Re: Buck-boost transformer sizing question
Not exact science but close enough.
The voltage stability of buck-boost transformer arrangements is not any more load depedent then any other arrangement. While autotransformers only transform a portion of the total circuit current, they do transform 100% of their rated current and voltage.
Standard buck-boost changes are: 5%, 10%, and 20%, for 120/240-12/24V transformers; and 6.6%, 13.3 and 26.6% for 120/240-16/32V units. The relevant formulas are; %V=(HV-LV)/LV, LV=HV/(1+%V), and HV=LV*(1+%V).
Just because you can, doesn't mean you should.