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Date: Wed, 14 Jun 2006 04:39:54 -0400
From: markusvester@aol.com
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To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: PA4VHF/p problems with core/high voltage etc
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Dear Dick, Jim,
 
as Jim pointed out, the flux density B scales inversely with the number of turns. As hysteresis losses go up with the cube of B, I would definitely tend to to stay well below 50 millitesla. I use a similar N30 core with 30 turns primary, it stays perfectly cool at 250 watts. Leakage inductance is not so much an issue for a narrowband LF application and can be minimized by multifilar winding. You will have to use thinner wire, but in your tapped autotransformer configuration copper loss will not be excessive.
 
73 and good luck
Markus

-----Original Message-----
From: james moritz <j.r.moritz@herts.ac.uk>
To: rsgb_lf_group@blacksheep.org
Sent: Tue, 13 Jun 2006 18:11:15 +0100
Subject: LF: RE: PA4VHF/p propblems with core/high voltage etc


...
There is a trade-off involved in the number of turns - increasing the number
of turns reduces the flux density and so the core loss, but increases the
loss in the windings. Also, having a large number of turns makes the leakage
inductance higher, and a small number of turns makes the winding inductance
too low.
...
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<HTML><BODY><DIV style='font-family: "Verdana"; font-size: 10pt;'><DIV>
<DIV>&nbsp;
<DIV>
<DIV>Dear Dick, Jim,</DIV>
<DIV>&nbsp;</DIV>
<DIV>as Jim pointed out, the flux density B scales inversely with the number of turns.&nbsp;As hysteresis losses&nbsp;go up&nbsp;with the cube of B, I would definitely tend to to stay well below&nbsp;50 millitesla. I&nbsp;use&nbsp;a similar N30 core with&nbsp;30 turns primary, it stays perfectly cool at 250 watts. Leakage inductance&nbsp;is not so much an issue for a narrowband LF application and can be minimized by multifilar winding.&nbsp;You will have to use thinner wire,&nbsp;but in your tapped&nbsp;autotransformer configuration&nbsp;copper loss&nbsp;will not be excessive.</DIV>
<DIV>&nbsp;</DIV>
<DIV>73 and good luck</DIV>
<DIV>Markus</DIV><BR>-----Original Message-----<BR>From: james moritz &lt;j.r.moritz@herts.ac.uk&gt;<BR>To: rsgb_lf_group@blacksheep.org<BR>Sent: Tue, 13 Jun 2006 18:11:15 +0100<BR>Subject: LF: RE: PA4VHF/p propblems with core/high voltage etc<BR><BR>
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<DIV class=AOLPlainTextBody id=AOLMsgPart_0_a71c9c04-80c7-4417-82b0-2f20b779470e><PRE><TT>...
There is a trade-off involved in the number of turns - increasing the number
of turns reduces the flux density and so the core loss, but increases the
loss in the windings. Also, having a large number of turns makes the leakage
inductance higher, and a small number of turns makes the winding inductance
too low.
...

</TT></PRE></DIV><!-- end of AOLMsgPart_0_a71c9c04-80c7-4417-82b0-2f20b779470e --></DIV></DIV></DIV></DIV>
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