How to determine a Transformers primary current.

[fullwidth backgroundcolor=”” backgroundimage=”” backgroundrepeat=”no-repeat” backgroundposition=”left top” backgroundattachment=”scroll” video_webm=”” video_mp4=”” video_ogv=”” video_preview_image=”” overlay_color=”” overlay_opacity=”0.5″ video_mute=”yes” video_loop=”yes” fade=”no” bordersize=”0px” bordercolor=”” borderstyle=”” paddingtop=”20px” paddingbottom=”20px” paddingleft=”0px” paddingright=”0px” menu_anchor=”” equal_height_columns=”no” hundred_percent=”no” class=”” id=””][blog number_posts=”” cat_slug=”” exclude_cats=”” title=”yes” title_link=”yes” thumbnail=”yes” excerpt=”yes” excerpt_length=”35″ meta_all=”yes” meta_author=”yes” meta_categories=”yes” meta_comments=”yes” meta_date=”yes” meta_link=”yes” meta_tags=”yes” paging=”yes” scrolling=”pagination” strip_html=”yes” blog_grid_columns=”3″ blog_grid_column_spacing=”40″ layout=”large” class=”” id=””][/blog][title size=”1″ content_align=”left” style_type=”single” sep_color=”” class=”” id=””]Determining the primary current in a transformer.[/title][youtube id=”n4BrGVrZMfA” width=”600″ height=”350″ autoplay=”no” api_params=”” class=””][fusion_text]

Why do we have to over complicate things with transformers?

When it comes to transformers it is really easy to over complicate the issues (kinda the same about life too eh?).  Well it’s my job to simplify things so here we go.  This is especially true when we are talking about determining the primary current of a transformer.

There are a few ways to do it.  The hard way and the easy way.

Guess which one is which.

Do we use the turns ratio of the transformers?

Nope.  It can be done but I find it can be confusing and very easy to make mistakes.

Then what do we do?

One of the cardinal rules of transformers is this:

KVA in = KVA out

I don’t care who you are or where you are from.  This is a truth.  This makes solving primary current ridiculously easy.

If we can determine what the secondary is using for power (which should be a non issue), then we know what the primary is having to supply (hint: they are the same thing!!).

All we have to do is take that power and divide it by our primary voltage and there you go, Primary current solved.

Are you sure it’s that easy?

Yup and you’re welcome 🙂

One caveat when working out primary current calculations.

This example is neglecting any losses.

This means we are assuming that power input is equal to power output.

As efficient as transformers are they are not 100% efficicient (96-99%).  They will experience some losses in the core and the windings but that is another discussion for another time.[/fusion_text][/fullwidth]

Comments on How to determine a Transformers primary current.

  1. Faruk says:

    I read your post very helpful to me because i am a Engineer.

    1. Dan says:

      If you are ‘a Engineer’ you should know this already.

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