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Re: Measurements

Posted by mqracing (M) on June 26, 2006 at 21:52:09

In Reply to: Measurements posted by John Swenson on June 26, 2006 at 21:17:20:

Hi John:

where is the choke being used? Is it the first L in a LCXXXX type filter?

or is the first element in the power supply filter a cap input?

what is the raw dc supply volts off of the rectifier? my calcs assumed about a 600 volt supply (like you might use in a power amp) and that the choke was the first element in the power supply filter network. And that the choke would then see about a 300 volt ripple component directly off of the rectifier.

If you reduce the magnitude of the ripple component... or this choke is not used in that spot.... or you use a cap input.... or anyway in the world you can reduce that from 300 volts down to 28 volts.... then you have a new ballgame.

***************************************************************

So, life at 28 vrms (say even at 100 hz for foreign line frequencies) is much, much, much, much improved. take design A and instead of 300 vrms at 100 hz change just that to 28 vrms at 100 hz.... and here is what design A morphs into....

(all other parameters as specified for design A in earlier post)

in design A modified for 28 vrms... the total heating current is reduced from 1.47 amps rms to 137 ma rms.

the temp rise of the copper circuit is now 5 degrees C

the temp rise of the iron circuit is essentially zero calculate degrees.

the loss picture improves thusly;

the calc copper losses are now .22 (point 22) watts
the calc core losses are now .02 (point 22) watts

the flux density drops down to about 2300 gauss (from 14kg)

and now you have a unit that is loafing. The air gap is too large... and in fact the whole choke is too large...

that is why I said it is important to have all the correct information when embarking on a design. What fails miserably at 300 vrms obtains a healthy lease on life if operated at 28 vrms of supply ripple.

MSL

This post is made possible by the generous support of people like you and our sponsors:

Kimber Kable

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