The AIF 503N-series are three-phase flicker impedances with a nominal current from 16A up to 75A per phase offering two different impedance values. Zref is used as the flicker impedance as per IEC/EN 61000-3-3 and specified by IEC 60725. Ztest is used for equipment being intended for connection to a public low-voltage distribution system having a service current supply capability of 75A and below as specified in IEC/EN 61000-3-11.