Basic isolation transformer

Thread Starter

ApacheKid

Joined Jan 12, 2015
418
I want a transformer that accepts 120v and generates either 120v or 240v on the secondary, supporting say a 2 KW load.

Where can I find such devices?

Thx
 

crutschow

Joined Mar 14, 2008
27,734
Have you searched the standard transformer suppliers?

That's a large transformer and will be expensive.
It will also require a 20A, 120V outlet.

What's your budget?
 

Thread Starter

ApacheKid

Joined Jan 12, 2015
418
I've not searched any suppliers, I wasn't sure how to search for a transformer with two separated 120v secondaries that I can then switch together as desired. The power is just a random guess, its for general workshop use.

Perhaps a smaller one is fine, most stuff will be low power, old radios and so on, its likely rare to never that I';d need KW type stuff.

Of course getting 240v 50Hz would be nice, but that's a different problem altogethe!
 

MrChips

Joined Oct 2, 2009
24,207
Don't try to cover all possibilities with one solution.
Since high power transformers are expensive, satisfy your immediate power requirements first.
 

Ian0

Joined Aug 7, 2020
3,245
Cost varies with power.
However don't forget the possibility of "intermittent" ratings. You can get 3x the power out of a transformer that way, but not for long.
 

Thread Starter

ApacheKid

Joined Jan 12, 2015
418
If you are in N.A. why the need for 50Hz?
What is wrong with the 120v 240v supply? or is this not a residence?
Nothing big but I just might have some old TV or something one day that needs 50 Hz, this is not a real need though, I was just remarking that I'd need more than a transformer for this.
 

crutschow

Joined Mar 14, 2008
27,734
No matter what you are working on, always plug everything into a GFCI socket.
That will protect you from any fault between the mains Hot and ground.
 

dendad

Joined Feb 20, 2016
3,910
For most applications, 60Hz will work just as well as 50Hz, unless there is a synchronous motor involved with critical speed needs, like a record player or clock.
And 50Hz transformers can give a bit more power out when running on 60Hz.
I have seen once, a 60Hz transformer that overheated when run on 50Hz so going that way can cause problems.
If you are just wanting this for "home" electronics, 100 or 200W will be plenty. Have a look on the back of the devices you want to play with for their power requirements.
2KW or more if you want to run a heater, but as pointed out above, it will be expensive.

One way to go is run a couple of transformers back to back. So, for example, a 120V to 24V, then connect the 24V to the second transformer's 24V, and you end up with another 120V.
This will give you an isolated 120V and that is very useful for some tesing.
But, if you want, one end of the second 120V winding can be connected to the end of the mains 120V in phase so it will add, giving you 240V.
BUT, you will no longer have isolation.
Please be careful.
 

Thread Starter

ApacheKid

Joined Jan 12, 2015
418
50Hz may be the least of the problems if relates to a TV, NTSC - PAL etc.
Plus, signals are now digital.
Yes that's likely true, the 50 Hz isn't a big deal. I do recall that I found a guy on youtube once who was clearly a skilled electronics designer.

He built a system that could take an HDMI signal and convert it into an NTSC/PAL (or it might have just been a monochrome 405 or 625 line signal, can't recall) signal that could be fed right into an older TV set, the video showed it running.

I'll try to find that again, but last time I looked I couldn't.
 

crutschow

Joined Mar 14, 2008
27,734
He built a system that could take an HDMI signal and convert it into an NTSC/PAL (or it might have just been a monochrome 405 or 625 line signal, can't recall) signal that could be fed right into an older TV set, the video showed it running.
Many set-top boxes were sold to convert over-the-air ATSC signals to NTSC during the changeover, such as this.
 
Top