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AC Voltage stabiliser

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Tarzan

New Member
Hi, An AC Voltage stabiliser (130 and 230V) is a handy tool.
But I searched the net and couldn't find a serious paper describing a possible circuit.
Can anybody assist in bringing up some ideas to get it starting?
Zerro crossing switching, voltage adjustment from 240 to 220V, Amps up to 6 Amps?
Thanks, Tarzan
 

Sebi

Active Member
The older version work with transductor and autotransformer. I don't think nowadays need some equipment this.
What is Your application?
 

Tarzan

New Member
It must stabilize the Mains to an exact 220V. Input can go as high as 250VAC.
It must do the job without human intervention.
It must be small, light and not expensive.
A Triac can do the job, but here I must say I miss the knowledge to do it properly.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
As Sebi asked, what's the application?.

It's very unusual for anything remotely modern to require a specifically accurate mains supply. As Sebi also mentioned, you used to be able to get 'voltage stabilising transformers', I don't know if you still can?.
 

Styx

Active Member
as mentioned above...

but IF and only IF you really need exactly 220V (reasoning please). then the only way to do it will be an active solution.

use a step-up trasformer to get say 250V (for 220V AC) this is for some voltage headroom

Rectify and then use a PWM inverter to generate a stable 220V AC
 

Tarzan

New Member
I have a bunch of valve equipped measuring instruments.
They are in excelent, if not mint condition and I like to keep them that way.
But the AC voltage went up from 220 to 240VAC.
Thats 9% up. The Heater Voltage as the High Voltages are higher then when the equipment has been designed.
To stabilize the voltages or to keep them at 220V (and subsequent secondairy voltages) I need a Solid State solution. No Variac or other magnetic stuff.
I do have other friends with valve amplifiers and they have the same problems and like to have a small unit (me to) that can be build in to their gear.
So a Variac or other bulky solutions (they work, we all know) is out of the question.
Any hint to a possible solution is welcome.
Thanks for the response so far.
Tarzan
 

Styx

Active Member
are you sure it went up to 240V !!!
europe use to work on 220V and UK worked on 240V

To make inter-operation work UK came down to 230V and Europe went up to 230V.

This increase/decrease in voltage is way within the normal voltage tolerance of all things that were attached to the utility.
 

Tarzan

New Member
I live next to a distribution transformer. So voltages are average 240V.
My question whas if someone can help me to find a solid state solution to reduce the 240VAC voltage to a stable 220VAC.
It has to be small, cheap, solid state.
It is to be placed BEFORE the original power transformer in equipment and testinstruments.
It is needed to work with or use equipment fed with the AC voltages they have been designed years and years ago.
It's not because the elctricity companies are raising their line voltage I have to buy new equipment.
I believe that such a device can offer a solution to my problem (and many others)
Tarzan
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Tarzan said:
I live next to a distribution transformer. So voltages are average 240V.
My question whas if someone can help me to find a solid state solution to reduce the 240VAC voltage to a stable 220VAC.
It has to be small, cheap, solid state.
It's not going to happen!.

The way to do it is an auto-transformer, it meets none of your criteria, but is the only solution without having a specific load in mind.

It is to be placed BEFORE the original power transformer in equipment and testinstruments.
It is needed to work with or use equipment fed with the AC voltages they have been designed years and years ago.
I don't see why you would want to?, 220V equipment is perfectly happy on 230V mains - in the past much 220V equipment was used on the UK's 240V mains without problems.

If your mains is excessively high, you should complain and get it changed, but what are you using to measure it anyway?.

It's not because the elctricity companies are raising their line voltage I have to buy new equipment.
I believe that such a device can offer a solution to my problem (and many others)
Tarzan
I've never heard of any problems with the mains change?.
 

panic mode

Well-Known Member
just get 220/18V transformer with secondary current rated higher than what you need and wire it as autotransformer... (maybe you can canibalize car battery charger, they are inexpencive).
Since this will work on 240 (9% increase) the output will be a tiny bit
higher (approx 1.8V) making it almost 20V (18+1.8=19.8).
If you wire it correctly, you can use this to reduce your line voltage by
the same amount making 240-19.8=220.2V
I'm kidding with decimal points just to give you idea. If your equipment
is so precious and delicate, run it on few volts lover (how about 210-215?).
On the other hand if it's really so sensitive, why consider dirt cheap solutions?
Real DIY guy would ripp it appart, throw out the prehistoric power supply
and replace it with something more modern and stable like switching power supply. Leave valves for the audio circuits only and add alot el wire.
now that's a mod your girlfriend will fall for... :roll:
 

Tarzan

New Member
Well as far I can read, nobody seems to understand the problem.
All I want is some sort of idea or information on how to make sure that equipment being designed for 220VAC is getting 220VAC even if the offered mains can climb up to 240VAC.
As it has to build in to these equipments all the proposed solutions are not applicable.
I appreciate all your time in writing to this forum but wished that the main question would be clear and some one could jump on the idea of a small unit that is to be build into the equipment, is cheap and solid state.
AT the moment the idea of using variac, transformer or SMPSU is the big idea by most of the writers.
It's to big, to expensive and to costly. Non of these comply to the question.
Thank you any way.
Cheers,
Tarzan
 

Styx

Active Member
Tarzan said:
Well as far I can read, nobody seems to understand the problem.
All I want is some sort of idea or information on how to make sure that equipment being designed for 220VAC is getting 220VAC even if the offered mains can climb up to 240VAC.
As it has to build in to these equipments all the proposed solutions are not applicable.
I appreciate all your time in writing to this forum but wished that the main question would be clear and some one could jump on the idea of a small unit that is to be build into the equipment, is cheap and solid state.
AT the moment the idea of using variac, transformer or SMPSU is the big idea by most of the writers.
It's to big, to expensive and to costly. Non of these comply to the question.
Thank you any way.
Cheers,
Tarzan
dear god!!!! you ask for help and then get smarmy. If you think we dont "understand" the problem, it is because YOU have not describe it in enough detail!!!!

quite a few peiople have said that something designed to run at 240V will run fine at 220 and also things at 220 will run at 240V - it was this tolerance of voltage that allowed mainland Europe and the UK to harmonise their utility supply.

And before you ask I kno how to generate it! I even stated what you have to do!!! IF it really is nessecry - just read the posts here before you kick off with the free advice you are getting!!!!!!!!!
 

Tarzan

New Member
Well to finish the tread:
Do you know how much the live of a valve is shorted if the heaters get 8V instead of the 6.3V?
If you can say "It stays the same" well BIG mistake.
Can you be sure, ABSOLUTELY sure that the HV caps will witstand the minimum 10% higher voltages without exploding?
Are you willing to pay to rewind all the transformers (not 1 but 26...)with odd secundaries so that they can witstand 240V?
Can you design a SMPSU tha is able to provide some equipment with 12 different voltages and delivering some AC voltages for monitor purposes?
Can you make sure that with the use of a Variac the mains voltage stays stable even if some or more equipments are switched of?
I don't think you can.
Therefore a seperate unit that reduces the 240VAC to 220VAC and that can be build in to each equipment is needed.
What more can I say?
And that's jsut one part of the problem...
 

Styx

Active Member
dear god you are a bit of a jack-ass arnt you...

as I have said use a PWM inverter. Rectify the AC to provide you with a DC. This DC will vary as the "supply varies"

By using a PWM inverter (switching-frew of say 10kHz) and using a closed voltage loop to ensure that the voltage stays at that level.


one problem with that is you have stated the suppy will goto 240V but not what it will go downto. you need a bit of voltage overhead since you will loose 2V in the rectifer and another 2V in the inverter stage
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Tarzan said:
Well to finish the tread:
Do you know how much the live of a valve is shorted if the heaters get 8V instead of the 6.3V?
If you can say "It stays the same" well BIG mistake.
Can you be sure, ABSOLUTELY sure that the HV caps will witstand the minimum 10% higher voltages without exploding?
Are you willing to pay to rewind all the transformers (not 1 but 26...)with odd secundaries so that they can witstand 240V?
Can you design a SMPSU tha is able to provide some equipment with 12 different voltages and delivering some AC voltages for monitor purposes?
Can you make sure that with the use of a Variac the mains voltage stays stable even if some or more equipments are switched of?
I don't think you can.
Therefore a seperate unit that reduces the 240VAC to 220VAC and that can be build in to each equipment is needed.
What more can I say?
And that's jsut one part of the problem...
I can't make sure the sun doesn't go supernova tomorrow, but I don't worry about that either!.

European imports into the UK commonly (always?) were rated at 220V, back when the UK mains supply was 240V. As someone who has been professionally employed repairing electronics for over 33 years the only one of your concerns that has any truth in it is that 220V equipment had a slightly higher incidence of mains transformer failure than 240V equipment. Although this could well have been down to the particular make of transformers used, certainly the ones which failed never seemed to look particularly well made - and most never failed!.

Anything with a switchmode supply should be perfectly OK, these are normally self regulating, and 240V will be well within their specifications.

If you want to be particularly paranoid about it, fit auto-transformers to any piece of equipment that you think warrants it - but they are not cheap, small, or light weight.
 

zevon8

New Member
I have only ever had to do what you want to do once. This was for a piece of automated test equipment used in a factory producing flourescent lamp ballasts. Fairly tight AC line regulation was required so that the test results were consistant, and only reflected variations in manufacturing, not the line voltage.

The solution was to use a ferroresonant power conditioner. This, like mentioned above, is a big auto transformer circuit. It by no means fits ANY of your criteria though...

- Very large
- Very expensive
- Most certainly NOT light.

As a possibiltiy, you can sometime find these iron giants at surplus dealers. Their day in the sun is long over, and the ones that haven't made it to the scrap metal bin, often can be had at reasonable prices.
Sola is one company that makes a nice unit ( they still do actually. )
 

Sebi

Active Member
Anyway the 240V only almost 10% overvoltage for older devices, don't worry about tube heating, this is only about 6,85V! This is better for older tubes, and the datasheets also enable it. (one of 1000 wrong tube have heater failure!)
Not impossible to reduce the effective voltage with triac, but this method make a waweform distortion, generate BIG noises, and need hard filter circuits. The filters also contains iron cores and X2 type capacitors (not small). The "light" solution is a seriel connected 24V bulb with appropriate W.
 

pebe

Member
Tarzan, I see you point, especially about valve heaters. Regarding the comments about 220v supplies being OK on 240V, I wouldn't agree that would always be possible. When I was working (now retired) we used professional equipment of Belgian manufacture and rated for a 220V supply, on 240V. After the first three transformers gave up the ghost we measured primary current at 240V and found about a 50% increase over the current when supplied from 220V through a Variac. The primary turns or the stack size was obviously marginal.

I also bought a Panasonic cordless telephone while I was on the continent. That was rated 220V and power supply suffered the same fate.

But there is a fairly simple solution which is neither bulky nor expensive. Get a 240V to 20V transformer and wire its output in series with the 240V mains so its voltage bucks the mains. Your old pieces of equipment can then all be fed from a common 220V supply.
 

Tarzan

New Member
Hi Pebe,
I'll try it out but at the same time I'll look for a smaller solution that can be build in to the equipment.
Most equipments do have the room to harbour an extra transformer as you proposed but musical instrument amplifiers are mostly full, apart from the combos.
Thanks for the tip.
 
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