[Prev][Next][Index][Thread]
Re: Multilayer Inductance
From: Mark S Graalman[SMTP:wb8jkr-at-juno-dot-com]
Sent: Thursday, September 11, 1997 6:04 AM
To: tesla-at-pupman-dot-com
Subject: Re: Multilayer Inductance
Hi Tom,
Yes of course you are correct, and I must apologize to Patrick. I
realized / remembered that about
a half hour after I hit the "send" key!! <G> I also had the 90 mH in
mind when I commented on the
excessive inductance for a 21" tall coil...........maybe I need some time
off?
Mark Graalman
On Wed, 10 Sep 1997 19:13:17 -0500 Tesla List <tesla-at-pupman-dot-com> writes:
>
>From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
>Sent: Wednesday, September 10, 1997 2:24 PM
>To: Tesla List
>Subject: Multilayer Inductance
>
>>
>> From: Mark S Graalman[SMTP:wb8jkr-at-juno-dot-com]
>> Sent: Wednesday, September 10, 1997 7:28 AM
>> To: tesla-at-pupman-dot-com
>> Subject: Re: New Coiler
>>
>>
>>
>> Hi Patrick,
>>
>> Here's my 2 cents worth:
>>
>> On Tue, 9 Sep 1997 22:22:57 -0500 Tesla List <tesla-at-pupman-dot-com>
>writes:
>> >
>> >From: Patrick J. Gustafson[SMTP:gustafpj-at-uwec.edu]
>> >Sent: Tuesday, September 09, 1997 4:12 AM
>> >To: Tesla List
>> >Subject: New Coiler
>> >
>> >Hello all,
>> >
>> >I have been patiently reading the list for quite some time now,
>but I
>> >could not get my questions to post on the list. Thanks to Chip,
>this
>> >problem has been finally resolved. Here are the concerns that I
>have
>> >as
>> >of yet:
>> >
>> >
>> >1. I have a two layer secondary coil with 28 gauge wire close
>wound
>> >for 21.6" (both layers). The first layer is at 6" in dia. and
>the
>> >second layer is at 6.125" in dia. The calculated resonant freq's
>are
>> >108.71 kHz and 106.45 kHz respectively, and the calculated
>inductances
>> >are 91.84 mH and 95.49 mH also respectively. Now since I layered
>in
>> >parallel, can I add together the inductance values directly? (
>i.e.
>> >the
>> >new value would be 187.33 mH)
>>
>> No, when inductances are placed in parallel the total value
>goes down
>> and will be less than
>> the least value of inductance, in this case the total inductance
>would be
>> about 46.8 mH
>>
>>
>snip
>> Mark Graalman
>>
>
>Mark,
>If the two coils were parallel in the usual fashion, meaning placed
>side by side with their ends connected, then what you wrote would
>indeed be correct. However, when a coil is wound ON TOP of an
>existing coil, the inductances are NOT in parallel, but rather
>co-axial. In this arrangement the effective wire SIZE is increased,
>but the inductance remains the same. Think about it carefully and you
>will see that such an arrangement is really the same as winding the
>coil with wire that is larger, or like Litz wire, if you will. In
>this arrangement the inductance is a function of number of turns and
>diameter and length. Several members on this list have built
>multi-layer secondaries and verified that the inductance is
>essentially the same as a single layer version. What you gain is
>current carrying capability based on increased SURFACE AREA (not
>cross sectional area) at high frequencies.
>
>The fact that the inductance is not changed is not immediately
>self-evident. At least, it wasn't to *ME* the first time I came
>across it. Even though I am an electronics instructor and am normally
>very careful in how I look at things, I initially thought that such
>an arrangement would yield a lower inductance. I was wrong. When my
>electronics measuring instruments showed me that the inductance
>remained the same, it was only THEN that I looked at things carefully
>and saw what was really going on. It is exactly like winding a coil
>with Litz wire.
>
>Someone on the List is using this method for their Magnifier's
>secondary coil, and they also noted that the inductance is the same
>as for a single layer coil. One of the Berts, I believe. (Bert Poole
>and Wild Bill Emery?)
>
>Hope this helps.
>Fr. Tom McGahee
>
>
>
>