Theo it's SINCERE vs INSINCERE! That's all there is to it!

Yeah, well.. I guess it's what they're "sincere" about, isn't it?

Thanks!

 

As we all know, magnetic energy is not stored in an inductor's gap anymore than electrostatic energy is stored in a capacitor's dielectric ("soak" and piezo effects aside)! It's as saying electrical energy is stored in the "drop" across a resistor!
Well, you know it's that kind of lazy stupidity that makes me doubt the integrity of the physical sciences! Why must Phy Sci students suffer compulsory use of childish analogy and cognitive crutches on a magnitude unseen in any other area of study? So appreciation of reality is an unjustifiable extravagance as long as we can contrive a sanitized narrative fitting the model? Yeah! Right!

Theo I totally agree with everything you are saying except here

Why must Phy Sci students suffer compulsory use of childish analogy and cognitive crutches on a magnitude unseen in any other area of study?

Cuz being totally fair, severely dummified teaching is definitely NOT limited 2 just physical science!

Theo fwiw sometimes they do turnabout tactic! So for example idiotically convoluted _standard_ description of SSB modulation!
So properly described it's just up-conversion of AF signal to RF by mixing it with RF tone! So then tone (which some ppl clinging to pathetic analogy like to insist on calling _carrier_) is removed by nullification and unwanted sideband is filtered off b4 transmission (or conversion from like xmit _IF_ to xmit freq) that's it!
So standard description saying _carrier is removed at xmtr and reinstalled at receiver_ is perspective that's unnecessary and clouds issue! I say they're so hot on concept of _carrier_ that their intellectual cowardice won't let them lay it aside! So for ppl saying I'm being unfair holding technicians to standard of instructors all I can say is it's just wrong assuming technicians are morons and it's totally naive assuming all teachers are like saints! Ha! ha! I say @theodoravain proves fallacy of last assumption!

So abt SSB communication, here's true anecdote! I was branded _child prodigy_ for my description of that and other things like it at early age and I'm still suffering consequences! But I say truth is just that vry young ppl sometimes see things older ppl miss cuz vry young minds are still free from poisoning with cognitive biases and indoctrination!

Yeah, well.. I guess it's what they're "sincere" about, isn't it?

Theo o/c I mean sincere criticism instead of just trashing for sh_ts and giggles or advancing agenda to change intent of series! So first is easy to spot usually just by abusive language and second gives itself away with insisting on changing focus to non-problematic or already settled areas! So since errors and misunderstandings can be extremely annoying I always give abusive language or _harping_ on trodden ground a few chances b4 drawing conclusions! So it's like u and HP say we need 2 consider _course of conduct_ cuz I say _tough audience_ definitely does have _merit_ but they have 2b tough with sincere intent cuz otherwise it's like u say we're just practicing diplomacy and like forensic debate which isn't on curriculum

So to everybody HP says she's hoping 2b back on here soon but she says no promises cuz in her verbatim words _life is making her cry_ which I'm calling BS on that last part cuz HP never cries! So I say she prolly didn't even cry when she was born! But since that was more like rest of world's tragedy than hers why should she?

 

It's not like I walk around in a daze of "academic privilege"

magnetic principals

Theo! Ok! U totally have me convinced!

 

Theo! Ok! U totally have me convinced!

I'm probably the only fourth person in this forum who actually thinks that he/she understands what this is all about...

 

I'm probably the only fourth person in this forum who actually thinks that he/she understands what this is all about...

Cmartinez I'm just giving @theodoravain hard time for wrong word error (_principals_ instead of _principles_) so being fair it was probably fault of autospeller but I couldn't resist!

Now if ur more generally meaning stalled content that will totally improve when @Hypatia's Protege stops being delinquent little truant and gets back here!

 

Cmartinez I'm just giving @theodoravain hard time for wrong word error ...

. . Why thanks, Julia! ... and here I thought my posts were having the wrong affect... ... sorry, I meant to say "effect" ...

 

. . Why thanks, Julia! ... and here I thought my posts were having the wrong affect... ... sorry, I meant to say "effect" ...

@cmartinez on the topic of names, I'm helplessly compelled to ask (a thousand preemptive apologies) if you're related to Ursula Martinez? Sorry, no link! A second early patty-slapping might look bad on my performance evaluation.

Thanks!

 

@cmartinez on the topic of names, I'm helplessly compelled to ask (a thousand preemptive apologies) if you're related to Ursula Martinez? Sorry, no link! A second early patty-slapping might look bad on my performance evaluation.

Thanks!

Theo be nice! @cmartinez is like our last friend on AAC (or at least he was b4 your busybody questions)!

Theo anyhow I say coincidence of having same last name of like _exhibitionist magician_ is nothing compared to skeletons in YOUR closet which I can't even mention w/o getting banned or thread closed!

 

@cmartinez on the topic of names, I'm helplessly compelled to ask (a thousand preemptive apologies) if you're related to Ursula Martinez? Sorry, no link! A second early patty-slapping might look bad on my performance evaluation.

Thanks!

I don't know who she is, but if she has Mexican ancestry, then there's a chance we're somehow related. The Martínez surname was brought from Spain almost 500 years ago by two immigrants who arrived in the country 20 years apart. A Martínez was among the founders of my hometown, more than 400 years ago, and today that last name is held by more than 15% of the population in my city, which is about 4 million people.

​

See this pic? That's my fraternal grandfather ... I'm talking about the baby on the old man's lap. The man standing at the right is my great-grandpa, who was mayor of Monterrey during the 1920's, and to the left there's my great-great-grandfather ... the man holding the baby is my great-great-great-gramps ... he was probably born when Napoleon was fighting at Waterloo ... the picture was taken in 1901

 

I don't know who she is, but if she has Mexican ancestry, then there's a chance we're somehow related. The Martínez surname was brought from Spain almost 500 years ago by two immigrants who arrived in the country 20 years apart. A Martínez was among the founders of my hometown, more than 400 years ago, and today that last name is held by more than 15% of the population in my city, which is about 4 million people.

View attachment 150429​

See this pic? That's my fraternal grandfather ... I'm talking about the baby on the old man's lap. The man standing at the right is my great-grandpa, who was mayor of Monterrey during the 1920's, and to the left there's my great-great-grandfather ... the man holding the baby is my great-great-great-gramps ... he was probably born when Napoleon was fighting at Waterloo ... the picture was taken in 1901

Cmartinez I say it's totally awesome to have four generation photographic history of your family like that! As for my predecessors o/c I know my Dad and HP (my mom) and just barely remember my grandparents that's it! Not many pics of older generations either.

Now I'm thinking how rich a history our descendants will have now that everyone's obsessed with selfies and continuously updating blogs and statuses! Cuz in like 5,000 years ppl can look at pic of g.g.g.g.g.g.g.g.... Grandmom Aleph! And read intimate (hopefully not TOO intimate) details of my life and stream of consciousness

 

... read intimate (hopefully not TOO intimate) details of my life and stream of consciousness

not other people's consciousness, please! ... I can barely deal with my own already! ...

 

Theo anyhow I say coincidence of having same last name of like _exhibitionist magician_ is nothing compared to skeletons in YOUR closet which I can't even mention w/o getting banned or thread closed!

Who's talking family skeletons or dirty little secrets? We don't choose our relatives ya know.

which I can't even mention w/o getting banned or thread closed!

Beyond that my friend! How to politically sanitize this.. Got it! What you're contemplating would be as a round between "The Eagle" and "The Bear", at the end of the day nothing like a victor in sight, only regrets.

I don't know who she is, but if she has Mexican ancestry, then there's a chance we're somehow related. The Martínez surname was brought from Spain almost 500 years ago by two immigrants who arrived in the country 20 years apart. A Martínez was among the founders of my hometown, more than 400 years ago, and today that last name is held by more than 15% of the population in my city, which is about 4 million people.
View attachment 150429See this pic? That's my fraternal grandfather ... I'm talking about the baby on the old man's lap. The man standing at the right is my great-grandpa, who was mayor of Monterrey during the 1920's, and to the left there's my great-great-grandfather ... the man holding the baby is my great-great-great-gramps ... he was probably born when Napoleon was fighting at Waterloo ... the picture was taken in 1901

@cmartinez congratulations on your correct interpretation of my question's spirit! Really! Thanks!

Cmartinez I say it's totally awesome to have four generation photographic history of your family like that!

Absolutely!

Thanks!

 

Bridge Rectifier:
---Required Characteristics---
⇒Prv≥200V
⇒If(Continuous)≥30A
⇒If(surge)≥100A

Note that while an arrangement of four discrete industrial rectifiers is strongly recommended - A significantly less costly 'off the shelf' potted module exhibiting an I(fwd) Spec ≥ 30A (continuous) will suffice -- Be it known, however, that the recommended rectifiers or equivalents thereof (Ifwd=300A continuous/20kA surge) will easily survive protracted 'dead short' conditions whereas consumer-grade devices will undergo catastrophic failure prior to opening of even the fastest over current protection devices!

Typical industrial Si rectifier diodes (Ifwd[cont] = 300A, Ifwd[surge]=20KA, Prv = 1kv)

These should work just fine, for a considerable cost saving: http://www.mpja.com/04-16-18.asp?r=281268&s=3
The seller says there are 410 units in stock.

 

These should work just fine, for a considerable cost saving: http://www.mpja.com/04-16-18.asp?r=281268&s=3
The seller says there are 410 units in stock.

Yeah, thanks! I like the 150 Amp average/3.7 Kiloamp surge forward current rating. A bridge circuit of (your suggested) 15KR20As allows more wiggle room for better (lower ESR) filters than most integrated bridge packages I've looked at. For the information of anyone claiming "If overkill", I think many novices ignore the rectifier-stress implications of full-wave rectification and sizable filter capacitance.

@Aleph(0) Well, so ok! I received HP's memo. All that's clear to me is that she'd rather I not announce the exact day she expects to return to the project and interaction on this list? Why?.. Personally I doubt it (know better) but in the eyes of outsiders it's got to look non-committal at best and an awful lot like paltering and puffery at worst. Just saying!

Thanks!

 

The reluctance gap spacer will be fabricated from a small section of 0.01" (250um) PTFE sheet-stock (commonly available in bulk rolls as shown below).

A small suggestion, HP. Instead of using the soft-material standoffs as patterns for performing the cutting of the gap spacer, I'd suggest you use a pair of ordinary steel flat washers. It wouldn't matter if the washers were a bit larger or smaller than the standoffs.

With a bolt and a nut sandwiching the two metal washer together, it's a lot easier to firmly tighten the assembly and then use an x-acto knife or box-cutter to trim the excess material in a more precise way. A much more even cut finish would be obtained this way. It would also have the added advantage of not risking the integrity of the standoffs in the process. One could also add more than one layer of material so as to obtain several spacers at a time instead of just one.

 

A small suggestion, HP. Instead of using the soft-material standoffs as patterns for performing the cutting of the gap spacer, I'd suggest you use a pair of ordinary steel flat washers. It wouldn't matter if the washers were a bit larger or smaller than the standoffs.

Thanks! I like your suggestion! I believe HP will too. The curette/knife resistance of steel forms sound like perfecting our "improved" lathing process. Simultaneous fabrication of multiple spacers has a sweet ring to it too!

It would also have the added advantage of not risking the integrity of the standoffs in the process.

That's a nice thought! Sad fact is the AT is having lots of "fun" with misaligned standoffs and curetting them down along with the spacer material (the radius of the their tenth spacer is invariably visibly less than that of their first)

@cmartinez @The Electrician I've marked-up your suggestions to HP's HiPri index. FYI She expects to return to "substantial participation" (her words) on this list by month's end.

Thanks!

 

These should work just fine, for a considerable cost saving: http://www.mpja.com/04-16-18.asp?r=281268&s=3
The seller says there are 410 units in stock.

Electrician Tnx! It's totally perfect when right way can be economical way too!

A small suggestion, HP. Instead of using the soft-material standoffs as patterns for performing the cutting of the gap spacer, I'd suggest you use a pair of ordinary steel flat washers. It wouldn't matter if the washers were a bit larger or smaller than the standoffs.

With a bolt and a nut sandwiching the two metal washer together, it's a lot easier to firmly tighten the assembly and then use an x-acto knife or box-cutter to trim the excess material in a more precise way. A much more even cut finish would be obtained this way. It would also have the added advantage of not risking the integrity of the standoffs in the process. One could also add more than one layer of material so as to obtain several spacers at a time instead of just one.

Cmartinez tnx! Is like Theo says your idea can totally fix problem we're having! Cuz what we're asking them to do is clamp PTFE scrap between standoffs (just like in pix HP posted earlier on thread) but now with end of bolt in chuck of drill press then just lathe scrap down flush with standoff with #3 Sims UC. But they shave fraction of mm from standoff each time so subsequent spacers keep getting smaller and smaller So if rock beats scissors I say steel washer will definitely stalemate steel curette!

It wouldn't matter if the washers were a bit larger or smaller than the standoffs.

Cmartines that's right just as long as finished spacer diameter is ≤ (but not too much less than) center post on ferrite pot core (abt 13mm).

Well, so ok! I received HP's memo. All that's clear to me is that she'd rather I not announce the exact day she expects to return to the project and interaction on this list? Why?.. Personally I doubt it (know better) but in the eyes of outsiders it's got to look non-committal at best and an awful lot like paltering and puffery at worst. Just saying!

Theo it's just that HP is getting totally jumpy abt giving exact dates and deadlines cuz something always seems to happen to delay plans!

@Hypatia's Protege PLZ READ HERE! So on subject of LV PSU most ppl get that they can reduce filter-cap charge strain on SD xfmr and diodes by bringing on variac slowly! But a lot of them don't understand _connection at zero-voltage crossing inrush_ to variac (so pwr switch and line filter damage plus vry annoying fuse popping) is totally INdependent of wiper setting or load! I tried to explain it to them mathematically but most of them just don't get it So there's two points to this:

◊1 I know ur planing to suggest design of line synchronized power-up circuit but I say since LV PSU is just like u say _expedient_ anyhow we can just tell them to use inrush limiting thermistors! So it's not as elegant or instructional but like ur always saying we need to be keeping focus on main topic!

◊2 HP I say their difficulty understanding stationary inductor inrush is just another example of need for proper treatment of magnetics ASAP!

 

So on subject of LV PSU most ppl get that they can reduce filter-cap charge strain on SD xfmr and diodes by bringing on variac slowly! But a lot of them don't understand _connection at zero-voltage crossing inrush_ to variac (so pwr switch and line filter damage plus vry annoying fuse popping) is totally INdependent of wiper setting or load! I tried to explain it to them mathematically but most of them just don't get it So there's two points to this:

◊1 I know ur planing to suggest design of line synchronized power-up circuit but I say since LV PSU is just like u say _expedient_ anyhow we can just tell them to use inrush limiting thermistors! So it's not as elegant or instructional but like ur always saying we need to be keeping focus on main topic!

◊2 HP I say their difficulty understanding stationary inductor inrush is just another example of need for proper treatment of magnetics ASAP!

I explained the cause of the turn-on surge here: https://forum.allaboutcircuits.com/threads/how-transformer-work.88710/#post-642351

One disadvantage of negative temperature coefficient (NTC) thermistors: https://www.ametherm.com/inrush-current/inrush-current-limiters-full-line
is that they have a fairly long time constant and they get quite hot in the steady state. This means that if the power is turned off and then turned back on in a few seconds, there is no inrush limiting action. Using an NTC thermistor is a low-cost solution to be sure.

Since you're already recommending a process for turning on the power supply: "Turn the variac all the way down, turn on the power switch, turn up the variac slowly", you could add one more step.

Use two power switches in series, with one of them paralleled by a 5 ohm resistor. Let switch A be the one without the parallel 5 ohm resistor, and switch B be the one WITH the 5 ohm resistor. Add a step to the process: "First turn on switch A (the 5 ohm resistor is now in series with the line filter and limits inrush), next turn on switch B which will short out the 5 ohm resistor. To power down, reverse the order."

To be really fancy, one could have a mechanical arrangement to enforce the process.

If switch B is turned on with only a few seconds delay from the turn on of switch A, the 5 ohm resistor can be, say, a 10 watt rated resistor. If switch B is not turned on for a long time, the 5 ohm resistor will need a power rating so that the no-load current draw of the variac will not cause the resistor to dissipate more power than its steady state rating.

If the user doesn't follow the protocol then blown fuses and damage to switches may occur as is now the case. The cost of this addition to the process is one more switch and one power resistor.

This same function of having a resistor in series which then gets shorted could also be made automatic by using a time delay relay, for greater cost.

 

@The Electrician @Aleph(0) @HP

Yeah, ok I'm a magnetic imbecile so in keeping with that theme here's a pragmatic suggestion We could do this with a single 3 position switch.

1. Off (line disconnected).
2. Ballasted (line connected through a resistor in series with the variac).
3. On (resistor shunted, o/c you know it's vital the resistor is actually shunted without interruption of power to the variac)

Well now there are two obvious expressways to f'upsville;
1. Prolonged ballasting = overheated resistor.
2. Abbreviated ballasting = excessive inrush.

So.. Use of a line-voltage incandescent lamp as the ballast resistor (for inherent burnout immunity and visual inrush current indication) sounds like the fix. How about it?

Thanks!

 

@The Electrician @Aleph(0) @HP

Yeah, ok I'm a magnetic imbecile so in keeping with that theme here's a pragmatic suggestion We could do this with a single 3 position switch.

1. Off (line disconnected).
2. Ballasted (line connected through a resistor in series with the variac).
3. On (resistor shunted, o/c you know it's vital the resistor is actually shunted without interruption of power to the variac)

Well now there are two obvious expressways to f'upsville;
1. Prolonged ballasting = overheated resistor.
2. Abbreviated ballasting = excessive inrush.

So.. Use of a line-voltage incandescent lamp as the ballast resistor (for inherent burnout immunity and visual inrush current indication) sounds like the fix. How about it?

Thanks!

That would be ok as long as the contacts have a make-before-break characteristic and 20 amp rating.

I was thinking you could use standard wall switches and color switch A green and switch B red.