[sdiy] How to predict a transformer's current capability?

[John L Marshall]

The holes in the corners are okay.

The lamiations reduce the eddy currents.

If you want the ultimate transformer, get a donut, a toroidal transformer.
Toroids do the best job of keeping the magnetic field where it belongs. The
core is powered iron for lowest eddy current. They seldom hum.

John


----- Original Message -----
From: Jaco Sloof <jacosloof at yahoo.com>
To: SynthDIYmailinglist <synth-diy at dropmix.xs4all.nl>
Sent: Monday, December 24, 2001 12:27 PM
Subject: Re: [sdiy] How to predict a transformer's current capability?


> Ok final question then;
> (sorry 4 al the stupid questions!
>
> (and then you guys say that there is no such thin as a stupid
> question, just stupiud answers, but i think im not really up to speed
> here... i just took the function of a transformer for granted, but i
> dont even really know how they function, even when i bui8lt my own
> electromotors... whahaha!)
>
> final question:
> do the mounting holes affect the effectiveness of the transformer,
> e.a: will maximum performance/stability raise if there were NO holes
> in the laminated core, or if it was'nt laminated, (with alternately
> precautions to prevent magnetic field (mf?) leakage?)
>
>
> Thanx guys for filling me in so far... this list is really
> educational, AND practical too!
>
>
> <status on my ASM-1: no progress yet, due to psu-design)
> <ok better then, status on psu-design:
> -PCB made, still gathering components, but its looking good
> -made a spice sim at a friends house, turns out its gonna be 650-700
> mA of current, really stable (10-30 mV ripple),
> or 1.5 A (30-80 mV ripple) >
>
> (am i crazy, designing my own voltage regulator out of discrete
> components?)
> --- John L Marshall <john.l.marshall at gte.net> wrote:
> > Mounting holes are cool. The gap of concern is across the magnetic
> > path.
> > Typical power transformers have primary and secondary winding on a
> > single
> > bobbin. E-laminations are alternated through each end of the bobbin
> > and then
> > meet an I-lamination. There is one magnetic path through the
> > windings and
> > two magnetic paths around the outside where the mounting holes are.
> > Least
> > flux densitiy in the corners of the rectangular core.
> >
> > ----- Original Message -----
> > From: Jaco Sloof <jacosloof at yahoo.com>
> > To: SynthDIYmailinglist <synth-diy at dropmix.xs4all.nl>
> > Sent: Monday, December 24, 2001 11:42 AM
> > Subject: Re: [sdiy] How to predict a transformer's current
> > capability?
> >
> >
> > > Hmm, gaps in the core...
> > >
> > > This concerns me a little bit, because:
> > >
> > > I'm still constructing my power supply, and
> > > the transformer HAS gaps, as in; mounting holes to screw it
> > > to the chassis, THROUGH the core...
> > >
> > > Is this Bad?
> > > (hole diameter is 4.5 mm, that on each corner thus 4 holes...)
> > >
> > > Rrrrr, i'm getting saturating shivers here, with lots a
> > background
> > > noise...
> > >
> > > --- harry bissell <paia2720 at yahoo.com> wrote:
> > > > You should be able to detect core saturation by
> > > > watching the current very carefully... as saturation
> > > > approaches the current increases very quickly... a
> > > > knee
> > > > similar to diode conduction (but going the other
> > > > way...
> > > > bigger!)
> > > >
> > > > Another way is to use a "telephone pickup coil" to
> > > > listen to the hum (flux leakage) around the
> > > > transformer. When the core saturates, the magnetic
> > > > field will grow in the air surrounding the core.
> > > >
> > > > This will also identify transformers that by design
> > > > or mistake, have substantial gaps in the core (usually
> > > > a bad thing...)
> > > >
> > > > H^) harry
> > >
> > >
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>
>
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