Transformer Saturation

A common misconception regarding transformers is that overloading a transformer will cause it to saturate. More technically, this implies increasing the load level increases the flux density within the core. This isn't true, under a more nuanced lens the opposite actually occurs; increasing the load level of a transformer decreases the flux density within the core.

Lets construct a transformer equivalent circuit from real-world values from the Practical Transformer Characterization Article:

Core-Loss Resistance

Magnetizing Impedance

Combined Winding Resistance

Combined Leakage Reactance

We can now subject the transformer to three levels of loading:

50W Load

100w Load

300W Load

Since the induced voltage in any coil is proportional to the flux density we can then say:

50w load

100w load

300w load

Clearly, the loading of a transformer and the operating / peak core flux density exhibit an inverse relationship, which is the opposite of what many expect.

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