Diode in series with the mains

[N_Cook]

I use a variac with an AC ammeter in line. I like to heat test kit using
a hot air gun on low setting. But for the low heat range, a diode is in
series with the mains, the one-sided "switching" 50/60 times a second
causes horrendous magnetising current problems that would overheat the
variac I'm sure, used on the same mains ring main. Replace that diode
with a preset triac for balanced "switching" ?
I one time niaively thought putting a 1N4007 in series with a 50W, 24V
soldering iron Tx would give a low temperature iron for melting plastic,
ended up melting the 24V Tx.
What effect , if any , would such diodes in say hot air guns, falsely?
register on a moving disc mains kWh meter or the recent "smart" meters /
monitors ?

[Phil Allison]

Nutcase Kook wrote:

> I use a variac with an AC ammeter in line.

** On the output side?

> I like to heat test kit using a hot air gun on low setting.
> But for the low heat range, a diode is in
> series with the mains, the one-sided "switching" 50/60 times a second
> causes horrendous magnetising current problems that would overheat the
> variac I'm sure, used on the same mains ring main.

** You are exaggerating a bit.

> Replace that diode
> with a preset triac for balanced "switching" ?

**Could be a gotcha there - how does the fan get its power?

In my old Black & Decker (Made in England) 1600 watt gun, the DC fan runs via one diode from a tap on the main heater winding. The half power diode has the same wiring polarity so fan operation is not stopped at half setting.

Fit a triac and the fan would lose half its power, so the air would be just as hot with either setting.

> What effect , if any , would such diodes in say hot air guns, falsely?
> register on a moving disc mains kWh meter

** Suspect half wave loads make them under read a bit.

Why not try it out while counting turns on the big wheel




.... Phil

[jurb...@gmail.com]

I don' get it. There have been half wave recifiers off of transformers for a long time and I never heard of this. Does the full wave rectifier let you use a shittier transformer ? the only mechanism by which half wave rectification can do anything bad to the transformer is by core saturation. Then you lose inductance and we all know that story.

>"** On the output side? "

If we are talking core saturation here, it probably doesn't matter much. Anything polarizes the core's magnetic field should do it, but it should be based on current. No load, no problem.

>"**Could be a gotcha there - how does the fan get its power? "

That motor draws only a small fraction off the current compared to the heating element. However alot of them DO use a diod for low power, what else ? A resistor would melt the thing and a chopper would just be too much because alot of them are cheap. I don't care if you pay alot for it, that just means they made more money.

>"** Suspect half wave loads make them under read a bit. "

My Uncle and cousin (his son) tried to do just that. Both into electronics and with better jobs than I actually. But they did it big, the went to shithouse (ESI in Cleveland back when they were in Cleveland, a surplus place) and got these gnarly rectifiers and hooked them up to the elements of an electric furnace. They said it was weird like you could see waves going through the elements when they were first getting up to temp. But the idea was to magnetize the poles/stator or whatever and slo the thing down permanently, or nearly. There is no way to know if they had any success but it was a fun thing they did as a Father/son project. Hey, we never promised to use our powers for good. >-)Youse guy down there don't think that way because they don't fuck you up the ass the way they do here. Our morality is to return the favor until we get caught and then get a good lawyer. In fact the reason so many onventors came here is because of the market and the intellectula property laws - i.e. MONEY.

>"Why not try it out while counting turns on the big wheel "

That would require separating the load. I used to have a watthour meter but the person's brother who supposedly sod it to me took it. My choices were to shoot him or call the law, and I was pretty sure that watthour meters were not available at the local store. It was probably stolen. these fuckers used it to charge people on their (tube) TV repair bill for test run time. they used to pull like 300 watts and runiong them for eight hours a day lookig for an intermittent cost money. They also were the first ones I know of in the area that charged for chemicals when cleaning pots and switches.

Two brothers. One would NEVER pad the parts. He would write a bill with $4.00 parts and $68 labor. theyu other used to but switched to charging "installed" prices and trhe labor became "technical serbvice time" which is supposedly the time to troubleshoot. Of course if the job is done in fiveminutes they still pay.

But I am sure a watthour meter can be had. So many of the old style ones have been retired from service that somewhere they must be on eBay or something. I doubt they differ much, in fact you might want a US one because it is designed to be accurat if half the line is loaded or the whol thing. In other countries it is all one sided.

Of course that means for the best results in the US we need a rectifier on each side, going opposite directions so it rectifies the same phase of the cycle. Well if you want to run your whole house on it.

With newer technology, I bet one could take that rectified 320 volts, build a nice switcher and do just that and run everything. How long you figure before they become illegal ?

Or even thosse frequeny convertors that do not rectify, but just use the AC from three phases to pretty much cleanly convert to a higher frequency for VFDs ? Just redesign it to only use one half of the cycle. Those run on three phase and they have to to do what they do because there is always voltage. But we are not converting frequency here. this is just getting AC out of DC.

I am not so sure that can be done. ?Have to give it some thought when summer comes and it it air conditioning time. That costs quite a bit less since I changed the run cap in the condensing unit. but now, that thing take 240. What's more it takes quite a bit of amperage and we still have the old style motor driven meter.

And, if I can't make it sinosodial, will that just decrease the efficincy to the point where I just wasted my time ?

I dunno. Going out for a smoke.

[Phil Allison]

jurb...@gmail.com wrote:

> I don' get it. There have been half wave recifiers off of transformers for a long time and I never heard of this.

** You have misread what the thread is about.

>
> >"** On the output side? "
>
> If we are talking core saturation here,

** You have misread my post.

Re-boot and try again.



.... Phil

[N_Cook]

Diode on the mains primary side of the heater wire of the hot air gun,
for a lower power setting. Then something corrupting going along the
mains wiring to the variac at some other point on the same ring main. I
was forgetting there is RCCD in there as well as the variac (for extra
personal protection). I think a bit more testing of the mains wiring and
temporary removal of the trip is in order.

[hrho...@sbcglobal.net]

Diodes I ever seen are always on the secondary side of the transformer.

[Phil Allison]

hrho...@sbcglobal.net wrote:


> Diodes I ever seen are always on the secondary side of the transformer.

** Everyone is MISSING the point here.

The *diode* in question is INSIDE the hot air gun !!

Using it produces an ASSYMETRICAL load on the AC supply.

That in turn produces a small DC OFFSET in the supply - maybe 0.5 to 1 volt.

THAT in turn causes partial core saturation, particularly with TORROIDAL transformers, on the same supply circuit.

When did a toroidal come into the picture ?

WTF do you think a Variac is??

FYI"

The Nutcase Kook Troll **NEVER** explains anything he posts.




.... Phil

[Chris Jones]

Not directly relevant to this discussion, but I am reminded of this
story. Perhaps you'll like it:
https://www.youtube.com/watch?v=G_yBBAV3HyM#t=358