Type AC RCCB is designed to trip with sinusoidal residual currents which occur suddenly or slowly rise in magnitude. Type AC RCCB is only designed for use with linear loads that produce sinusoidal residual currents at 50Hz.
Type A: Certain devices during faults can be the source of non-sinusoidal earth leakage currents (DC components) due to the electronic components e.g.: diodes, thyristors. The type A RCCB is designed to ensure that under this conditions the RCCB operates on sinusoidal residual current and also with pulsating direct current which occur suddenly or slowly rise in magnitude.