Inverters without transformers offer a higher degree of efficiency. And KACO specialises in transformerless inverters. This means: All of our single-phase units in the 00xi series operate with a full bridge without a step-up converter. According to the principle of pulse width modulation, four IGBT power switches emulate the sinusoidal voltage curve of the public power grid. This is also known as an H4 bridge and self-commutated units. However, the input voltage must be greater than the peak line voltage for it to be used.