An evaluation of exciterless topologies for medium power wound-field synchronous generators

The wound field synchronous machine has widespread use both as a motor and a generator, due to its low cost, wide power range and its consolidated history built over decades of operation. A critical aspect of these machines is the method of excitation to the field winding. Typically, the choice is between a static excitation system using slip-rings and a rotating excitation system using a brushless exciter. An alternative is that of removing the classical exciter completely and thus feed the field winding through more advanced 'exciterless' solution. The potential to reduce component count and improve power density has resulted in increasing interest in exciterless solutions, over the last couple of decades. This paper thus gives an overview of these methods, assessing and comparing their advantages and disadvantages. A particular focus is on medium power applications, which traditionally have dominated the market of synchronous generators and associated generating sets, and where significant improvements in terms of cost minimisation, power quality, and ease of design are always required.