PRR

Re: Two 110V devices on a 220V outlet
« Reply #20 on: September 29, 2018, 07:47:04 PM »
> most smaller transformer based 110 volt adapters arent in fact galvanically isolated

The tiny "traveler" converters may not be.

The heavy yellow lump you imaged in #16 is NOT fully isolated; it delivers 110V Center-Tapped at Earth (55V each side). It is made for UK construction sites. It makes it hard to kill a wet carpenter.
https://www.its.co.uk/blog/buying-guides/what-is-110v-do-we-need-it/
https://www.blakley.co.uk/transformers/construction-site-transformers-3kva-20kva/portable-tool-transformers-3000va-5000va
https://www.tester.co.uk/tools-and-accessories/110v-site-construction-equipment/110v-transformers-converters

I *believe* the 3rd-pin PE is wired around from the 230V side to the center of the 110V side and the 3rd-holes of the 110V outlets. This preserves your buzz-reducing ground path. I have never actually fondled one of these yellow lumps (shipping would be brutal) so verify for yourself.


Youngwhisk

Re: Two 110V devices on a 220V outlet
« Reply #21 on: September 29, 2018, 11:46:46 PM »
This is acceptable in my location, providing the two breakers are connected or have a tie bar on them..

https://www.electrical-online.com/wp-content/uploads/2012/01/kitchen-split-receptacle-connections.jpg
« Last Edit: September 29, 2018, 11:49:51 PM by Youngwhisk »

PRR

Re: Two 110V devices on a 220V outlet
« Reply #22 on: September 30, 2018, 01:29:27 AM »
> This is acceptable

Because it has HARD 120V source(s), the White wire, among the 240V lines.

In US and Canada (a few other places) the WHOLE house is wired this way: 120V and 240V. (The bit about tying the breakers is only when you save copper by feeding two separate 120V loads through a single cable, and "only" for safety when working on the cable.)

OP is in Belgium. They do not have a 120V line, only 230V.

saint gillis

Re: Two 110V devices on a 220V outlet
« Reply #23 on: September 30, 2018, 04:51:20 AM »
OP is in Belgium. They do not have a 120V line, only 230V.

No pbm, go ahead, I'm asking more for educational than practical reasons. Btw how an autotransformer works? I mean  how can can we get half the source voltage through such an inductances network?

Re: Two 110V devices on a 220V outlet
« Reply #24 on: September 30, 2018, 09:25:33 AM »
I had written another post ,but forgot to send it I think .

Yes of course I remember now the yellow transformers are 55v from either leg to ground ,and not isolated .Makes any chance of a lethal shock much less , So as you were saying Prr .in the US you get the 240 from the lines ,then each dwelling has its own build in stepdown to deliver the 110 to the sockets ? Does the 240 volts actually appear to the customer , or is the non transformer outside 240 volts just used for appliances ,like for instance a cooker ,or other potentially heavy loads?

JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #25 on: September 30, 2018, 12:34:18 PM »
No pbm, go ahead, I'm asking more for educational than practical reasons. Btw how an autotransformer works? I mean  how can can we get half the source voltage through such an inductances network?
Autoformers do not galvanically isolate primary and secondary with two windings, instead the primary and secondary are connected. For voltage step up the extra boost winding is stacked on top of the primary, so boost voltage is added to the mains input voltage giving it a head start and higher efficiency (smaller transformer flux/core).

Step down is less simple but the lower voltage is tapped from within the primary winding... the current flowing in the primary winding contributes to the lower voltage output tap.

The iconic Variac, variable AC voltage supply, is generally performed using an autoformer.

Since the secondary is not floating, these are more dangerous, but mains voltage is always dangerous.   

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

saint gillis

Re: Two 110V devices on a 220V outlet
« Reply #26 on: October 01, 2018, 04:53:23 AM »
Ok so they also use electromagnetic induction, but the windings are in contact..

Re: Two 110V devices on a 220V outlet
« Reply #27 on: October 01, 2018, 10:30:52 AM »
Ok one more shot at understanding US mains power , so 120v comes from the lines ,into a transformer in the house ,on the secondary  theres two 120v windings ,in series ,one side to neutral ,one wire for 120 volts and another for 240 ?
Are you free in your house in the states to have plug sockets that deliver 240 volts to consumer equipment etc or is the 240 only for for things that are permanently wired in and not plugable ?

JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #28 on: October 01, 2018, 11:18:05 AM »
Ok one more shot at understanding US mains power , so 120v comes from the lines ,into a transformer in the house ,on the secondary  theres two 120v windings ,in series ,one side to neutral ,one wire for 120 volts and another for 240 ?
Are you free in your house in the states to have plug sockets that deliver 240 volts to consumer equipment etc or is the 240 only for for things that are permanently wired in and not plugable ?
Most residential service is a single phase (electrical power term, high voltage distribution uses 3 spaced phases of power) transformer winding of 240V with a center tap, so two nominally 120V legs WRT that center tap.  Only at the service drop (fuse box, circuit breakers, whatever), that center tap is bonded to neutral (mains 0V), and earth ground. 

Inside the house you can find 120V outlets and a few specialized 240V outlets (different blade pattern so 120V gear cannot plug in).  My 240V wall oven is hard wired to 240V (across both 120V legs) but my through wall air conditioner uses a 240V plug and outlet, likewise my laundry room dryer uses  a 240V plug/outlet.

As Paul shared a faulty neutral bond to this transformer winding center tap can cause one side of the now floating transformer winding to load down, driving the the other leg to higher voltage.  This is not a common fault, but happens enough to worry about it.
====
Decades ago when I was experiencing a high mains voltage event (my then incandescent light bulbs were unusually bright), the first thing I did was measure across the two legs inside my fuse box to confirm I didn't have a floating neutral (I didn't).  The local power company was mildly irritated when I called them that night (what do dumbass customers know?), but I was insistent and the guy on duty that night drove 20+ miles out to my house and measured the voltage at my power drop... it was high.  8)  He then drove a few miles up the road to the power substation and unstuck the huge auto-former there that tweaks line voltage up/down as load varies during the day.  If he didn't unstick it, who knows how high the voltage might have climbed as more customers shut down for the night?  :o

He didn't thank me, but I probably saved the utility some money from damage claims if they blew up customer's appliances with over voltage. I was already reading 260-270V and climbing on my 240V drop. 

JR


Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: Two 110V devices on a 220V outlet
« Reply #29 on: October 01, 2018, 12:02:50 PM »
Thanks John that makes more sence ,

So am I right in saying that even though its only single phase delivery from the supplier ,you do have two seperate 110v phases from either side of the transformer in the circuit in the house and 240 is taken from either end of that ?,   that did lead to the question we dealt with earlier on load sharing between windings and voltage drops , slightly different situation to having two seperate cores across mains with vastly different current .
Will heavily loading one leg of the 110volt cause a tip up in the other side if its lightly loaded ?    In other words lets say something big fuses out, the moment the fuse goes ie a short circuit ,would everything on the other 110v leg not get a surge or will it just tend to pull the voltage down also ?



PRR

Re: Two 110V devices on a 220V outlet
« Reply #30 on: October 01, 2018, 12:12:04 PM »
> .in the US you get the 240 from the lines ,then each dwelling has its own build in stepdown to deliver the 110 to the sockets ?

What JR said. Power on the street is 20,000V, which is not brought to customers. A 20KV:240VCT transformer at the street(*) feeds one to eight houses with center-tapped 240V, 120V each side.

We have three conductors in the cable from street to house. We have three buses in the fusebox, 120V/0V/120V.

Lights, radios, home toasters are all 120V. "This was safer" (in days before good rubber, and now we are stuck with it). A 120V outlet is connected to one 120V bus and the 0V bus.

Dryers, water heaters, large heat/cool systems (starting from large motors in Edison's 100V/200V DC system) take 240V and are wired from one 120V bus to the opposite 120V bus, making 240V.

In addition the CT of the 240V is connected to Dirt various places, hit-and-miss. (There's rules but they get neglected.) So we nominally have only 120V To Ground. Where you have 230V and a UK carpenter may have 55V to earth. (On smaller sites UK guys use 230V tools and trust a RCB.)

(*)The HV:240VCT transformer location varies. When possible it is on utility right of way. In cities, on a street-pole or transformer vault. Large factories and malls have the 20KV brought to a transformer in the yard, and may distribute at 240VCT or may run 440V or 600V to heavy loads.

At my house a can on the street pole feeds me and the guy across the street. My house line is at the upper end of what is economic at 240V 100A, and my lights sag. My side neighbor a little behind me has 20KV come up his driveway (burning branches) and a transformer on a pole 70 feet from the house. My other side neighbors, and extended family, bought a huge hunk of land and will build 1/2 mile from the street. They are getting 20KV brought in over a dozen new poles, and I assume a couple transformers near the houses.

> heavily loading one leg of the 110volt cause a tip up in the other side....

A perceptive question. "It Depends". For 99% of customers, negligible. Line voltage drop is typically small, so unbalance has small effect. OTOH this system may use more copper. On my too-long line, unbalance can be seen (well-pump start on one side makes half the lights *brighten*). However wildly unbalanced loads are rare. A typical house gets 24KW @ 240V  and 120V loads don't go past 2KW. 120V outlets are distributed to both buses. You would have to work it out to manage to get all your 120V loads on one side.


JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #31 on: October 01, 2018, 12:56:58 PM »
Thanks John that makes more sence ,

So am I right in saying that even though its only single phase delivery from the supplier ,you do have two seperate 110v phases from either side of the transformer in the circuit in the house and 240 is taken from either end of that ?, 
This may be a little confusing power industry jargon but the two opposite polarity ends of the center tapped 240V winding are considered the same "phase", since they come from one phase of the high voltage distribution.

If you look at major HV distribution systems the poles have 4 wires. 3 wires symmetrically spaced and energized to high AC voltage but phase shifted 120' apart.  The 4th wire generally lower on the pole is ground (AFAIK but don't touch it  :o ). 

Inside factories and facilities that use lots of power, the electricians have to keep track of the three phases.
Quote

 that did lead to the question we dealt with earlier on load sharing between windings and voltage drops , slightly different situation to having two seperate cores across mains with vastly different current .
Will heavily loading one leg of the 110volt cause a tip up in the other side if its lightly loaded ?    In other words lets say something big fuses out, the moment the fuse goes ie a short circuit ,would everything on the other 110v leg not get a surge or will it just tend to pull the voltage down also ?
It depends... in theory the two legs share a common magnetic flux, so loading one should load both, but this ASSume zero impedance neutral wiring path... depending on how you measure things, drop in the neutral path wiring can affect voltage readings elsewhere.

JR

PS: Coincidentally I lost power two mornings in the last week or so (unusual). The second morning I recognized one of the power workers across the street from my house (a kid I played basketball against at the church years ago). I talked with him some. The first power outage was caused by limbs from an old oak tree a few blocks away that took out the whole town, that morning's outage was the more common squirrel blowing a fuse (these fuses sound like a gunshot when they blow, the squirrel doesn't fare well). He shared that he was recovering from a broken back he got when he fell off a power pole several months ago. Luckily he expects a full recovery but feels older trying to recuperate and play ball. He is not a dumb kid, but stuff happens and probably a little smarter now. I've seen these workers out in the pouring rain replacing high voltage fuses up on the power lines using just a long fiberglass extension pole. I would never do that (in the rain). Luckily we don't have to. 
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: Two 110V devices on a 220V outlet
« Reply #32 on: October 01, 2018, 03:33:49 PM »
Thanks Prr and John,

The whole electrical safety and differences between the US and European systems is an interesting subject , and the discussion is never wasted on anyone new or old to electronics . Theres no doubt the American system when used correctly is inherently safer ,both with lower voltage ,and the limits the domestic transformer place on source impedence, I cant help but think in the hands of fools it has the potential to end up very much more dangerous. Euro volts come direct courtesy of what ever VA transformer you have in the neighbourhood ,pole mounted 50kva are most common in outlying areas ,estates and built up areas have huge oil filled ones  .
12KV is the line voltage on the three wire system near me ,once the fuses blew out on the pole in my garden ,I managed spot  the issue before calling  in the fault  , when the guy arrived I pointed him out the fuse , he told me I should probably apply for a job with ESB , looking back the originally state funded 'electricity supply board' of Ireland was a very very good job indeed ,I know several people who worked for them , its more or less semi state now or maybe even a private enterprise ,the vast majority of which is owned by its shareholders who are also its workers and ex employes,  A lot of power generation here now is being farmed out to various other opperators ,wind farms especially ,but good old ESB still owns and maintains the infrastructure itself so they get to collect till kingdom come. A relative of mine worked with them as a chemist  for many years , Its my guess the pensions were meticulasly managed in such a way that the bigger and more sucessfull the company got , the more the pensions payed out end of day ,and that even former employess still gain  long into their golden years as the company goes from strenght to strenght. Its like a special feedback loop that keeps the worker/holder chomping at the bit and retired employee is more or less immune speculation worries and juggling investments to keep pension together .Nice card game for those who got in on it .

The big yellow ISo's here also come in a 1:1 variety for safer opperation of common domestic tools  ,its denoted with blue coded recepticles , Would there be  any benefit to me supplying mains power via a 1:1 3kva site transformer to sound equipment with centre tapped to ground 230V output, in terms of mains borne noise and switching spikes voltage fluctuations ? For the sake of 30-50 euros for a good/used site iso transformer is it something worth adding to the power supply to my shed  both for an increased safety margin and because it will help supress mains gash ,and maybe also allow me to define my own ground locally ?

JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #33 on: October 01, 2018, 04:35:18 PM »
There's lots of voodoo magic attributed to mains power... Some people sell phools thousand dollar line cords. (Don't do that).

Product designers work to make gear impervious to typical power it will be exposed too... I recall at Peavey having to deal with world wide power... Several extreme areas... Both high voltage and low... Imagine in the outback of Oz sending power down miles of wire... cheaper to step voltage up at the send end to compensate for wire losses, but I've heard failure reports from crazy high mains voltage in OZ. Low voltage reports were mostly SA and Africa...

But I recall customers blowing up 220/240V products in the ME (middle east not Maine) by trying to use the rear panel 220/240 switch to adjust for low power in some flaky venues...  BUT applying 240V in the 220V switch position could release smoke (until I changed to higher voltage transistors in the amp module  ::)  The customer is always right, even when operating the product incorrectly).

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

PRR

Re: Two 110V devices on a 220V outlet
« Reply #34 on: October 01, 2018, 09:28:50 PM »
> two seperate 110v phases

The simplest AC motor will not start on 1-Phase.

Adding the 180 degree "phase", as from a CT transformer, does not help at all.

The most obvious way to power AC motors is to distribute two phases, 90 degrees apart. This directly gives the effect of a steam engine with two duplex cylinders on 90 deg cranks; always starts and runs smooth. At the worst case, this is four power wires and a ground wire; though much was done with two hots and an oversize "Neutral"/Ground.

The dwarf did some math and showed advantages in copper-utilization with three phases 120 deg apart. It's gotta be 100 years since any other system was used in new districts. It is how power gets around in large quantity over long distances.

3-phase has very little merit in "small" installations, houses to small shops. More wires and also more or more-complicated transformers. In my sparse residential area, 3-phase comes past use but as 2-phase (omitting the 3rd leg), and my street 20KV is all on one leg of that. The 1/2/3 trickery allows later up-grading IF this area ever grows- two wires and a 3rd transformer we could have apartment towers side by side.

AC motors on 1-phase power, there and here, use tricks for a "2nd phase" to get started and smooth the running. A 8uFd cap in each motor is cheap. (Before good caps, an extra coil on the frame, or hi-R winding, or a shorting ring.)

No, the real reason for 240V CT is we had a LOT of "100V" systems in place, and there was never a good time to rip it all out and go 240V. Much of Europe waited for better insulation before widespread electrification; and sadly War destroyed much existing electrics and post-War committees sought best-value systems, which would be 200-400V if you don't have legacy ~~100V systems.
« Last Edit: October 01, 2018, 09:32:35 PM by PRR »

Re: Two 110V devices on a 220V outlet
« Reply #35 on: October 03, 2018, 04:55:11 PM »
Thanks again Prr and John,

So first day on the shop floor today for me in the motor rewinds place , very good , fixed up a few multimeters that were troublesome, got a fluke ammeter clamp and another cheaper but well used meter going . Then I was allowed onto a job for a customer , some kind of of induction coils belong to the technical college ,mains powered , had a bridge rectifier with a bad solder joint on it ,they had assumed the coil was faulty . Two minute solder job and back up working ,so boss was impressed , he kinda said I fixed it too quick . I have the entire stock of  Farnell to pick parts for repairs from , really very little electronics at all though, Electromecanical for the most part , I was shown how to break down and extract the the coils on a motor and prep it for re-stuffing with new copper ,all the really dirty stuff is done in the oven room ,its like hell in there ,wire brushes&diesel , compressed air ,sharp cold chissels and ball peen hammers , gunky ovens that stink ,sh!t,muck and dust . A sample of the wires is always taken from the old motor , the insulation is blow torched off a section of wires ,then the gauge is cross checked . One of the coil sections is reserved for counting also .

I think  a serious look at the electrics to the benchs is in order  , They guys routinely use a 'suicide lead' to spark the windings on the motor for continuity ,its arranged with a light bulb in series and a couple of bars from electric heaters can also be switched in to drop volts . The  section with the bulb and load sharing resistors is seperate from  direct mains connection but still no iso transformer , which really would make a lot of sense here, probably a good plan is all the benches are fitted with Isolation transformers as soon as possible .and I said that to the boss . Theres just no need to be standing a the chance of full direct mains across your body ,even though the floor is well insulated , a ground lifted mains supply through a transformer would seem to be the correct way to do it ,even centre tapped to ground would be a big improvement , sometimes the windings of a motor short to case ,which could catch someone out easily ,with a floating mains supply only way you could concievable get shocked is by grabbing both live and neutral wires/terminals at the same time .

In the longer run its probably better for me to concentrate on the electronic side of things ,but Im being presented an oppertunity  to learn the trade of motor winding from the ground up while picking up technicians rates for any electronic stuff I do .

Star or delta configuartions depending on threephase or normal supply, the windings are divided into sections and loaded into the housing seperately , brazed together and insulated . The  windings are brought out to a six terminal block ,which can be configured for single or three phase . the more rpm the more sections to the coil . Loading the coils is preceeded by forming special paper insulators which are inserted into the coil slots first ,then after another folded V shaped paper strip in used to lock the copper into its slot and provide more insulation to case/ground. The sheer range of materials used is astonishing ,everything a transformer winder could desire ,big boxes of off cuts of everything .Some interesting caps ,high value motor start and runs ,40,50,60 ,70 ,80 uf ,250volts ac, crazy cheap as you said Prr, if size isnt an issue well capable of suplementing or replacing  electrolytics in tube designs.

Got asked by the boss for my bank account details ,and invited back down Friday ,so off to a good start .







JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #36 on: October 03, 2018, 05:39:58 PM »
Be careful working around mains voltage...

many technicians and engineers get too comfortable for their own good...

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Whoops

Re: Two 110V devices on a 220V outlet
« Reply #37 on: October 28, 2018, 08:33:46 PM »
Back in the day as a small manufacturer I could buy dual primary transformers that had two identical 115VAC windings. We could put them in series for 230VAC markets and in parallel for 115VAC market.

That's common practice at the present also

JohnRoberts

Re: Two 110V devices on a 220V outlet
« Reply #38 on: October 28, 2018, 11:37:23 PM »
At my last day job they were already staring to use universal switching supplies.

One sku could cover the entire world that way.

My current product uses AA batteries so no worries....

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.


 

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