Specifications

RT9 Powershelf Rectifier Technologies
158-1806-01.doc
14 2-Mar-06
3.3.5 Surge protection requirements
The rectifiers are internally protected for surges up to 6kV/3kA. For higher levels of
protection, particularly for sites with high incidence of lightning or switching surges,
additional surge protection is required on the AC feed to the Powershelf. Typically surge
arrestors with a 10kA-40kA rating are required with the highest level of protection being
provided when arrestors are connected between phase-netural (x3 phases) and between
phase/neutral-earth (x 3 phases).
Other arrangements (for 3-phase “star”) with similar levels of protection are also possible
as shown below. The voltage rating of the arrestor should be selected based on the
maximum AC voltage likely to appear on the line. The arrestor should limit the voltage to
<1200V – 1400V at the rated maximum pulse current.
Figure 3.8