Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Transformer alternatives

Status
Not open for further replies.

Frosty_47

New Member
Hello, I would like to know what alternatives there are to the use of step down transformer. Say, I needed to transform 120VAC to 24VAC and I have very high current requirement (30Amps as an example). The use of such transformer will be highly expensive + the overall weight and size of such transformer would be 2 impractical. What alternatives are there?

Thanks
 
Not many really...much else would be more expensive and lower capacity...but possibly lighter or smaller like a large boost converter. Though the size of the inductor might be very large anyways.
 
Last edited:
If you don't need isolation between the 120vac and the 24vac you might consider an autotransformer. They are smaller and cheaper since they only have one winding (hence the lack of isolation). The voltage is tapped off the winding, sort of like a potentiometer.

Fixed autotransformers are not common but a transformer manufacturer may have them or can build one for you if you have the budget. A common variable autotransformer is a Variac.
 
One thing that I've done in the past was to use a 480/120 power step down transformer. Yes it's still bulky/heavy, but I needed a high current low voltage source like you. With 120v on the primary (480 terminals)you should get about 30v on the secondary...I don't know what the voltages are in your area, so this may not be possible...
 
Smps

You need to look at a switch mode power supply, although these will be very expensive, in larger sizes.

I fitted a 750 watts 240 / 24 Volts SMPS yesterday in one of our substations to support the scada system.
That one is rated at 30 Amps. load was around 25 Amps initially, then tapered off to a steady load of 15 Amps.
 
RODALCO said:
You need to look at a switch mode power supply, although these will be very expensive, in larger sizes.

I fitted a 750 watts 240 / 24 Volts SMPS yesterday in one of our substations to support the scada system.
That one is rated at 30 Amps. load was around 25 Amps initially, then tapered off to a steady load of 15 Amps.

Except he specified needing 24v AC, not aware of any SMPS that provides 60/50 Hz AC output ;)

I can't think of an effcient method of generating 23vac at 30 amps that would not involve a transformer either in it's input stage or output stage if an invertor is tried.

Lefty
 
If here were a cheaper alternate to a transformer for converting AC voltages, the power companies would be using it.
 
There must be some kind of educational deficiency out there because this question keeps coming up and the answer is almost always the same.
 
Thank you all for your suggestions

I agree with PapaBravo on "Education Deficiency" as really none of my professors or any electrical people I know seem to have an answer for this. I tried studying switching PSU's however; I found no mention of this topic. Switch mode are basically more efficient but they still require a stable DC input voltage in order to work thus the need for transformer again.

What about Computer PSU's ? Mine is ratted for almost 80A combined and hell, there are no bulky transformers inside of it. Just a few bifilar chokes, inductors, and one very weird, multi-winding, tiny transformer that I would give no more than 1A ratting...

Any more ideas any one? I am seriously fed up with google giving me bunch of useless crap that’s non-related to the desired topic...

Thanks
 
crutschow said:
If you don't need isolation between the 120vac and the 24vac you might consider an autotransformer. They are smaller and cheaper since they only have one winding (hence the lack of isolation). The voltage is tapped off the winding, sort of like a potentiometer.

Fixed autotransformers are not common but a transformer manufacturer may have them or can build one for you if you have the budget. A common variable autotransformer is a Variac.

Thank you for that info, I think electrosonic has some variac's. I will definatly do more search on that....
 
and one very weird, multi-winding, tiny transformer that I would give no more than 1A ratting..
At the high frequencies that they use, these 'tiny' transformers may provide 500W++ at any voltage that they are designed for.
 
Like look at this S41t ! This is the kind of garbage I get when I type in "Transformer Alternatives" in google. Here is the very first result:

http://thetransformer.us/

These morons don't even know what a transformer is yet they name their site with it. Wish those people who registered the above domain, get hooked up to the secondary of a microvave oven transformer
for a period T -->
 
Last edited:
mneary said:
At the high frequencies that they use, these 'tiny' transformers may provide 500W++ at any voltage that they are designed for.

500Watts for that transformer ? WOW! But how do they step up or generate high frequency without stepping voltage down in the first place ? And even if they do use HV components, wouldn't they require a DC source to operate ? and those timers or w/e they using to generate High Frequency be limmitted to very little current ?

Sorry, I am not trying to go down hard on you, I just realy whish to know more... If you know any good articles, can you please provide a link...

Thanks
 
500Watts for that transformer ? WOW! But how do they step up or generate high frequency without stepping voltage down in the first place ? And even if they do use HV components, wouldn't they require a DC source to operate ? and those timers or w/e they using to generate High Frequency be limmitted to very little current ?

Sorry, I am not trying to go down hard on you, I just realy whish to know more... If you know any good articles, can you please provide a link...

Search for 'switch more power supply'.

Essentially they rectify and smooth the mains, giving 320V DC in the UK, in the USA they usually use a voltage doubler to give a similar DC voltage. This voltage is then chopped at a high frequency (between roughly 15KHz to 100KHz) and fed to a very small transformer, the output of the transformer is rectified and smoothed, where you can use MUCH smaller capacitors because of the higher frequency. The output voltage is monitored, and correction signals sent back to the chopper to alter it's mark/space ratio and keep the output constant.

Incidently, the worlds first domestic use of a SMPSU was in the Thorn 3000 colour TV about 1972 or so?.
 
500Watts for that transformer ? WOW! But how do they step up or generate high frequency without stepping voltage down in the first place ? And even if they do use HV components, wouldn't they require a DC source to operate ? and those timers or w/e they using to generate High Frequency be limmitted to very little current ?

Sorry, I am not trying to go down hard on you, I just realy whish to know more... If you know any good articles, can you please provide a link...

Thanks


The physical size of a transformer is governed by its losses, not the power that is "transformed" from input to output. Losses typically consist of resistive, eddy current & core (magnetic). Controlling these in your design will determine your maximum power rating.



A typical "offline" switchmode converter will first rectify and smooth the line thus creating a high voltage DC. From there, a PWM method is used on a flyback transformer to generate the right output (typically)
 
Incidently, the worlds first domestic use of a SMPSU was in the Thorn 3000 colour TV about 1972 or so?.

I remember the 3000 chassis. Now with a fond recollection, but at the time I hated it. More than 80% of the faults were P.S.U. faults, not so bad when you had your list of stock faults. (On paper or in your head no computers as such then).

Rick Br@nchTV.
 
I remember the 3000 chassis. Now with a fond recollection, but at the time I hated it. More than 80% of the faults were P.S.U. faults, not so bad when you had your list of stock faults. (On paper or in your head no computers as such then).

I loved it back then as well, I built a jig for repairing 3000 panels, and one for repairing Bush A823 panels as well - I've no idea how many panels I repaired over the years, but it was a LOT! :D
 
The physical size of a transformer is governed by its losses, not the power that is "transformed" from input to output. Losses typically consist of resistive, eddy current & core (magnetic). Controlling these in your design will determine your maximum power rating.
Which is a nice theory. In practice, resistance and core losses go up as dimensions go down. And like every good law, there is an exception: At very high frequencies the resistance goes up again due to the skin effect.
A typical "offline" switchmode converter will first rectify and smooth the line thus creating a high voltage DC. From there, a PWM method is used on a flyback transformer to generate the right output (typically)
Flybacks are normally not used at high power. The reason is that you can get twice as much power through a core in a bridge topology.

The https://www.electro-tech-online.com/custompdfs/2008/05/e22616.pdf can run around 100W flyback or 200W push-pull, and the https://www.electro-tech-online.com/custompdfs/2008/05/e641050.pdf can pass 3KW!
 
Smps

Sorry for my earlier reply, I must have been tired, and thought you needed a high current DC supply.

I didn't read your question correctly and missed that you were after a high current AC supply.

As already said by our other members, an autotransformer is lightest but the output is not galvanically separated from the mains supply.

Regards, Raymond
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top