Table of Contents
Advertisement
D-4
Meggering
7000A-UM151E-EN-P - October 2018
Potential Transformer Fuses
A Megger 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 remove a path from the power
circuit back to the drive control.
Transient Suppression Network
A path to ground exists through the TSN network as it has a
ground connection to dissipate high energy surges in normal
operation. If this ground connection is not isolated the
Megger 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 Megger test.
4. Meggering the Drive
Note: Verify the drive and any connected equipment is clear
of personnel and tools prior to commencing the Megger test.
Barricade off any open or exposed conductors. Conduct a
walk-around inspection before commencing the test.
All three phases on the line and machine sides of the drive
are connected together 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.
Note: Be sure the Megger is discharged prior to
disconnecting it from the equipment.
Connect the Megger to the drive following the specific
instructions for that model. 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. Perform a
Megger test at 5 kV for 1 minute and record the result.
7000 "A" Frame
Advertisement
Table of Contents
