Rockwell Automation 7000 PowerFlex Medium Voltage Air-Cooled (B Frame) Installation - ForGe Control User Manual
Page 83
Rockwell Automation Publication 7000-IN007E-EN-P - June 2014
83
Meggering
Appendix B
The motor filter capacitors and line filter capacitors (if applicable) may
result in the Megger test result being lower than expected. These capacitors
have internal discharge resistors designed to discharge the capacitors to
ground. If you are uncertain of the Megger test results, disconnect the
output capacitors.
5.
Reconnect connections between power circuit and low voltage control.
Reconnect the ribbon cables “J1”, “J2” and “J3” in all the VSBs. Do not
cross the cable connections. Mixing the feedback cables may result in
serious damage to the drive.
6.
Reconnect the power circuit to the system ground.
Voltage Sensing Boards
a. Securely reconnect the two ground conductors on the VSBs.
The two ground connections on the VSB provide a reference point for
the VSB and enable the low voltage signal to be fed to the SCBs. If you
do not connect the ground conductor, the monitored low voltage signal
could then rise up to medium voltage potential, which is a serious
hazard to avoid at all times. Always ensure the ground conductors on
the VSB are securely connected before applying medium voltage to the
drive.
Failure to connect both ground connections on the voltage sensing
board will result in high potential in the low voltage cabinet within the
drive that will damage the drive control, and possible cause injury or
death to personnel.
Output Grounding Network
b. Reconnect the ground connection on the OGN capacitor. The bolt
connection should torque down to 3.4 N•m (30 lb•in.). Exceeding the
torque rating of this connection may result in damage to the capacitor.
Failure to reconnect the OGN ground may result in impressing the
neutral voltage offset on the motor cables and stator, which may result
in equipment damage. For drives that did not originally have the OGN
connected (or even installed), this is not a concern.
Transient Suppression Network
c. Re-install the fuses on the TSN.
IMPORTANT
Humidity and dirty standoff insulators can cause leakage to ground because of
tracking. You may have to clean a 'dirty' drive prior to commencing the Megger
test.