Transforming 220V to 110V

[TellyS]

I have asked many people this, but never got a straight answer. Perhaps someone in this forum can shed some light.

I have several calculators that are designed to operate on 110V. In Europe, I need to purchase a transformer to convert the 220V to 110V for proper operation. The question is how big (in Watts) of a transformer do I need? For example, if my device draws, say 0.5A at 110V, do I need a 55W transformer (110*0.5) or a 110W (220*0.5) ?

I thought I understood this by saying that the transformer needs to "handle 0.5 A regardless of voltage, so it should be 110 W. But then I looked at the back of my HP 9815A and I see that at 220V it draws 400mA, but at 120 V, 725mA. Does that mean that the calculator draws half the current at about double the voltage?

Your help would be appreciated.
Telly S

[Maximilian Hohmann]

Hello!

(11-11-2024 01:31 PM)TellyS Wrote:  Does that mean that the calculator draws half the current at about double the voltage?

Yes: P = U * I
(P:power U:voltage I:current)

This is the reason why we have higher voltage in Europe. It keeps the current lower and with it the losses in the cables.

Regards
Max

[TellyS]

(11-11-2024 01:37 PM)Maximilian Hohmann Wrote:  Hello!

(11-11-2024 01:31 PM)TellyS Wrote:  Does that mean that the calculator draws half the current at about double the voltage?

This is the reason why we have higher voltage in Europe. It keeps the current lower and with it the losses in the cables.

Regards
Max

Thank you for clarifying this for me, Max.

[AnnoyedOne]

250V in Western Australia (and the UK?). 240V is the rest. 220V is most of the EU. 110/120V in North America. Then there are different plugs/sockets

Most stuff uses switching PSU's which can handle all. However small things often still use an AC/DC adapter so you have to have the right one for your country.

Fun isn't it

A1

[TellyS]

(11-11-2024 01:45 PM)AnnoyedOne Wrote:  Fun isn't it

A1

Very much so.
I have a Brother label printer which is the only one that does not have a switching power supply. One would have thought that the power requirement is rather low and, hence, doable.

Telly

[emefff]

Hello,

you just found out why 110V for single phase in the US wasn't a very good choice to begin with (high currents need thick wires and lines etc.)

I doubt it is a real problem, but you wouldn't find 220V anywhere in Europe because all countries switched to 230V more than 25-30 years ago (one exception, I think is Georgia, but I am not sure). Real single phase voltages can be as high as 240V though.

(11-11-2024 01:45 PM)AnnoyedOne Wrote:  220V is most of the EU.

NO!

Having been a DIY tube electronics builder a long time ago, I even bought a 230 to 220V transformer back then, because all of the vintage tube stuff works on 220V. I think they are still available, but I don't know for sure.

Also, you should NOT max out the max. power of such a transformer or power supply, whether it is a classical transformer with windings or a switching power supply. Stay away from the max. at least 50%, because PSU tend to degrade over time,

emefff

[AnnoyedOne]

(11-11-2024 01:52 PM)emefff Wrote:  ...but you wouldn't find 220V anywhere in Europe cause all countries switched to 230V more than 25-30 years ago...

I stand corrected.

FYI with a lot of AC powered stuff it is common to use VA (volt-amps) vs W (Watts) because many loads are inductive (or even capacitive). Thus PF (power factor). Most things try and keep the PF around 1 (resistive) to keep power companies happy. As I recall most transformer based PSUs have a PF of around 0.8. Not an issue for small loads.

A1

PS: Then we could get into the whole 50Hz/60Hz thing.

[TellyS]

(11-11-2024 01:52 PM)emefff Wrote:  I doubt it is a real problem, but you wouldn't find 220V anywhere in Europe because all countries switched to 230V more than 25-30 years ago.

NO!

Having been a DIY tube electronics builder a long time ago, I even bought a 230 to 220V transformer back then, because all of the vintage tube stuff works on 220V. I think they are still available, but I don't know for sure.
emefff
[/quote]

You are right. 230V in Greece (at least that's what my UPS reports). Since you brought up the issues with older calculators, I have a nixie ELKA calculator that requires 220V. I have been running it on a transformer 110V->220V in the US, but have not plugged it in at 220V/230V. You think that 230V would be an issue? I do have a 240V->220V converter...

Telly

[AnnoyedOne]

(11-11-2024 02:50 PM)TellyS Wrote:  You think that 230V would be an issue? I do have a 240V->220V converter...

230V is only about 4.5% above 220V so personally I wouldn't worry about it.

A1

[emefff]

Well, how much do you love your old electronics? The older stuff tends to be more at its limit than new electronics, because of dried transformers, capacitors etc. The Nixies are tubes, so also their heating and other voltages are raised. I doubt they have much of a self-correction in their schematics, do they have a soft-start for the heating? Tube heating wires tend to, just like incandescent lamps, fail during power-on because they are PTC resistors, so currents can be very high during a cold-start. In the tube days a soft-start was a must for longevity of the tubes.
If you want to risk it, fine. But I wont tell you that it's without risk, because, as I said, real voltages can be even higher. Maybe it's fine once or twice or ten times, but perhaps not for years of usage.
I found the old 230 to 220V transformer, yay. I could plug in the 1959 Philips Philetta and listen to some radio, if it still works, that is.

emefff.

[TellyS]

Well, I am not going to do my taxes on a nixie tube calculator, but I would like to turn it on occasionally.

I bought this from Amazon some time back.

500W Voltage Transformer Converter

Inputs are: 110V, 200V, 220V, 240V and outputs: 110V and 220V. Seems to be working well.

[HPing]

A youtuber makes fun videos testing consumer power supplies. He has a slight Czech accent and a cat. And serious engineering chops.

He makes a good pitch to stay with branded power supplies from trusted suppliers. He seems to rate most of the unbranded stuff as "Dodgy" for fire risk, electrocution risk, and/or good power delivery.

I can't remember if he "reviewed" these types of line transformers.

https://www.youtube.com/@DiodeGoneWild

[John Keith]

(11-11-2024 02:30 PM)AnnoyedOne Wrote:  PS: Then we could get into the whole 50Hz/60Hz thing.

That can be an issue for transformer-type power supplies. Transformers made for 60 Hz run hotter when run on the same voltage at 50 Hz. Usually not a serious problem but worth looking out for.

[Maximilian Hohmann]

Hello!

(11-11-2024 10:13 PM)John Keith Wrote:  That can be an issue for transformer-type power supplies.

And anything with an AC motor inside. Like electromechanical calculating machines, (computer) tape drives, mechanical clocks (but also vintage electronic clocks that are synchronised to the mains frequency), some record players, telescope drives, etc. Even fans can make strange noises when operated with the wrong AC frequency.

When we were visiting the computer museum during our forum meeting in Stuttgart two weeks ago, the curator told us that they have a lot of work converting machines that are made for 60Hz to properly run with 50Hz.

Regards
Max

[TellyS]

I am told that there is a transformer that converts frequency as well as voltage. Would that be a huge one?

[John Keith]

(11-12-2024 07:46 AM)TellyS Wrote:  I am told that there is a transformer that converts frequency as well as voltage. Would that be a huge one?

That would be a VFD, essentially a switching power supply that rectifies the incoming power and converts it to AC at the desired frequency.

[AnnoyedOne]

In addition to the above electrical issues 50Hz/60Hz can also affect product functionality.

Years ago, before more sophisticated SoC's became available it wasn't uncommon to use the AC line frequency for timing functions. I did it. Not an issue unless the product is used in a place where it was never intended to be. For example a relative once bought a digital clock, on sale, at a retail store and I noticed that it wasn't keeping the correct time. After some simple math it was evident that it expected 60Hz Ac vs 50Hz. The product was returned.

These days most SoC's have multiple timer/counters etc so as long as the parts operating frequency is known (typically requiring a crystal) one can implement accurate timing.

Some of my digital clocks do this even though the AC frequency where I live is pretty accurate (power companies are often required to do that). It is pretty easy to figure out from any "drift" over a few days.

A transformer based power supply output DC output voltage can also change with frequency. Usually regulated but again heat issues can result.

The point is that any given product may be designed for one, the other, or less commonly both. I've written firmware that auto-detected and acted accordingly. Also fixed (assumed).

The EU is all 50Hz to my knowledge. North America is 60Hz. So even if you get the voltage right other issues may arise.

A1

[John Keith]

(11-12-2024 01:01 PM)AnnoyedOne Wrote:  The EU is all 50Hz to my knowledge. North America is 60Hz. So even if you get the voltage right other issues may arise.

Amazingly, some parts of Japan are 50 Hz. and some are 60 Hz. IIRC, this was a big problem after the Fukushima disaster as it prevented the sharing of power between regions.

[AnnoyedOne]

(11-12-2024 05:21 PM)John Keith Wrote:  ...this was a big problem after the Fukushima disaster....

Hmm, is the heat due to power incompatibility or radiation?

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