Question on 240V AC Mains step up supply for US Mains

[markmalin]

Hi all,


I'm building an amp for use in Europe.  I've sourced the proper Power Transformer and wanted to get a step-up transformer/supply that I can plug into my US mains (115-120V/60Hz) and test the amp at 240V/50 or 60 hz.  Wondering if anyone has a suggestion for a supply for my shop?  I see lots of them on Amazon, etc.  Would sure appreciate recommendations.

Thanks
Mark

[sluckey]

That seems like an expensive way to get 240VAC. You already have 240VAC in your house. I suggest to just use an existing 240 outlet (install one if need be). Build an adapter cable with the correct male plug for your home outlet on one end and the correct euro style female plug on the other end.

[markmalin]

That seems like an expensive way to get 240VAC. You already have 240VAC in your house. I suggest to just use an existing 240 outlet (install one if need be). Build an adapter cable with the correct male plug for your home outlet on one end and the correct euro style female plug on the other end.

Well...that would certainly do the trick :)

[pdf64]

If you do get a step up transformer, verify the ground connection.
It may be 3 pin, but on many, especially cheapo units, the ground doesn’t pass through.

[shooter]

if you have an electric dryer, oven, or hot water tank, those are good spot to tap some 240 juice.  just be REAL cautious 240 bites hard

[pdf64]

Pfff, it’s not proper 240V, only 120V to earth, and a friendly 60Hz 

We keep the good stuff over here 

[tubeswell]

If you're building for 240VAC 50Hz, just remember that the PT iron needs to be bigger than you would use for 220VAC 60Hz (because of the higher power and inductance of the 240V mains - the area under the function curve is the total power). If you undersize the PT, it will run hot and won't last.

[markmalin]

If you're building for 240VAC 50Hz, just remember that the PT iron needs to be bigger than you would use for 220VAC 60Hz (because of the higher power and inductance of the 240V mains - the area under the function curve is the total power). If you undersize the PT, it will run hot and won't last.

Ok, so my question is this.  Say I build a standard AB763 circuit with a given Hammond power transformer model spec'd at 120V primary and it works great - and Hammond sells the identical model transformer, but a 240V version.  If I use the 240V version of the same transformer, you're saying that's not sufficient for my power transformer?


Trying to understand your comment.  :)


Mark

[tubeswell]

If you're building for 240VAC 50Hz, just remember that the PT iron needs to be bigger than you would use for 220VAC 60Hz (because of the higher power and inductance of the 240V mains - the area under the function curve is the total power). If you undersize the PT, it will run hot and won't last.

Ok, so my question is this.  Say I build a standard AB763 circuit with a given Hammond power transformer model spec'd at 120V primary and it works great - and Hammond sells the identical model transformer, but a 240V version.  If I use the 240V version of the same transformer, you're saying that's not sufficient for my power transformer?


Trying to understand your comment.  :)


Mark

If the physical size of the 240V PT is about at least 1.2x the size of the equivalent 120V PT it should be okay. If there is not enough iron, then the inductance at 240V/50Hz will kill the PT after a few hours.


This problem is usually taken into account by good PT manufacturers. (But its nevertheless something to be aware of if you're making amps for euro mains)

[markmalin]

So even if it's spec'd by Hammond as a 240V version of the same 120V transformer I would normally use, if it's not physically 1.2 times larger, I should not use it, even though Hammond says it's the 240V version?? 

[sluckey]

I would not be concerned. Hammond's export transformers are rated for 50/60Hz. I trust they know what they're doing.

[tubeswell]

So even if it's spec'd by Hammond as a 240V version of the same 120V transformer I would normally use, if it's not physically 1.2 times larger, I should not use it, even though Hammond says it's the 240V version??

Some PT manufacturers will make a product based on the minimum amount of cost materials needed to do the job for their largest number of customers. Others will tend to spec the product for maximum durability/versatility.   '1.2 X' is my rule of thumb for this (having seen a few compact looking stateside-made PTs burn out on mass-produced amps shipped here, and then having to have locally made ones manufactured to replace these and having had several discussions with local manufacturers here over the years about this. It has been quite a common thing in the past). 1.1 would be okay. I have some champ-spec Hammond PTs in my stash and they are small, and they do run warmish on 50Hz. For a 20W+ amp, I'd want the PT iron to be bigger - just saying

[sluckey]

I believe Hammond knows that. Look at these two examples...

     https://www.hammfg.com/files/parts/pdf/290EX.pdf

     https://www.hammfg.com/files/parts/pdf/290EEX.pdf   (export version)