[Amps] Toroid Plate Transformers

[Tomm Aldridge]

Ulveco makes a fine product.  Having been a magnetics engineer for 
Sprague and ADC for several years, I can tell you that  a toroid usually 
gives better regulation per unit volume than EI and C core designs.  On 
a toroid you do not fill the window as much as you do on an EI or C core 
so there is more iron and less copper.  High quality EI and C core 
transformaers (Dahl) are the equal of any, regardless of the form 
factor, as they are designed for great regulation.  A shortcoming of the 
toroid is its inability to withstand DC bias.  It has no air gap as does 
the EI or C core, which is needed to handle DC bias.  In circuits in 
which DC bias can be guaranteed to be zero, this is not a problem and 
the toroid exhibits another of its advantages, low magnetizing current 
and thus higher efficiency.

As to cost, for the highest manufacturing costs the toroid wins hands 
down.  THe core has to be taped and the wire has to be either hand wound 
or shuttle wound with expensive and fussy machines.  The EI and C core 
transformers are easy to wind on a pre formed plastic or paper former 
using esentially a cheap lathe with a turns counter and a regulator to 
stop at the proscribed turns.  Many coils can be wound at once as 
opposed to the toroid in which you dedicate one machine and operator to 
one transformer.

Skram, Helge (MED) wrote:
> Hi
> 
> In my experience, torodial transformers should be the choice for new
> designs.
> I have built several amps and until my last project used EI core
> transformers.
> These have been custom made here in Norway. 
> The cost is comparable with the P.Dahl Hypersil transfiormers.
> Would have been interesting to try one of these, however most are made for
> 60Hz, and that don't work well on 50Hz.
> 
> For my 50MHz amp with 8122, I wanted to try a custom made torodial from
> www.ulveco.no
> Maximum voltage they could make was 1000v. Setteled for 860v and voltage
> doubler, this gives 2.2kV loaded.
> This worked very fine and price was lower than EI core type from my usual
> supplier.
> Have now made a very compact and light weigth 8122 amp with 1/2kw
> capability.
> 
> You should really consider toroidals.
> I don't understand why they should be more expensive in USA.
> 
> 73
> 
> Helge
> LA6MV
> 
> 
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
> Behalf Of Bill Smith
> Sent: 4. desember 2003 16:06
> To: amps at contesting.com
> Subject: [Amps] Toroid Plate Transformers
> 
> 
> Toroid Coprporation of Maryland will manufacture
> Toroid power transformers for Hams.  I confirmed it by
> calling them.  They will be more expensive than
> traditional transformers unless you buy more than one.
>  Combining orders would be the way to go.
> Their web site is:
> www.toroid.com
> 73,
> Bill
> 
> =====
> Bill Smith KO4NR
> 
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