Rockwell Automation 7000A PowerFlex Medium Voltage AC Drive - Air-Cooled (A Frame) - Manual (Page 252)

5-10
Component Definition and Maintenance
7000A-RM001A-EN-P – January 2011 7000 “A” Frame
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.
There are three Y-connected surge arresters attached to the incoming MV
lines. The neutral point of the arresters is connected to the ground bus.
U
Heavy duty
distribution
class surge
arrester
W V
Drive input power from
line terminals
Figure 5.9 – Surge Arresters