Where this device earns its place
Solid state overload relays in this class guard motors by sampling current through integrated CTs and tripping the contactor when the I²t curve exceeds the setpoint — they replace the bi-metallic strip on older starters where repeatability and a wider adjustment range matter. Mounting is DIN-rail under the matching contactor frame; the small footprint means a panel built around an ABB starter block will accept the 1SAZ721201R1038 without re-engineering the layout, which is usually the whole point of staying inside one vendor's family.