Variable speed fire pump controllers can use variable frequency drives (VFDs) to control pump speed. VFDs have several elements including rectifiers, DC links, and inverters. They provide soft starting for motors but can also affect motors and electrical systems. Proper motor requirements, testing, and system tuning are needed for fire pump applications.
17. Schematic Diagram Single Source A.T.L. (D.O.L.) Starting in Bypass Mode Low to Moderate Horsepower Note Mechanical Interlock (Mech Intk) Between R1 and BP Contactors.