208V to 230V Buck-Boost Transformer — Step-up, 3-Phase Delta
See how a 208V to 230V 3-phase delta buck-boost transformer corrects voltage and how to select the proper model.
Choosing a 208V to 230V transformer
Ask why a machine built this year carries a 230V nameplate when the US nominal is 240V and there are two answers, both correct. NEMA sets motor nameplate voltages deliberately below system nominal, so a motor intended for a 240V system is marked 230V and one for a 480V system is marked 460V, leaving allowance for the drop between supply transformer and motor terminals. Separately, 230V is the harmonized supply voltage across Europe, so imported machinery arrives marked the same way. Either way the equipment expects 230V, and a 208Y/120 service does not deliver it. A 208V to 230V buck-boost transformer adds the missing 22 volts, a boost of about 10.6 percent, in single-phase and three-phase versions rated 10, 15, 20, 30, 40, 50 and 60 amps.
The 208 to 230 correction is mostly a motor problem, because motors are where the 230V nameplate convention is strongest and where missing it is measurable.General-purpose three-phase induction motors on conveyors, pumps, blowers, mixers and compressors, ordered as 230/460V dual-voltage and connected on the low tap.Imported machine tools and production equipment specified 230V single-phase or three-phase: CNC routers, packaging lines, printing and converting machinery, woodworking equipment.Refrigeration and HVAC compressors nameplated 208-230V, which sit at the very bottom of their own stated range on a real 208V service and fall below it after conductor drop.Well pumps, booster pumps and irrigation controllers built around a 230V single-phase motor.Commercial laundry, shop and laboratory equipment supplied by an OEM using a 230V electrical package.Older equipment relocated out of a building with a 240V service into a tenant space fed 208Y/120.The symptom is usually thermal or mechanical rather than electrical. The motor runs hot to the touch. The overload trips in the afternoon and resets by morning. A compressor hums and drops out instead of starting. A machine that made rate at its last address no longer does. The panel reads 208V, which looks unremarkable to anyone who has not held it next to the nameplate.