Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - ForGe Control - Manual (Page 40)

40 Rockwell Automation Publication 7000-UM202B-EN-P - June 2014
Chapter 3 Component Definition and Maintenance
Three Y-connected surge arresters attach to the incoming MV lines. The neutral
point of the arresters connects to the ground bus.
Figure 29 - Surge arresters on incoming MV lines
Operation
Arrester operation without a gap is the same as that of MOVs in the TSN.
Depending on design, the arrester may also have a gap. Both gapped and un-
gapped arresters provide adequate overvoltage protection.
The arresters can withstand most commonly-seen bus transients within their
capability. If there is a harmonic filter on the MV bus connected to the drive, the
filter must 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 without expelling any
internal components.
When the incoming energy exceeds the handling capability of the arrester and
causes arrester failure, the housing splits open to vent without causing damage to
any adjacent components.
U W V
Drive Input from Line Terminals
Heavy-duty
Distribution Class
Surge Arrestor