inductor sizing

Jamie Morken · 2008-03-05T02:22:18+00:00

Hi,For a filter inductor in an LC filter, does the inductor size (core volume) scale linearly with inductance * current rating^2, all othervariables the same, ie. core material, frequency etc.Also I need some toroid cores for 200kHz LC filters, 250uH and 50Ampspeak current, are these going to be huge cores and what core materialswould be best to use, ferrite or powder cores?I've downloaded the "Magnetics Inductor DesignUsing Powder Cores" program:cheers,Jamie

Mar 05, 2008 105 Replies

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tech 18 years ago

I am absolutely in awe to the welth of information found here. If I may? I am working on a similar power supply, with similar requirements as the origional poster save the 60hz final output. The supply I am working on will be directly controlling the current with little focus on the actual voltage.

The Basics, 208Vac 3phase or 220Vac single phase input rectified and filtered. I would like to use a bank of mosfets at a switching frequency around

200-250 Khz Or another possibility would be a large IGBT at around 10-12 Khz. Drive and controll considerations asside, I am looking for 2% or less of THD if possible output current will average 20-35A with a sustained 50A possible. The output voltage will be anywhere from 95V to as much as 160V DC. The full voltage of the rectified mains will be on the output untill the sustained arc is started and at which point the current regulation will be put to work. The voltage will vary and that is expected but the current must stay stable. I have a pretty good design on the controlls and feedback, But... My question is weather to use a bank of mosfets with there own LC network each, such as 5 or 6 in parallel with all outputs tied together, or1 bank of mosfets\\IGBT and a single filter?

Much Thanks Cory

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Harry Dellamano 18 years ago

Hi Cory, let me take a shot at restating your requirements. AC to DC converter. Input, 220Vac or 208V-3phase, 50 or 60 Hz with THD of the input current

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Turbo 18 years ago

Ummm... Well I had thought of that approach, however... I was looking at something considerably less complex, I hope. What I am looking at doing for the moment, I do not care about input ripple or noise. I was planning on using simple 60hz input rfi filter to a bridge rectifier, capacitors and maybe a inductor to help with ripple on the dc bus. Here is where my question starts. Similar to the original question, he had a DC supply to a mosfet bridge then an inductor out. My output needs to be very clean with

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Harry Dellamano 18 years ago

I still have a problem with your requirements, so this is a one of a kind with no AC input EMI requirements. When we state THD, we normally mean input current harmonics. The Vdc output normally has very low AC input harmonics, reduced by the loop gain, which are ignored but does have harmonics of the switching frequency (200KHz) which we call noise. So

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Turbo 18 years ago

I Apologize for my lack of proper terminology. I am trying to replace a large water cooled pass bank in a laser power supply with the pwm circuit described. The pass bank consists of 35 transistors acting like one giant variable resistor. The dc voltage in the tube can very with tube pressure and with temperature. Hence the range of voltage, however, the current must be regulated and as clean as possible.

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Harry Dellamano 18 years ago

Ah, the design is getting simpler. Let's see if I can restate the requirements. Given a 300VDC input supply, Design a Buck converter with the optimum topology to control a 20A to 50A output with 130VDC compliance. The output must have

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