Re: inductor sizing

Harry Dellamano wrote:

"Jamie Morken" <jmorken@xxxxxxx> wrote in message news:vB3Aj.53407$w94.15226@xxxxxxxxxxxx
Harry Dellamano wrote:

"Jamie Morken" <jmorken@xxxxxxx> wrote in message news:utnzj.44497$w94.12805@xxxxxxxxxxxx
Hi,

For a filter inductor in an LC filter, does the inductor size (core volume) scale linearly with inductance * current rating^2, all other
variables the same, ie. core material, frequency etc.

Also I need some toroid cores for 200kHz LC filters, 250uH and 50Amps
peak current, are these going to be huge cores and what core materials
would be best to use, ferrite or powder cores?

I've downloaded the www.magneticsinc.com "Magnetics Inductor Design
Using Powder Cores" program:

http://www.magneticsinc.com/software/inductor.asp


cheers,
Jamie,
I have your LCLC filter designed with all part numbers. I will sell it to you for a bottle of tequila.
What say you?
Harry


Sounds like a deal as long as you promise not to drink it all in one night :)

Just tell me where to send and your favorite type!

cheers,
Jamie
Ok Jamie,
You sound like a nice person so here is a filter design that will meet your needs with a bottle of tequila to be sent upon the design's approval. This is the first LC section for one phase and will survive the 200KHz/440VDC stress and present a nice 60Hz sine wave to the second LC section input which you can design using high flux 60Hz material to meet you unspecified output requirements. As stated earlier the THD depends on the control loop and not the HF output filter.
For the 25uH/30Apk inductor use a Ferroxcube or similar EC-70 (3F3 material) core set and bobbin with 21 turns of #10 AWG LITZ wire wound in 3 layers of 7turns/layer. Insulate all for 3500VDC. The LITZ wire should be made up with 256/#34 AWG wires. This will require a 0.21" gap across all three legs of the core. Do not grind the center leg for a 0.42" gap because this will cause increased Rac losses. The total dissipation will be <7.0W so be aware.
For the shunt caps use 5X EPCOS 2.2uF/400VDC MetalPoly at DigiKey for $1USD/100 PN B32594C6225J008. Irms in each cap is ~=1A at 200KHz which MetalPoly types of this size can handle.

Hi Harry,

Sorry for the late reply I was out of province for the last week.

For the feedback of an LCLC filter like this, are only one of the
inductor currents and capacitor voltages required, or are both
currents and voltage required?

For the LC filter version I use this algorithm for the feedback loop:

if inductor current > current_limit, pulse off

Duty cycle = ((desired voltage - current voltage) * gain) - (Inductor current * gain2)

I am not sure if I can use this for the LCLC filter as well.

Also do you have part#'s for the high flux inductor for this LCLC filter
and the output capacitor? The output is 120VAC 60Hz at 3.6kW by the
way.

I plan on using planar inductors instead of E cores and litz wire, but
I will still send you the tequila for the design :D

cheers,
Jamie





Enjoy,
Harry



.

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