The information below pertains to an induction motor:

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> The magnetic capacity of the motor's magnetic (iron) circuit is designed to the relationship: voltage/frequency (V/f). If the frequency drops the V/Hz goes up. This means that the motor needs a larger magnetic circuit. Without it, the magnetic circuit can be overloaded. This is called saturation and it leads to a rapid increase in current draw and a corresponding large increase in temperature, a motor's chief enemy.
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> If the frequency increases, the V/Hz drops with no issues since the magnetic circuit will remain plenty large enough.
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<https://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/8154/Changing-an-Induction-Motors-Power-Supply-Frequency-Between-50-and-60Hz.aspx>

My question is: why does decreasing the frequency result in magnetic saturation when it doesn't cause any variations in the magnetic field of the stator?