2 ph 440v pri & 240v 1ph sec control transformer. my ? is if pri is 2 ph how sec hav nuetral with 0v (grouded)

what is c a d g m t & numbers stand in relay name?

what is c, a, d, g and other stands in relay nomenclature?

syn motor started as induction motor. In rotor circuit emf is induced which is Ac. now when DC supply given to rotor then what happened ?