Parallel/series inductors for Boost converter ???

[moshik3]

Hi,

For a PFC boost converter, I need a 470uH at about 4A Isat., maybe a bit more.
these are quite hard to find.

can I use 4 pieces of 470uH 2A inductors in series parallel ?
2 in series will give 940uH, and then paralleled to another series couple, it will give 470uH again.

What about the current ? will it divide among the 4 components ? will I have actually 4x 2A = 8A Isat ?

Are there any other cons for doing this (assuming this comes cheaper than using one "correct" inductor) ?
any magnetic interference or other problem ?
Thanks !

 

[moshik3]

maybe...someone... ?

 

[mtwieg]

If the current divides evenly then you'll get twice the current rating, but the division is never perfect, so it's hard to say. One possible problem with series inductors is the midpoint ringing a lot due to the self resonance of the inductors. If this is a problem then damping it with a RC snubber network may be necessary.

 

[goldsmith]

For a PFC boost converter, I need a 470uH at about 4A Isat., maybe a bit more.
these are quite hard to find.

Hi moshik3

Is that hard to find ? so why you don't twist it yourself ? it can be a better idea rather than use some of them in series and in parallel . isn't it ?

can I use 4 pieces of 470uH 2A inductors in series parallel ?
2 in series will give 940uH, and then paralleled to another series couple, it will give 470uH again.

Of course you can . but it can be cause of more magnetic loss . but there is no special problem with that .

Best Wishes
Goldsmith

 

[moshik3]

Thanks.

Is there any calculator you would recommend for ferrite core winding ?
I searched for very long, but none of the calculators are complex,
These who calculate number of turns and core size - ignore wire gauge and saturation current.
So i don't know which core i should be using.

If i buy a 470uH at 2A - can i REWIND it to be 1000uH at 2A with the same core ?
in other words, is it the core size that sets the saturation current ?

and If i need more current, do i have to find a bigger core ?
or bigger gauge wire on the same core will do ?

 

[FvM]

There are "complex" calculators, e.g. the ferrite tool downloadable from Epcos.

Saturation of a particular core (material, cross section, effective magnetic length, air gap) is given as a specific ampere-turns product. So rewinding an inductor will of course change the saturation current. As you might guess, increasing the inductance gives a lower saturation current.

 

[BradtheRad]

You can combine 2 or more boost converters in parallel (interleaved).

Each would contain a 470 uH coil with a 2A saturation spec.

To illustrate a quadruple converter:

 

[goldsmith]

Is there any calculator you would recommend for ferrite core winding ?

Hi again
Take a look through here :
https://www.edaboard.com/threads/229615/

whole thread is dealing with how to calculate inductors and how to wind them and how to select a core . read all of the pages of that .
Best Wishes
Goldsmith