Thanks HSLD for providing the correct response. Gosh...what ever happened to the good old days with real Flight Engineers, the requirement to synch the buss and oh well.... (Please don't respond folks. I know the answer to the question !)

For AZFlyer; most electrical systems in large transport category aircraft have 3 phase AC generators. As T38 Phlyer said, it's easy and efficient to convert AC into DC power through Transformer-Rectifiers (TR) units. From the B-727 and after, Boeing used this technology and it's works well and lasts a long time.

Have a bodaceous day Mates