Mains transformer goodness

failure

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But the primary is buried under the heavy gauge secondaries windings and then three layers of 0.05mm polyester film strip, each layer of that probably overlapped by a factor of 3. So I would have thought immune from any external mechanical effects, exccept vibration perhaps.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

This one is mounted by central coach bolt and dished disk plus rubber disk. In use the bolt is vertical and when amp is carried it is horizontal. I should say I've seen the result of an amp set for USA use used on 240V , extensive areas of bare copper due to lacquer melting or burning off and large amounts of smoke damage.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

"N_Cook"

** Now I know for sure you are a posturing BULLSHIT ARTIST.

The only thing that fails when a toroidal of several hundred VA is fed with double the rated primary voltage is the damn FUSE !!!!

..... Phil

Assuming the correct value/type of fuse was in place and hadn't been "repaired" by wrapping aluminum foil (aka ciggy paper) around it. In my experience not many 120vac transformers survive even momentary

240vac,fused correctly or not. Maybe you are talking about much larger transformers than I deal with. JC

** 100% WRONG !! ** So YOU only deal with flea powered trannys - right ? ** Did you bother to read what I posted ????

A dual-primary tranny of 300VA has 5 ohms of resistance if connected for

230/240 volts and 50 Hz operation

If the same tranny is connected for 120 volts - that 5 ohm value falls to a tiny 1.25 ohms !!!

When 240 is applied in error, the AC current draw is limited only by that

1.25 ohms of resistance - since the core is instantly driven into * total magnetic saturation* and effectively disappears.

The resulting AC current flow is in the order of **150 ** amps - so any tubular glass or ceramic fuse blows INSTANTLY.

Any domestic power circuit (ie thermal magnetic, 15 or 20 amp rated ) breaker will open in a few milliseconds under such a gross overload.

Get real pal.

...... Phil

,

with

It was someone who brought their 160VA Alchemist APD22 Nemesis Amplifier over from the USA, transformer survived long enough for the electrolytics to short , then they overloaded the primary enough to blow the , still set for USA use, mains fuse.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Why should anyone bother?

So the fuse should be about 2 amp slow blow type, which should blow within

0.1 sec at 20 amps and within 1 or 2 cycles at higher current. For 240 VAC use, it would be about half that. But the parallel primary connection would also be able to handle twice the current, so the fuse should have been adequate.

I have tested some toroidal trannies that seem to saturate quite slowly with increased primary voltage. In a 2 kVA unit rated 240 VAC I had about

50 mA at 240V, 100 mA at 280V, and 600 mA at 320V. Of course it would have drawn a lot more current at 2x rating, but perhaps not enough to blow a properly rated fuse instantly. I have seen a rather severe failure in a toroidal 480 to 240 VAC autotransformer that was connected backward to a high capacity mains source, thus placing the protective fuse on the load side.

Paul

would

I was trying to find a table or formula for toroidal inrush current versus power rating, but nothing found. A toroidal Tx , power for power comparison to conventional Tx, has to be larger fuse rating, to avoid blowing at switch on or after a few switch-ons. If a toroidal Tx has nothing wrong with it at switch one then there is more headroom for some later failure inducing problem not to blow the fuse. But does this headroom increase with higher wattage ? does the ratio of practical fuse rating/ normal maximum power consumption rise with higher wattage toroidals ?

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

"N_Cook"

** Has a 3 ohm primary.

Current draw on a 240 volt supply is circa 70 amps !!!

** Pure fantasy.

** Pack of lies.

The supply side fuse would have blown in milli-seconds.

The electros would not have be over voltaged.

..... Phil

"Paul E. Schoen"

** Not true of any normal commercial toroidal sold for use with AC supply, ** Memory plays tricks and your test results are probably wrong.

..... Phil

"JosephKK" wrote in news: snipped-for-privacy@4ax.com:

More useful for answering questions:

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

bz+spr@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

While it gives good background on PCBs it does not inform on the regulatory situation. Moreover some of the background is missing, like the presence of PCBs in varnishes and potting compounds used for ballasts and transformers. Also regulation wise very nearly all uses of PCBs are now banned. .

"JosephKK" wrote in news: snipped-for-privacy@4ax.com:

The wiki DOES mention the use of PCB as plasticizes in insulation, and gives a time-line for the production and use, thus gives us a good idea of which products might contain PCBs.

As a chemist (BS 1970), I have some familiarity with PCBs and the hazards and regulations associated with them. As a TEA Certified Electronic Technician, I have experience servicing electronic equipment. I also have practice in reading regulations. However I still found the Wiki much more useful than the regulations.

The simple fact that REGULATION WISE, the use of PCBs are now banned, in almost all cases, is easy enough to make without the reams of [almost] unreadable regulations.

If there is a particular SECTION of the regulations that you found particularly illuminating and informative, PLEASE point it out to us. My quick skim of the regulations did NOT give me any useful information other than PCBs are banned and must be disposed of carefully and under carefully controlled and regulated conditions. What point were YOU trying to make by citing that reference???

--
bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

bz+ser@ch100-5.chem.lsu.edu   remove ch100-5 to avoid spam trap

Gee, i did not find them unreadble.

No thanks, i already did that work twice for my cow-orkers. It was not worth it, they did not learn a darn thing. Twice burned by others whose job was to keep up with this stuff. .