This term sometimes refers to a solid-state phase converter, a patented design that uses a series of variable frequency drives, also known as vfds, with capacitors to provide three-phase power. In many other cases, the term refers to a rotary phase converter that is digitally controlled.

Both devices can facilitate phase conversion, from single phase to three phase. Choosing one over the other depends on a handful of factors, such as the number of machines connected to the unit, motor power requirements and costs. All of these variables will be addressed in this section of the article.