# How does Impedance affect Transformer Size?

**URL:** <https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980>\
**Category:** Electrical\
**Tags:** transformer, electrical\
**Created:** [April 20, 2024, 3:35am UTC](https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980 "2024-04-20T03:35:32Z")\
**Posts on this page:** 4\
**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:** [April 20, 2024, 3:35am UTC](https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980/1 "2024-04-20T03:35:33Z")

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How Does Impedance Affect Transformer Size?

 ![IMG_20240420_090405](https://cdn.forumautomation.com/original/2X/a/a23b918fbe54aaff8fda0d6614fb0d076f1b2aa4.jpeg)

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<div class="post-metadata">

**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [April 20, 2024, 7:48am UTC](https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980/2 "2024-04-20T07:48:06Z")

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Impedance influences transformer size primarily because it impacts the amount of current required to generate a particular quantity of power.

A lower impedance transformer will need thicker wire and a larger core material to withstand higher currents, results in a larger physical dimension.

In contrast, a higher impedance transformer may constitute smaller as it requires less current handling capacity.

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<div class="post-metadata">

**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [July 17, 2026, 2:37pm UTC](https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980/3 "2026-07-17T14:37:20Z")

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## What is the 80% rule for transformers?

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<div class="post-metadata">

**Author:** ![TSRS](https://forumautomation.com/user_avatar/forumautomation.com/tsrs/32/8023_2.png) [@TSRS](https://forumautomation.com/u/TSRS)\
**Post date:** [July 17, 2026, 2:42pm UTC](https://forumautomation.com/t/how-does-impedance-affect-transformer-size/11980/4 "2026-07-17T14:42:04Z")

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The 80% rule for **[electrical transformers](https://forumelectrical.com/electrical-transformers-formulas-and-equations/)** is a protection recommendation that states that a transformer’s continuous load should not exceed 80% of its rated **[kVA (kilovolt-ampere)](https://forumelectrical.com/kw-to-kva-calculator/)** capacity.

This guideline creates a safety buffer to avoid overheating, reduce insulation deterioration and handle temporary power surges.