ATT-GN – THREE PHASE AUTOTRASFORMERS – NEUTRAL GENERATORS from 3 to 200kVA

THREE PHASE AUTOTRASFORMERS – NEUTRAL GENERATORS from 3 to 200kVA

Different power grids in Italy and in the world do not have the Neutral; in the presence of single-phase loads or unbalanced loads it is necessary to generate a stable Neutral. When it is not necessary to separate the loads from the network with a Dyn11 isolating transformer you can use an auto-generator Neutral, incorrectly called an autotransformer as from the construction point of view it is a reactor connected to ZigZag. When you must also adapt the mains voltage (eg. From 220V to 400V) you can use a real step-up/down autotransformer with simple or double ZigZag connection.

A	B

neutral generator	step up / down neutral generator

An important application in low voltage application of the zig-zag reactors should be reported, grown in importance with the spread of non-linear loads that draw current not of sinusoidal form, containing, therefore, as to say, a high harmonic content. Such loads (rectifiers, inverters etc.) may be regarded as current generators of harmonics that cause of deforming the voltage drops on the network impedances. The phenomenon is all the more sensitive as far as the power of the distorting load is close to that of the transformer and can become absolutely intolerable when the generator is not the public network but a generator. It is therefore necessary to make sure that the impedances “found” by these currents are as small as possible. The third-harmonic currents, that is, of triple the fundamental frequency and its multiples are in a three-phase system, homopolar backhoe concerned and the impedance is that the zero sequence. The reactors in a zig-zag have, as mentioned, the zero sequence impedances that can be very low for which prevent or at least attenuate the onset of the corresponding voltage harmonics. They work so as compensating harmonics for non-linear loads. They must be installed in the immediate vicinity of the distorting load.