McDonalds using a 3 phase 208/120Y from a 7620/13200Y 300KVA transformer. Meter is a GE kV2C. The pad transformer's input is 3 phase 7620 volts to neutral and 13200 volts "hot" line to line of each of the 3 phases. The output is 3 phase 120 volts line to neutral and 208 volts line to line of each hot phase. This pad transformer has a turns ratio of 7620/120 =63.5 The 120 volt single phase service is for lighting, computers, signage, drink machines, cash registers etc. The 3 phase 208 volts is for the ice machines, Air Conditioners, Food Freezers, i.e. any place where the load is usually larger. Some devices also use might use single phase 208 volts say on a bathroom air heated hand dryer. The breaker box of course has 3 "hot" bus bars 120 volts to neutral i.e. say about ground. 208 volt single phase has a 2 pole breaker that grabs 2 "hot" 120 volt bus bars. The voltage is 208 volts not 240 volts because the two 120 volt phases are not in phase. A dumb AC voltmeter across the two phases measures 208 volts.

свернуть