The choke is useful for passive mode as the power goes directly to the track. If you are sending the power through the TIU, there is already a choke isolating the transformer from the DCS signal generation circuits.
@Windy City posted:The above post begs the question: Is a PSX1-AC needed/recommended on a ZW-L?
Not really sure how good the ZW-L is at circuit protection, so I can't say. Obviously, it's unlikely to hurt anything, just don't know if it offers that much additional protection.
Truthfully, though I recognize that the PSX-AC does provide good protection, sometimes it seems we go a bit overboard with these mitigation measures. Our modular club has run for many years with the Lionel Powerhouse 180 transformers running a variety of locomotives, both DCS and TMCC/Legacy. We haven't had any rashes of dead electronics, even though in a portable environment with everything clamped together and the trackwork not 100%, we have our share of derailments and shorts.
My plan on my new layout here is to run with the PH180 transformers feeding the MTH TIU and on to the track. So far, that's worked fine.
