Consider a biresonant transformer with a small coupling coefficient k << 1.(adsbygoogle = window.adsbygoogle || []).push({});

Let the voltage applied to the primary LC circuit be U1(t)=U*sin(2*Pi*f*t), then also the current I1 will be sinusoidal. The voltage induced in the secondary winding and the current in the secondary LC circuit will be a positive multiple of -cos(2*Pi*f*t). Then the voltage reinduced in the primary winding will be a positive multiple of -sin(2*Pi*f*t), so it will tend to decrease the current in the primary winding. As far as I know, drawing current from the secondary winding INCREASES the current through the primary winding.

What is the explanation?

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# Resonant transformer - sign of the voltage reinduced in the primary winding

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