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Re: Magnetic Rectifier??



Original poster: "Sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi All,
         These things sound exactly like a saturable reactor, basically an 
isolation transformer with an extra DC winding on it. DC is thrown across 
it to drive the core closer to saturation, so the inductance falls and more 
AC current flows.  I've seen these used to control big AC motors, but I've 
never scoped the output (no opportunity).  It does for AC current what a 
variac does for AC voltage. Wether or not it's suitable for making even 
trashy-humming DC, I'll stick with a 40kv2A fullwave rectifier made of 
1N4007's.  Chock full 'o ripple, but it's good DC. :)
Just my $.02
Shad G2-1203


At 08:32 PM 3/2/02 -0700, you wrote:
>Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
>
>Tesla list wrote:
> >
> > Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
><evp-at-pacbell-dot-net>
>
> >         Are you saying that a reactor, with the core saturated in one
>direction
> > by a DC magnetizing force or a permanent magnet will have a steady-state
> > DC component in the current which can flow through it when an AC voltage
> > is impressed?  Gotta think that through some more, but don't see how
> > that could happen.  Don't have a simulation program which includes a
> > model for saturation, and am trying to figure out an EASY experiment.
> > Gave plenty of magamp cores of all sizes, so might be able to rig it.
> > More discussion please.
>
>The idea is to insert an inductor in the AC path, that has an extra
>winding where a DC current is applied (a magnetized core would work too,
>but a DC current adds easy control). A transformer with AC in one coil
>and DC in the other. The inductor would normally
>present a high impedance to the AC circuit, with little current flowing
>through it. When the sum of the magnetic fields produced by the DC
>and AC currents causes the inductor core to saturate, the inductance
>falls to a low value, and the AC current flows more intensely.
>Since the bias is DC, the "inductive switch" will operate at just one
>side of the AC cycle. The resulting current will look as a small AC
>waveform (sinusoid) with high current pulses at the centers of the
>swings of one polarity. The width of the pulses can be controlled by
>the DC current. These devices are very robust, although not very
>efficient. I have seen they used in (rather old) high-power battery
>chargers, with a diode connecting the AC+pulses current to the
>batteries.
>(Without the diode, the battery would generate a DC current flowing
>back through the inductor and the AC power transformer, limited only
>by wire resistance).
>These devices are still used in many applications, including
>high-voltage
>switching.
>
>Antonio Carlos M. de Queiroz