I have an inverter circuit in which I want to filter the output with an LC filter. Lets say the fundamental component that I want is 60Hz.
When designing a Low Pass LC filter, I need to use the load impedance. In this case it is 100 Ohms and it is placed on the high side of a transformer. The LC filter will be on the low side of the transformer.
Do I use the impedance value from the high side in my LC Low pass calculations or do I have to use the equivalent impedance that would be seen on the low side for the LC low pass calculations?
Shown below is an example circuit.
Best Answer
You use the reflected version from high to low. You turns ratio is 10:1 so the 100 ohms on the secondary will appear as 1 ohm on the primary.
But, you mention low pass filtering the 60 Hz - stay as far from the 60 Hz as you can because although the Ls and Cs you have drawn make a low pass filter, at resonance they are series resonant and will act as almost a dead short. The resonant frequency is: -
\$\dfrac{1}{2\pi\sqrt{LC}}\$ Hz where L = L1 + L2 and C = C1 + C2
Just be aware of this in order to avoid burning stuff!!!