We study the structure of power associative algebras which are train algebras. First we show the existence of idempotents, which are all principal and absolutely primitive. Then consider the train equations involving the Peirce decomposition. When the algebra is finite dimensional, it follows that the size of the Pierce components are invariant and the upper limit for its nil-indexes are studied for some idempotent. Furthermore, we show that locally train algebras are train algebras. Then we get a complete description for the set of idempotents to obtain their explicit formulas. We give attention to the case of Jordan algebras, where we discuss conditions for train power associative algebras be Jordan algebras. We also show that Jordan train algebras are finite dimensional. For Bernstein algebras of order n and period p, we prove that to have associativity in the powers we need p = 1. In this case, there are 2 n−1 possibilities of train equations, which are explicitly described.