Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive (A Frame) - ForGe Control - Manual (Page 63)

Rockwell Automation Publication 7000A-UM200C-EN-P - June 2014 63
Component Definition and Maintenance Chapter 3
Operation
The operation of arresters without a gap is the same as that of MOVs. Depending
on design, the arrester may also be gapped. Both gapped and un-gapped arresters
provide adequate overvoltage protection.
The arresters are able to withstand or ride through most commonly seen bus
transients within their capability. However, caution should be taken if there is a
harmonic filter on the MV bus to which PowerFlex 7000 is connected. The filter
should satisfy relevant international or local standards, such as IEEE Std 1531—
Clause 6.4, to avoid high inrush currents.
The surge arrester is certified as per ANSI/IEEE Std C62.11-1993. Certification
tests include high current short duration tests, low current long duration tests and
fault current withstand tests. The fault current withstand tests consist of different
combinations of kA and number of cycles, including a 20 kA 10-cycle test, under
which the arresters are non-fragmenting and without expelling any internal
components.
When the incoming energy exceeds the handling capability of the arrester and
causes arrester failure, the housing is designed to split open to vent without
causing damage to any adjacent components.
Surge Arrester Replacement
1. Ensure there is no power to the equipment. Isolate the drive by
lock out/tag out.
2. Wait for a minimum of 10 minutes to allow the stored energy in the drive
to be discharged.
3. Observe the location of the connecting leads.
4. Using proper method to ensure the leads are at ground potential. Use
temporary ground when necessary.
5. Detach the connecting leads.
6. Loosen the bolt that attaches the surge arrester to the ground bus. Remove
the arrester. Remove temporary ground when applicable.
7. Replace the surge arrester with an equivalent one (make sure that the
voltage rating is the same).
8. Connect the leads to the surge arrester.
9. Surge arrester hardware to be torqued to 28 N•m (21 lb•ft).
ATTENTION: To prevent electrical shock, ensure the main power has been
disconnected before working on the surge arrester. Verify that all circuits are
voltage free using a hot stick or appropriate voltage-measuring device. Failure
to do so may result in injury or death.