Isolation transformer question

Other than small efficiency issues I can't think of any.

1.0KVA means the _maximum_ primary current times the _maximum_ primary voltage equals 1KVA. To get 1KVA at 115V from your 1:2 transformer, you'll run things at half the rated voltage and twice the rated current.

IF you're running no more than 400KVA or so then it's probably no problem. If I really felt I needed to I might try it up to 600KVA or so, but only if I monitored the temperature of the bits to make sure that nothing's getting too hot.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com 

I'm looking for work -- see my website!

KVA.

ed 230v.

ed only

the

** Yes - you can get double power from the 115:115 one.

The 115V tranny is rated at 8.7 amps output while the 230V one is rated at half that.

The current rating does NOT go up at reduced input voltage.

.... Phil

Except making more heat and burning up the wiper. Ever have a variac apart ? Once I saw the build it was "I am not using that thing unless I really need to".

Hmmm, I wonder now, are those things supposed to be cleaned every once in a while like guns n shit ?

The output impedance will be much lower if the variac is near 100% and the transformer doesn't step up.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

On 19 Jul 2016, snipped-for-privacy@gmail.com wrote (in article):

I did clean both brush tracks. (Many don?t realize that theres two brushes: one rides on the coil; the other connects the ?disc? that holds the main brush to the connector terminals.) Much better continuity linearity with those tracks cleaned.

How would this display in everyday use? More output current? Or...?

Maybe more current, but certainly less voltage droop with increasing load current. If you are willing to crank the variac to tune the voltage under load, that may not matter.

Variacs have least loss, and lowest impedance, near 100% output voltage.

If you use a 2:1 step-up transformer to make 120 volts at 1 amp, the variac has to drive the primary at 60 volts and 2 amps.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I had a lovely variac (really more like a "Staco Energy") fire. Evercise those wipers by turning the knob from time to time, as they're sort of self cleaning, but even that's not enough some times like in my case.

I smelled something awful, entered the room full of horrible phenolic smoke and saw the thing on fire. Half flames, half glowing wire and brush assembly.

Now that someone had boiled this thread back to the top I see you f***ed up there buddy. That would be 1:2 not 2:1.

I am sure you know that and I am not accusing you of stupidity, it is just one of those errors. And there is no edit button. I thought a correction wa s warranted.

Anyway, if possible the variac should run off the transformer, not the othe r way around. In fact I would consider using the 1:1 in series with a varia c to get to 220 provided you don't really need the isolation and you don't have to go below 110.

I am pretty damn good at working on hot stuff. Walk into wirk ad work on a hot chassis TV all wet from the rain outside and on a cement floor. It take s some care, and knowing, and you can't expect everyone to understand it we ll enough and think it out well enough to be safe working on hot. In fact e lectricians who can do it are highly sought.

So err on the side of safety and don't zap yourself. (not you, you're proba bly alright when it comes to this shit) But people need to be able to ident ify the parts of what they take apart. See that AC cord ? Where the wires f rom it goes is the dangerous part when it comes to a grounding issue. And w hen you see those big fat wires that feel all rubbery, that is high voltage . Also, if it has any tubes in it, just keep one hand in your pocket, and e ven that doesn't work. Last year I made a mistake, basically because I hadn 't worked on tube equipment for so long. Even the one hand thing didn't wor k, it just burned a hole in my one hand.

You can work without isolation, but IIRC OSHA requires the area to be cordo ned off and danger signs planted around it. That because there are times in industrial settings where you have no choice. They also still sell wood la dders...

There is alot of equipment to which this doesn't apply - but the dim bulb t ester is more useful for some things. Like audio amps and TVs for example.