Forums

Flux cancellation

Started by Piotr Wyderski 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