It combines a D-characteristic MCB for motor or high-inrush loads with a Type A residual-current device tripping at 100 mA. That Type A rating means it detects pulsating DC fault currents — the kind a single-phase rectifier or VFD front end can produce — not just pure sinusoidal AC leakage.
The D characteristic provides a higher magnetic trip threshold (10 to 20 times In), sized for loads with a starting surge — transformers, small motors, solenoid banks. The 100 mA residual sensitivity is a deliberate choice: it's above the 30 mA threshold for personal shock protection, typically specified for equipment protection (fire prevention, insulation monitoring) or for circuits where nuisance tripping from normal leakage would be unacceptable. On a 4-pole 63 A frame, this combination suits sub-distribution feeding mixed inductive and electronic loads where earth-leakage coordination with upstream RCDs matters.