Buck-Boost Transformer. The advantages of using a buck-boost transformer over an equivalent standard isolation transformer are: Used in a variety of applications 2. Inexpensive and stocked voltage correction 3. Smaller and lighter than an isolation transformer. Buck-boost transformers offer an economical solution to the adjustment of line voltages that are slightly above or below normal. When a buck-boost transformer is connected as an autotransformer, only a portion of the load kVA is actually transformed. The majority of the load kVA is passed directly through to the source. For this reason a buck-boost transformer may be used to supply a much larger kVA load than is indicated on the nameplate. Buck-boost transformers represent an economical way to both raise supply voltage caused by line drop or equipment demand on the distribution system, or lower voltage caused by increased system voltages due to supply line adjustments. Some loads including lighting and resistive loads require a stable supply to maintain performance. The detrimental effects of incorrect supply line voltage can cause equipment failure. Buck-boost transformers can correct line voltage within 5 to 25% of nominal.