Tower rectifiers

In electrical engineering practice the problem of converting alternating current to direct current is frequently encountered. In the present stage of the art alternating current has to be employed for the transmission of energy if the distance or the amount of energy exceeds certain comparatively low limits. On the other hand, in many applications of electricity direct current has definite advantages over alternating current; for example, in tramway operation, in hoisting, in driving variable-speed machine tools, etc., and it is usually a combination of transmission and application problems which brings the engineer face to face with the question of conversion.