Synchronization is essential for running generators on a parallel bus with other generators or the utility. The generator must be synchronized to the bus voltage reference before the paralleling switchgear will close it onto the bus. This is accomplished using a synchronizer unit, which drives the generator’s governor to control its engine speed and output voltage frequency. A generator synchronizer is also used with all closed transition transfer switches. The synchronizer will sync the generator when a utility reference is presented to the line side of the transfer switch. This accommodates the closed transition from generator to utility.