Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 214)

9-14 COMMISSIONING
1557-UM050F-EN-P – June 2013
Meggering the 1557 Drive
NOTE: THIS IS NOT A HI-POT PROCEDURE
NOTE: Prior to performing the megger test, the following must be completed to prevent poor megger readings
and damage to the drive control boards.
The following procedure is to be used during the commissioning the 1557. Meggering the drive allows you to
find any ground faults without damaging the drive.
1. Disconnect any incoming power sources. Medium voltage sources should be locked off and all control
power should be turned off at the circuit breaker.
2. Verify with potential indicator that power has been disconnected, also, the control power in the drive is de-
energized.
3. Disconnect the following items:

The J1, J2 and Gnd. Wires on all four Voltage Feedback Boards (VFB). Before removing the J1 and
J2 connectors, label each one with „J1‟ or „J2‟ and arrow “  ” to note the polarity, this will
mitigate the re-connection process.

The Output Ground Network from the capacitor bank.

Disconnect the ground connection on the ground fault network.
4. Remove the fuses from any potential transformers connected to the system.
5. Megger the drive with a DC voltage equivalent of its AC rating. The reading should be at least 1000 M

for
air cooled drives and 200 M

for liquid cooled drives, preferred is 10 000 M

plus for one minute.
6. Record the results:
Drive Input K meg ohms
NOTE: If isolation transformer or motor have been disconnected, megger them individually and record the
results:
Motor K meg ohms
Transformer K meg ohms
7. Discharge the system to ground before touching any equipment.
8. Reconnect everything that was disconnected in step #3. NOTE: It is important that the J1 and J2 ribbon
cables are connected to the appropriate terminals on each board. Incorrect replacement of these cables
will cause serious damage to the drive. Replace all fuses that were removed, check that the correct fuse
goes to the correct location.
If you obtain values below the recommended, contact Medium Voltage Product Support.