# What is magnetizing current in a transformer?

Discussion in 'General Electronics Chat' started by logicman112, May 23, 2010.

1. ### logicman112 Thread Starter Active Member

Dec 27, 2008
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What is the magnetizing current of a transformer which its effect is considered as an inductor in the equivalent circuit of a transformer?

Hysteresis loss is the energy that is consumed to change the orientation of magnetics domains. When magnetic orientation changes, the core is magnetised and we have a total flux named Øm inside the core.( Øm is the total flux resulted from i1 and i2, the currents of primary and secondary windings).

So why the core still needs an extra current named im (magnetisation current) to be magnetised?

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2. ### t_n_k AAC Fanatic!

Mar 6, 2009
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It's not good practice to post the same question concurrently on different forums. It leads to confusion and often frustration for both you and those who try to offer advice. You'll probably find your posts will be consolidated by one of the forum moderators.

I'm referring to your very similar post on Physics ...

Last edited: May 24, 2010
3. ### t_n_k AAC Fanatic!

Mar 6, 2009
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790
The magnetising current is that current which flows in the primary winding when the primary voltage is applied with the secondary unloaded.

It's the necessary current that satisfies the excitation condition as determined by the fundamental transformer equation - as I stated in response to your other post.

This current is related (with a reasonably good approximation) to the transformer equivalent primary inductance value and the applied primary voltage and given source frequency.

Magnetising current flows into the primary irrespective of transformer load condition. The primary and secondary load components of magnetic flux are notionally in balance (by virtue of primary to secondary load ampere-turns balance) but the primary current always has a magnetising component which adds to the primary load current component. Since there is usually a phase displacement between the load and magnetising components, the effective primary current is determined by the complex number addition of the two primary components - not a simple algebraic addition.

The real transformer is a rather more complex device than suggested by the simplistic representation I have given above. A complete model of the transformer requires a detailed understanding of the various losses and their origins as well as the excitation [magnetisation] requirements.

Last edited: May 24, 2010
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