this ground path, all fuses on
the TSN must be removed before proceeding with the test.
IMPORTANT Injecting a high voltage on the ground cable during an insulation resistance
test will degrade the cable insulation.
IMPORTANT The VSB ribbon cable insulation is not rated for the potential applied during
an insulation resistance test. You must disconnect the ribbon cables at the
VSB rather than the ACB to avoid exposing the ribbon cables to high
potential.
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