对于所有实际目的来说，直流发电机仅用于特殊场合和地方性发电厂。这个局限性是由于换向器要把发电机内部的电压整流为直流电压，因此使大规模直流发电不能实行。
结果，所有大规模生产的电能都以三相交流电的形式生产和分配。今天固态转换器的应用使交流变直流成为可能。而且，直流发电机的操作特性一直重要，因为大部分的理论能被应用到所有其它机器上。
For all practical purposes, the direct-current
generator is only used for special applications
and local dc power generation. This limitation
is due to the commutator required to rectify the
internal generated ac voltage, thereby making
largescale dc power generators not feasible.

Consequently, all electrical energy produced
commercially is generated and distributed in the
form of three-phase ac power. The use of solid
state converters nowadays makes conversion to dc
economical. However, the operating
characteristics of dc generators are still
important, because most concepts can be applied
to all other machines.