Author Topic: EEVblog #1152 - 240V-120V=Magic Smoke  (Read 5690 times)

0 Members and 1 Guest are viewing this topic.

Online thm_w

  • Frequent Contributor
  • **
  • Posts: 860
  • Country: ca
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #50 on: December 11, 2018, 07:09:11 am »
You did not completely tear down/unwind the transformer, I would expect there to be one in the center. It likely just needed a few more seconds to trip since the whole mass has to heat up (one can see only the outer layer really got hot, the center windings don't have damaged insulation yet).

The thermal fuse is there more as a long term overload protection, not really appropruiate for this case although it's likely it would have tripped before things got melty enough to affect outside stuff (smoke is impressive, but it takes a lot more heat before there is a real risk of setting external stuff on fire).
This really needs a fuse on the input. Pretty crazy, never seen a direct input in a long time even on the cheapest Chinese crap I have.

Seems unlikely.  Generally its on the outer windings and the transformer would have some indication of one being inside (bump in the tape, or a label).

http://www.eevblog.com/forum/beginners/is-a-thermal-fuse-a-current-fuse-as-well/
https://eessential.blogspot.com/2014/11/product-failure.html
 

Offline Paul Moir

  • Frequent Contributor
  • **
  • Posts: 856
  • Country: ca
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #51 on: December 11, 2018, 07:31:35 am »
I reckon no one foresaw to run it at 240...
A dropped neutral in 120v countries is not an unforseen event.
What did seem strange to me is that UL hasn't got a lot registered under this category, and what is are mostly soldering guns and firesticks.  There is a Snap-On transformer based station.  But maybe they just don't do a lot of soldering station work.
I don't remember seeing a soldering gun of the transformer type having a fuse, but perhaps they do? 
 

Offline G7PSK

  • Super Contributor
  • ***
  • Posts: 3609
  • Country: gb
  • It is hot until proved not.
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #52 on: December 12, 2018, 03:04:16 am »
Either it is poor design or that is a knockoff Weller, just checked both my cheapie soldering stations one circuit specialist and a Bakon from banggood  and they both have fuses soldered to boards,so the Pace unit has a fuse drawer built into the IEC socket which not only has the fuse but also holds a spare but of course thats a lot more money. 
 

Offline glarsson

  • Frequent Contributor
  • **
  • Posts: 803
  • Country: se
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #53 on: December 12, 2018, 04:06:38 am »
It can't be a knockoff. A knockoff would certainly have a fuse.
 
The following users thanked this post: SeanB

Offline GeorgeOfTheJungle

  • Super Contributor
  • ***
  • Posts: 1431
  • Country: pl
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #54 on: December 13, 2018, 12:44:32 am »
Any fuse you add primary would need a certain voltage and current rating that is oriented on the devices operating voltage. So you´d have to install a 240V fuse in the 120V device... just in case?!

For the typical small glass tube slow blow fuse form factor, isn't a 240V/1A fuse the exact same thing as a 120V/2A 120V/1A fuse? It's an I2R device, V does not matter much (within reason).

Edit: typo.
« Last Edit: December 13, 2018, 11:09:29 am by GeorgeOfTheJungle »
 

Offline Kilrah

  • Supporter
  • ****
  • Posts: 1642
  • Country: ch
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #55 on: December 13, 2018, 12:48:05 am »
isn't a 240V/1A fuse the exact same thing as a 120V/2A fuse? It's an I2R device

Reread what you wrote, slowly...
 
The following users thanked this post: GeorgeOfTheJungle, Ian.M, SparkyFX

Offline SparkyFX

  • Regular Contributor
  • *
  • Posts: 218
  • Country: de
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #56 on: December 13, 2018, 01:44:07 am »
For the typical small glass tube slow blow fuse form factor, isn't a 240V/1A fuse the exact same thing as a 120V/2A fuse? It's an I2R device, V does not matter much (within reason).
I was of course writing this regarding the isolation voltage after it blew - with respect to arcs/transients and general safety aspects as Dave points out in his multimeter teardowns when it comes to CAT ratings. Even though this soldering station is not CAT rated, transient overvoltage does exist, probably damage the transformer directly (a fuse wont help with that), but any additional part needs to be able to handle it?

The nominal voltage rating on the fuse is given for isolation, not in relation to it´s current carrying characteristics. Obviously that´s not an "operating voltage" which it is supposed to permanently drop, it is a fuse - a safety switch and that is it´s isolation voltage. Come on!

The discussion is getting very abstract and theoretical. I´d say there is no right or wrong way to prepare a device for this, the scenario was not a use case in the first place, the risks stay with the party that imported it to the jurisdiction. Questions around device protection usually run down to what statistically is likely to the general safety - not the most extreme outliers.

Of course a dropped neutral that connected to the other phase can happen, but that would also mean you try to solder in the dark and the beer gets warm. :)
 

Offline Paul Moir

  • Frequent Contributor
  • **
  • Posts: 856
  • Country: ca
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #57 on: December 13, 2018, 07:00:12 am »
Of course a dropped neutral that connected to the other phase can happen, but that would also mean you try to solder in the dark and the beer gets warm. :)
You've got your soldering iron on, plugged into a split outlet.  You plug your new reflow oven to the other socket and turn it on.  There's a bad connection on the outlet's neutral that gets worse when you dump 1500W through it and it opens.
Know what you speak of.  ;)
 

Offline SparkyFX

  • Regular Contributor
  • *
  • Posts: 218
  • Country: de
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #58 on: December 18, 2018, 05:45:42 pm »
Split outlets and the code for them are a new-to-me concept, as i am on a different continent. So excuse the dumb question: isn´t a double neutral feed required for those, as the gauge needs to match the cross sectional area for the live wire anyway? I don´t know if cable with two gauges in one sheathing would be usual.. hence two live/two neutral would make sense.

But i think i get what you address: a floating neutral on a per outlet basis... a lower impedance load would be in series with the device at double (180° split) the operating voltage, shifting the voltage drop according to their impedance (guess 0.8A/12.5A nominal=224,6V/15,4V), while the current for both is drawn through the soldering stations feed line/transformer/switch/fuse*. A fuse could help with that, but it heavily depends which device and which kind of device is switched on first.

OTOH: If the other, unkown device had a higher impedance, the soldering station would have undervoltage, lower current.

House installation and devices are usually handled separate, as the device manufacturer can only cover his part, not the rest of the installation and vice versa.
 

Offline paschulke2

  • Contributor
  • Posts: 17
  • Country: de
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #59 on: December 19, 2018, 04:51:09 am »
What I would really like to know is, are the units which are intended for the European market, like the rest of the European Wellers, made in Germany.
They were – until 2016. In 2016 manufacturing was moved from Besigheim in Germany to Mexico and 130 workers were laid off in Besigheim.
 

Online SiliconWizard

  • Super Contributor
  • ***
  • Posts: 1482
  • Country: fr
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #60 on: December 19, 2018, 05:53:39 am »
According to the WE1010 manual (see here: https://media-weller.de/weller/data/OI/OI/WE1010_OperatingInstruction.pdf ), they claim compliance with EN 60335-1:2012. I took a look at it.
("Safety of Household and Similar Appliances, Part 1: General Requirements")

Interestingly, as Dave suggested, the EN 60335-1 doesn't *require* the use of any fuse or even any specific protection measures at the primary side. They may be used as a means of being compliant, but are not strictly required.

The fault conditions that are tested are ALL simulated while the device is powered at the *rated voltage*, except two. There is basically one test in which the input voltage is lowered until the device stops functioning, then it's raised again to the rated voltage - and the device should be back to an operating state (probably to simulate power cuts). The other is a surge test, but as the surge pulses are relatively short, the transformer probably takes the abuse gracefully, and the protections at the secondary side are sufficient...

To get away with not doing anything more, they probably selected a transformer that is already tested compliant to some UL standard, and documented the device's fabrication process. And there you go.

This is still dubious engineering practise, but the device is most likely compliant to the required standards indeed...
« Last Edit: December 19, 2018, 05:55:32 am by SiliconWizard »
 
The following users thanked this post: thm_w, SparkyFX

Offline Richy_T

  • Newbie
  • Posts: 1
  • Country: us
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #61 on: December 20, 2018, 08:44:04 am »

I can't see it clearly but is that a fuse cover on the bottom right?

From other pictures I've seen, that's a grounding point for an anti-static strap.

I think Dave should accept Weller's offer of the 240V version so we could see if it has a fuse. Though it's kind-of surprising that there's no one who can tell us for sure on here already.
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 2056
  • Country: ca
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #62 on: December 20, 2018, 08:52:34 am »
In the pic I see three leads and think a thermal fuse is in the 240VAC transformer:
http://www.eevblog.com/forum/blog/eevblog-1160-weller-responds/msg2051086/#msg2051086
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 27695
  • Country: au
    • EEVblog
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #63 on: December 20, 2018, 09:55:39 am »
I think Dave should accept Weller's offer of the 240V version so we could see if it has a fuse.

Weller had their opportunity to tell us that, I or anyone else shouldn't have to do that for them.
 

Offline udok

  • Contributor
  • Posts: 6
  • Country: at
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #64 on: December 21, 2018, 12:27:40 am »
Just for information:

My Weller WMD-3 240 Volt soldering station has a primary Fuse,
which is resetable.
It is a rather expensive Schurter T11-211 1.5A.
 

Offline Clear as mud

  • Regular Contributor
  • *
  • Posts: 107
  • Country: us
    • Pax Electronics
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #65 on: December 31, 2018, 01:55:59 am »
Split outlets and the code for them are a new-to-me concept, as i am on a different continent. So excuse the dumb question: isn´t a double neutral feed required for those, as the gauge needs to match the cross sectional area for the live wire anyway?

As you said, the two live wires would be 180 degrees out of phase, so when both are in use, the current in the neutral would subtract, not add.  A single neutral is all that's required, and it is the same gauge wire as the two live wires.

The electrical code in the US has become more strict in this in recent years.  They call this a "multi-wire branch circuit," and you used to be able to legally run it off two separate breakers in the panel, of course making sure that they were on opposite legs of the incoming service.  But now those breakers are required to have at least a handle tie, so one can not be shut off without also shutting off the other.

Personally, I still like the idea of using multi-wire branch circuits, for conservation of resources and operation of the circuits with lower voltage drop.  Particularly in a commercial setting with wires running through conduit, if you follow the code requirements on de-rating ampacity when you have multiple conductors in the same conduit, you can really save a lot of materials if you use multi-wire branch circuits.  For instance, on a 3-phase system, 3 circuits can share one neutral and only count as 3 current-carrying conductors (because the neutral current cancels out, at least when driving linear loads that don't introduce harmonics).  But if you ran each of the three circuits with its own neutral, you have to count it as 6 current-carrying conductors, and then you have to increase the size of conductor because you have to de-rate the amps rating when you have so many conductors in one conduit.  NEC Table 310.15(B)(3)(a).  Then you have to increase the conduit size because the conductors are bigger.

The Code has been evolving towards prohibition of multi-wire branch circuits with shared neutrals.  Many electricians and electrical system designers now like running each circuit with its own neutral for greater reliability (not having to shut off multiple circuits to work on one) and less danger in case of an open neutral.
 

Offline Clear as mud

  • Regular Contributor
  • *
  • Posts: 107
  • Country: us
    • Pax Electronics
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #66 on: December 31, 2018, 02:35:03 am »
there were identical power outlets next to each other

I found where you told this same story before, but with more detail:
https://www.reddit.com/r/talesfromtechsupport/comments/5cgzcy/one_of_the_worst_nights_of_my_life/d9wxgdc
 

Offline janekivi

  • Frequent Contributor
  • **
  • Posts: 346
  • Country: ee
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #67 on: January 20, 2019, 10:08:04 pm »
I got very expensive station when working in telephone company, it is 25 year old...
actually it never was at work - I was using it only at home : ) Mains fuse is located
at front panel there, never looked inside or opening the fuse.
https://commons.wikimedia.org/wiki/File:Loetstation_Weller_WTCP-S.jpg
I had similar blue alpha Rosin Core solder wire reel... sweet smell.

But my hi-tech new soldering station doesn't have any fuse, even protective sleeves
are loose on mains connection. "Hakko'd" together from UPS transformer, clone front
panel and HAKD 907 handle.
I don't know who to blame...
: )))
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 2056
  • Country: ca
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #68 on: January 21, 2019, 06:17:55 am »
No ground or fuse, on/off switch? Think of all the money you saved.
Maybe Weller is hiring? They are looking for people like yourself  ;)
 
The following users thanked this post: janekivi

Online SiliconWizard

  • Super Contributor
  • ***
  • Posts: 1482
  • Country: fr
Re: EEVblog #1152 - 240V-120V=Magic Smoke
« Reply #69 on: January 23, 2019, 01:11:29 pm »
Maybe Weller is hiring? They are looking for people like yourself  ;)

 ;D
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf