The advantage of the rotary converter over the discrete motor-generator set is that the rotary converter avoids converting all of the power flow into mechanical energy and then back into electrical energy; some of the electrical energy instead flows directly from input to output, allowing the rotary converter to be much smaller and lighter than a motor-generator set of an equivalent power-handling capability. The advantages of a motor-generator set include adjustable voltage regulation which can compensate for voltage drop in the supply network; it also provided complete power isolation, harmonics isolation, greater surge and transient protection, and sag (brownout) protection through increased momentum.