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7000 "A" Frame
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.
The DC Link reactor may have to be completely isolated
from the drive, at which point all four of its power cables
must disconnected. It is imperative to ensure the electrical
components to be meggered are electrically isolated 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.
Type of Drive
Liquid Cooled Drive
Air Cooled Drive
Drive with input/output
Caps Disconnected
Isolation Transformer
Motor
Note: 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.
Note: Humidity and dirty standoff insulators may also cause
leakage to ground because of tracking. You may have to
clean a 'dirty' drive prior to commencing the Megger test.
5. Reconnecting 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.
Meggering
Minimum Megger Value
200 M Ohms
1k M Ohm
5k M Ohm
5k M Ohm
5k M Ohm
7000A-UM151E-EN-P - October 2018
D-5
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