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4 Harmonics generatorsIn industrial applications, the main types ofequipment that generate harmonics are:c static converters,c arc furnaces,c lighting,c saturated reactors,c other equipment, such as rotating machineswhich generate slot harmonics (often negligible).4.1 Static converters on 3-phase networksRectifier bridges and, more generally, staticconverters (made up of diodes and thyristors)generate harmonics.For instance, to deliver a perfect DC current,a Graetz bridge requires a rectangular pulsedAC current when the load is highly inductive(see fig. 5 ), or tips when the bridge is followedby a capacitor (see fig. 6 ).LoadITITttT/6 T/3Rectifier supply phase currentT/6Phase current upstream from a delta-starconnected transformer supplying the rectifierFig. 5 : alternating current upstream of a Graetz bridge rectifier delivering a perfect direct current on a highlyinductive load.i1u1u2u3i1i2i3CLoadu1Fig. 6 : alternating current upstream of a Graetz bridge rectifier followed by a capacitor.Cahier Technique Schneider Electric no. 152 / p.9