To achieve the buck/Improve feature, all that is required is 2 different switches so the AC enter is often linked to one of the two Most important taps, though the load is linked to another, So utilizing the key transformer's Key windings as an autotransformer. Case in point #seven - https://damienddzwt.gynoblog.com/32992876/the-smart-trick-of-ups-uninterruptible-power-supply-that-no-one-is-discussing