I'm not a big fan of shunt trips, as they require power to operate. In the small, molded-case breakers, they require another pole space in the panel, which could usually be better utilized.
The field installed trip units are just a little magnet coil, with short leads, that "coerce" the C/B's magnetic trip.
Like Bob says, I haven't seen them used on elevators recently.
(What would happen if Ella Fitzgerald married Darth Vader?? She'd become Ella Vader)
Let the boos and rotten tomatoes fly.
...S
