Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control - Manual (Page 39)

Rockwell Automation Publication 7000-UM202B-EN-P - June 2014 39
Component Definition and Maintenance Chapter 3
Replacing Metal-Oxide Varistors
Metal-oxide varistors (MOV) are part of the TSN located within the connection
cabinet.
1. Ensure there is no power to the equipment.
2. Observe the locations of the connecting links.
3. Detach the connecting links by removing the screws.
4. Using a screwdriver remove the screws at the base.
5. Replace the MOV (polarity is not an issue).
6. Continue by replacing the screws and connecting links.
Each MOV panel is grounded. Ensure that one MOV (see Figure 28 on page 38
for location) connects to the grounding lead.
Surge Arresters
These medium voltage drives use heavy duty distribution class surge arresters for
transient overvoltage protection in the drives with AFE rectifiers. The arresters
are certified as per ANSI/IEEE Std C62.11-1993.
The surge arresters are MOVs, with or without an air gap in series, in sealed
housing. They provide overvoltage protection similar to that of the TSN module.
They differ from the TSN in that fusing is not mandatory for the operation of
surge arresters.
There are three types of surge arresters depending on the voltage class of the
drive:
The most severe temporary overvoltage occurs when one phase is grounded in an
ungrounded system. The full line-to-line voltage applies to the arrester in this
case. The arresters operate under this condition continuously without any
problems as indicated by their Maximum Continuous Operating Voltage
(MCOV) rating.
ATTENTION: To prevent electrical shock, disconnect the main power before
working on the drive. 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.
Drive Voltage 2.4 kV 3.3 kV, 4.16 kV, 4.8 kV 6.0...6.9 kV
Arrester rating (RMS) 3 kV 6 kV 9 kV
Arrester MCOV (RMS) 2.55 5.10 7.65