Why neutral is not grounded in ACS 800 12 pulse drive
Please help me in letting to know that why neutral of star winding is not grounded in 12 pulse ACS800 multi drive system.
It is clearly indicated in the manual:
"The secondaries of the transformer must not be grounded"
In order to use 12-pulse operation, you need 2 secondary windings - delta and star, each connected to own rectifier bridge in DSU module - look the diagram on page 84. So in this case, no way to ground your star secondary winding.
Of course, you can use the transformer with only one secondary winding, but you will have 6-pulse operation mode in that case.
Another note in the manual explains that you have to disconnect EMC filter option +E202, if installed, for use in IT networks (ungrounded).
Source: ACS800-07 Hardware manual