*>Jim, did you test using the Mag transformer with the larger AC wiring? Did
>you test using the Dahl transformer using the smaller AC wiring?
*
That was my first thought!
73
Jim W7RY
On Wed, Feb 10, 2010 at 6:08 AM, <TexasRF@aol.com> wrote:
>
> Jim, did you test using the Mag transformer with the larger AC wiring? Did
> you test using the Dahl transformer using the smaller AC wiring?
>
> In other words, how much of the problem is caused by the 12 ga wiring?
>
> Has anyone determined that a 22 ohm resistance in series with the secondary
> is enough to actually take care of the turn on surge? I ask this because
> many I have measured some of the Dahl secondary windings at about 25 ohms.
> Adding another 22 ohms only reduces the charging current by about half. In
> my experience, the charging current needs to be much lower than that.
>
> You mention pri magnetizing current: I am not familiar with that term and
> am guessing there is a 1.9 A current flow in the primary with no load on
> the
> secondary. If so, there is about 450 watts of loss just sitting there.
> Seems the transformer would get pretty warm when this happens. Am I
> understanding this correctly?
>
> I went through a voltage drop witch hunt in my shack a few years back and
> also found that 12 ga wiring for the power amplifiers is entirely
> inadequate. I ran a temporary length of 4/0 three conductor cable from the
> breaker
> panel to the amplifier area and that blasted cable is still there and in
> the
> way! I just have to get it out of there one of these days.
>
> 73,
> Gerald K5GW
>
>
>
> n a message dated 2/10/2010 7:24:54 A.M. Central Standard Time,
> Jim.thom@telus.net writes:
>
>
> I just ran a bunch of numbers on PSU designer and got quite different
> numbers than yours. I suspect it is because of the way measurements are
> being made. That is if I am doing things right here!
>
>
>
> Notice that with the 10 MFd filter and 22 ohm series resistor the Vo
> Drops 387 (multiplied by 100) volts from 267 ma load to 1.64 amp load.
> With a 100 MFD capacitor that voltage drop is only 149 volts.
>
> With no series resistor and a 10 MFD filter the voltage swing is 377
> volts. Only 10 volts better than with the 22 ohm resistor.
>
> But with the 100 MFD filter the voltage swing from 272 ma to 1.82 amps
> is only 59 volts without the 22 ohm resistor. This is about 100 volts
> better regulation than with the 22 ohm resistor.
>
>
> Should we not worry so much about low resistance windings on our
> transformers?
>
> ### Low resistance winding's on a plate xfmr are everything imo.
> A buddy just went through grief, using a NEW 46 lb mag cap xfmr
> for a 6m gs35b 6m amp. V regulation was terrible. Sure, there
> was a 6 v drop on the long 12 ga 240 line... but that same line
> power's his alpha too. [ not at the same time of course]. 700 v drop
> on the single tube 6m amp.
>
> ## The mag cap was changed out with a huge dahl xfmr,
> complete with 2 ga wire back to main panel and a string of
> 2500 uf new HV lytics. NOW, the V regulation is superb.
> Less than 150 v.
>
> ## I call the B+ voltage you get, when drawing ZSAC, the real
> NO load B+... not when on RX. Amp has to idle 1st... b4
> drive can be applied. [assuming NO EBS] OK, hit the PTT, and
> either pulse tune..or talk on ssb. B+ barely moves. PEP out
> of the amp is WAY up.
>
> ### Installing the 20-25 ohm resistor between FWB and B+ caps
> would have one good application though.... for step start. In that case,
> you don't have the problem of PRI magnetizing current flowing through
> the normal ..'resistor in one leg of 240 line' conventional step start.
>
> ## the mag current on some of my 4800 vac pole pigs is 1.9A
> IE: you can never fully charge the B+ caps up to almost full. I end up
> with one helluva big sec surge, when resistor in 240 line is shorted. The
> fix for now, was to reduce it's value. [25 ohms..down to 10 ohms]
>
> ## Now, installing the 25 ohm resistor, between FWB and B+ caps..
> this would be great for step start...THEN, short it out with a VAC
> relay !! Caps will charge right up to max B+
>
> ### Then, with vac relay present, it's a snap to toggle between..."22
> ohm resistor in line.. or OUT of line" I haven't tried the vac relay
> part
> ..yet.... but did install a 25 ohm, 225 watt, WW between FWB..and
> B+ caps.... and V regulation goes to hell..fast. The bigger the load,
> the worse it gets. Which is exactly what PSUD predicts.
>
> ## The test is repeatable. Try it yourself [with a big load... like
> either key down 1.5 kw out cxr... OR... just plane SSB.] It's lousy
> either mode..with that 25 ohm resistor installed.
>
> later.... Jim VE7RF
>
>
>
>
>
>
> Hope all the columns line up.
>
> 73
> Gary K4FMX
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|