Rockwell Automation 7000L PowerFlex 7000 Medium Voltage AC Drive C Frame - Marine - Manual (Page 185)

Component Definition and Maintenance 4-9
7000 ―C‖ Frame - Marine 7000L-UM302B-EN-P – June 2013
Metal-oxide varistors (MOV) are part of the Transient Suppression
Network located within the connection cabinet.
1. Ensure there is no power to the equipment.
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 transient suppression network. 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. 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.
I M P O R T A N T I M P O R T A N T Each MOV panel is grounded. Ensure that one
MOV (see Figure 4.8 for location) is connected to
the grounding lead.
Surge Arresters Description
Heavy duty distribution class surge arresters are used 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 basically MOVs, with or without an air gap in
series, packed in sealed housing. They provide overvoltage protection
similar to what the TSN module does. They differ from the TSN in
that fusing is not required for the operation of surge arresters.
There are 3 types of surge arresters depending on the voltage class of
the drive as shown in the table below:
Drive voltage 2.4 kV 3.3 kV 4.16kV, 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
The most severe temporary overvoltage occurs when one phase is
grounded in an ungrounded system. The full line-to-line voltage is
applied to the arrester in this case. The arresters are designed to operate
under this condition continuously without any problems as shown by
their Maximum Continuous Operating Voltage (MCOV) rating.
Metal-Oxide Varistor
Replacement