More than the secondary winding of the power transformer whether the series and parallel ? Why series and parallel ? How to series and parallel ?
Series no big problem, the maximum current to the smallest of the group that decided to the parallel risk large point to two winding voltage is exactly equal to the job, or had large mains transformers losses. Series parallel into to pay attention to the phase series (that is, the relationship between the head and tail of the winding) inclusive of associated parallel is the head, the tail end associated. Do not pick the wrong series the wrong output voltage is the voltage difference between the two windings, and join the wrong shorted.