I think if you just look at them as a variable mains supply that idea may help.
Don't connect anything to it that you would not just plug into the wall socket. .

AFAIK this was the original intention, in order to use equipment that did not conform to a certain power/socket voltage. Or experiment with such sealed/insulated equipment.
Not to feed bare circuitry.
Max.

 

One of the advantages of using an isolation transformer is to remove the connection to the ground. I'm assuming in the USA it is the same as here in Oz that the neutral of the mains (240V here) is connected to ground at the house switchboard. Then the circuit being worked on can be probed with an oscilloscope. Also, if you then touch part of the circuit while holding anything that is grounded, ( test equipment ground or workbench.... ) there is a lot less risk of getting plated.
I vote for isolation transformers and use one when needed. Yes, high volts are still there but it does make servicing easier and safer.

 

And Ron, that describes me exactly. So, I am staying away from them for now.

Good move and someday as you learn, the Variac or Auto-Transformer will be your new best friend.

My point was that in the wrong or better put untrained hands there is no shortage of things which we can label dangerous. Beyond the auto-transformer things like high explosives come to mind. However, to call something out as dangerous simply because in unskilled hands it can be dangerous is a little over the line in my humble little opinion.


Ron

 

Hi,

Yeah variacs are used in kitchens around the USA and other places for slow cooking purposes. There is one particular thing they use them for in the kitchen but i cant remember what it was now. I didnt now this until about a year or two ago when i read about it. So some people even not related to electronic work know how to use them properly, which is good to hear.

And yes, the variac is made with a single winding which makes it cheaper. It is just a primary winding with a tap on it, while most other transformers are made with two windings where the second winding does not touch the first winding so there's no direct electrical connection.

They do make variacs that are isolated but as others have noted they are more expensive. The variacs i have now and the ones i had in the past were not isolated because i did not really need that, i just needed to have a variable mains voltage.

Back in the 1980's we had variacs that were four feet high and you could never lift one. They were three phase with ratings up in the 10's of killowatts. They did 240vac also. They had to be on wheels.

 

Back in the 1980's we had variacs that were four feet high and you could never lift one. They were three phase with ratings up in the 10's of killowatts. They did 240vac also. They had to be on wheels.

Used them in a few large, very large power supplies all run on 480 VAC three phase and motor driven. You didn't just pick them up and move them.

Ron

 

Used them in a few large, very large power supplies all run on 480 VAC three phase and motor driven. You didn't just pick them up and move them.

Ron

Hi,

Oh yeah that's right, we had a motor driven one too back then. One of the tech's in the shop turned it all the way up before testing a high power converter thinking it was being turned all the way down. When turning on the breaker, the large (8 inch high by 3 inch diameter) electrolytic caps exploded like dynamite. Bent the 1/4 inch thick copper buss bars up on a 90 degree angle

Thinking back like this, "I seen some stuff"