Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) User Manual
Page 253
Component Definition and Maintenance 5-11
7000 “A” Frame
7000A-RM001A-EN-P – January 2011
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 PF7000 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 20kA 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.
A T T E N T I O N
A T T E N T I O N
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.
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 Nm (21ft/lbs).