SMA America inverter with transfomer (left) and a transformerless inverter (right) with combiner box (middle).
Courtesy SMA America
Left: This SMA America inverter has a transformer mounted behind the circuit board. One conductor of the PV system must be grounded and fusing is only on the ungrounded conductor. Middle: A transformerless inverter combiner box, with positive and negative fusing. Right: A transformerless (TL) SMA America inverter. This inverter requires an ungrounded array, and uses the combiner to provide fusing on both the positive and negative conductors.