Transformer-energizing inrush current: Difference between revisions

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At the moment of energizing a transformer, high values of transient current (which includes a significant DC component) occur, and must be taken into account when considering protection schemes (see {{FigRef|N32}}).
At the moment of energizing a transformer, high values of transient current (which includes a significant DC component) occur, and must be taken into account when considering protection schemes (see {{FigRef|N33}}).


{{FigImage|DB422663_EN|svg|N32|Transformer-energizing inrush current}}
{{FigImage|DB422663_EN|svg|N33|Transformer-energizing inrush current}}


The magnitude of the current peak depends on:  
The magnitude of the current peak depends on:  

Revision as of 07:03, 9 July 2018


At the moment of energizing a transformer, high values of transient current (which includes a significant DC component) occur, and must be taken into account when considering protection schemes (see Fig. N33).

Fig. N33 – Transformer-energizing inrush current

The magnitude of the current peak depends on:

  • The value of voltage at the instant of energization
  • The magnitude and polarity of the residual flux existing in the core of the transformer
  • Characteristics of the load connected to the transformer

The first current peak can reach a value equal to 10 to 15 times the full-load r.m.s. current, but for small transformers (< 50 kVA) may reach values of 20 to 25 times the nominal full-load current. This transient current decreases rapidly, with a time constant θ of the order of several ms to severals tens of ms.

ru:Ток намагничивания трансформатора при включении zh:变压器励磁涌流

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