# Flux cancellation

Started by September 23, 2018
```In this short movie the guy explains the technology behind his 1kW LLC
converter:

https://youtu.be/wtcn6rZE1Eg

At 0:57 he replaces a monolithic 16:2x1 transformer with 4 4:2x1
transformers, which is a basic matrix transformer technology. OK.

At 1:50 he merges two U-shaped transformers into a single E core,
still fine.

At 2:04 I got lost. He removes the center leg of the E core,
basically returing to the U shape. But this is topologically
equivalent to a toroid with 2x4 primary windings, in other words
an 8:4x1 transformer. Since B=mu*H and H~N*I, he has flux doubling,
not cancellation. He correctly concludes "half core size" (precisely,
volume), but how did he get "half core losses"? Putting all the
non-linearities aside, P_loss(B, 2*volume) ~= P_loss(2*B, volume).

Where am I wrong?

Best regards, Piotr

```
```Piotr Wyderski
>In this short movie the guy explains the technology behind his 1kW LLC
>converter:
>
>https://youtu.be/wtcn6rZE1Eg
>
>At 0:57 he replaces a monolithic 16:2x1 transformer with 4 4:2x1
>transformers, which is a basic matrix transformer technology. OK.
>
>At 1:50 he merges two U-shaped transformers into a single E core,
>still fine.
>
>At 2:04 I got lost. He removes the center leg of the E core,
>basically returing to the U shape. But this is topologically
>equivalent to a toroid with 2x4 primary windings, in other words
>an 8:4x1 transformer. Since B=mu*H and H~N*I, he has flux doubling,
>not cancellation. He correctly concludes "half core size" (precisely,
>volume), but how did he get "half core losses"? Putting all the
>non-linearities aside, P_loss(B, 2*volume) ~= P_loss(2*B, volume).

I'd think, and I have not watched the movie, logic:
For example no core would be no core losses.
Depends on the frequency, sufficiently high frequency coupling does not need a core.

If you have an air coupled transformer,
then inserting a core would amount to RF heating it :-)

I am not going to watch that movie,
am training how it is to live with low bandwidth internet
now that I cancelled my cable subscription...
LOL

Usenet will still work with my Newsreader,
it was designed for that back in 1998.

hahaha

>Where am I wrong?
>
>        Best regards, Piotr
>
>
>
>
```
```Right, core is core, doesn't really matter.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

"Piotr Wyderski" <peter.pan@neverland.mil> wrote in message
news:po7bvb\$5f2\$1@node1.news.atman.pl...
> In this short movie the guy explains the technology behind his 1kW LLC
> converter:
>
> https://youtu.be/wtcn6rZE1Eg
>
> At 0:57 he replaces a monolithic 16:2x1 transformer with 4 4:2x1
> transformers, which is a basic matrix transformer technology. OK.
>
> At 1:50 he merges two U-shaped transformers into a single E core,
> still fine.
>
> At 2:04 I got lost. He removes the center leg of the E core,
> basically returing to the U shape. But this is topologically
> equivalent to a toroid with 2x4 primary windings, in other words
> an 8:4x1 transformer. Since B=mu*H and H~N*I, he has flux doubling,
> not cancellation. He correctly concludes "half core size" (precisely,
> volume), but how did he get "half core losses"? Putting all the
> non-linearities aside, P_loss(B, 2*volume) ~= P_loss(2*B, volume).
>
> Where am I wrong?
>
> Best regards, Piotr
>
>
>

```
```Tim Williams wrote:

> Right, core is core, doesn't really matter.

Thanks for confirmation, so another non-discovery.

Best regards, Piotr
```