Filtering an LED light's power supply

[dlgoff]

... these old power plant lessons were painful to learn but are fun to look back on.

And fun for us readers too. Keep 'em coming.

 

[jim hardy]

Thanks, Don

old jim

 

[tim9000]

so e = L d(V/R) dt = L/R dV/dt and that's differentiation. Each harmonic gets exaggerated by its order.

Thanks for the clarification as to how the harmonics exaggerates, I think I get it: So, the secondary voltage is the derivative of the primary voltage, and because the higher order harmonics have a greater rate of change than that of the fundamental, those higher order voltage components are larger in the secondary, compared to that of the fundamental component in the secondary voltage.

I drew a parallel - your example differentiated using capacitance, my example differentiated using inductance.

This may sound (and indeed be) a stupid request, but could you please re-state what your interpretation of my expectation of harmonics and capacitance was, in relation to the parallel example you outlined. Partly because I want to make sure we're both on the same page.

Thanks Jim

 

[jim hardy]

could you please re-state what your interpretation of my expectation of harmonics and capacitance was .

?? Expectations ?

Closest words to that i can remember is :

That's exactly what i hypothesized to explain your observed current wave.
What experiment could you propose to test that hypothesis?
What did you conclude from the waveform ?

I had told you what your traces looked like to me

and was soliciting your thoughts - what'd it look to you like was going on and what conclusions did you draw from your traces.

 

[jim hardy]

So, the secondary voltage is the derivative of the primary voltage, current, and because the higher order harmonics have a greater rate of change than that of the fundamental, those higher order voltage components are larger in the secondary, compared to that of the fundamental component in the secondary voltage.

 

[tim9000]

I understand that it's the current, not the voltage. But I thought you were drawing attention to the fact that e = L/R dV/dt, because you separated the 'rate of change of voltage' out.
But as long as I took the main point about how the higher order harmonics are exaggerated, than that's the main thing.

?? Expectations ?

Plainly speaking, I was trying to be reminded of what it was that I'd previously said, which spurred on your example, which you gave as a parallel.

Thanks

 

[tim9000]

How many simple ways (if any) are there to reduce the THD on the source caused by using a full-bridge rectifier load?

If you used a low pass filter and then an isolation TX (or the other way around), how much would that help (if at all)?

Would the low pass filter really do anything beneficial?

Thank you