# Transformer Short-Circuit Current and Percentage Impedance Calculation

**URL:** <https://forumautomation.com/t/transformer-short-circuit-current-and-percentage-impedance-calculation/14596>\
**Category:** Electrical\
**Tags:** electrical\
**Created:** [November 12, 2026, 1:43pm UTC](https://forumautomation.com/t/transformer-short-circuit-current-and-percentage-impedance-calculation/14596 "2026-11-12T13:43:22Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [November 12, 2026, 1:43pm UTC](https://forumautomation.com/t/transformer-short-circuit-current-and-percentage-impedance-calculation/14596/1 "2026-11-12T13:43:22Z")

</div>

## Transformer Short-Circuit Current and Percentage Impedance Calculation

Transformer full-load current is determined by its rated kVA and operating voltage. The percentage impedance (%Z) is used to estimate the prospective **[short-circuit current](https://forumelectrical.com/transformer-short-circuit-current-calculation/)** at the transformer terminals.

 ![1](https://cdn.forumautomation.com/original/2X/a/ac249b15fb3efb0d91ce15e4fb094a8f87eabd02.jpeg)

## Calculation Formulas

**Three-Phase Full-Load Current:** I\_FL = (kVA × 1,000) / (√3 × V)

**Transformer-Terminal Short-Circuit Current:** I\_SC = I\_FL × (100 / %Z)