Switching AC voltage real time

[hsdhilon]

Hi,
Is there any device which I can use to increase or decrease input volatege to some device. I need to test a computer system (basically the power supply installed in it) to see how it behaves when I increase the voltage from 110V to 150V or anything upto 230V.
I googled on the net but couldn't find any such device so I thought may be experts on this forum can help me out. Any help or pointers are really appreciated.

Thanks,
Harp Dhillon

 

[itsmoked]

hsdhilon,

You need a variable transformer. Often called a variac.
They are sold at a lot of places.. Most are 0-130V or 0-150V. Less common are ones that go higher. I included a site here that makes units that go to 280VAC with a 120V input.

http://www.iseincstore.com

This was the first google site in the list so there are a lot of choices.

You probably want one that is enclosed. These things are heavy, ~20 pounds, but fragile, and they have live parts all over them so an enclosure is important. Check that the current your to-be-tested supply requires can be supplied by the choosen transformer.

I would expect most PC power supply's will do a major smoke job if you boost them past 130VAC.

 

[sreid]

Perhaps the fastest way to buy a Variac is to is to order one from McMasters

http://www.mcmaster.com

 

[SolderingGunslinger]

I agree with itsmoked (it smoked because it wasn't brought up slowly with a variac ;-) )

A Variac is a very useful thing to have in the shop/laboratory. Trouble-shooting power supplies becomes much easier with a variac.

Good Luck.

I remain,

The Old Soldering Gunslinger

 

[ruggedscot]

Wow a variac and switching between 110 and 240 carefull !

some power units are designed to be operated from both voltages but they are not designed to go between those voltages - can cause damage if ran at 110 and then ramped up to 240. ensure that they can and then if in doubt dont as those electrolytic caps do have a nasy habit of popping when you least expect it.

 

[OperaHouse]

I have a variac that I run into a 120 to 240 auto transformer. They sell these for bench testing 240V equipment. Just make sure you have a high enough current variac because at 60V out to the transformer, you will draw twice as much current. A lot of power supplies are auto between 90 and 265 volts.

 

[ScottyUK]

There are number of manufacturers of solid-state power sources for this sort of application. More expensive than a variac, but much more flexible in what it can do. Try

http://www.calinst.com/acpower.html

for a start.



----------------------------------

If we learn from our mistakes,
I'm getting a great education!

 

[leonar40]

Check out Staco for some nice Variacs. They even have digital ones now.

http://www.variac.com

 

[walker1]

Yes a lot of off-line SMPS can work from 90 or 100 VAC to 240VAC or more.
However I have not yet seen any in a standard PC. One of the high-end brands maybe and most notebooks.
For desktops not the ones we mere mortals have the budget to buy.

 

[VEBill]

There was an 'unreliable' PC here that would only work in certain locations. Turns out its PS was accidently set to 240v input. It actually worked (!) in certain outlets (at 120v).

 

[wrong100]

If you are doing a static test,(will it work)
than a variac is fine.
Note the normal (no mans land and turn it off
for the transition, if you must).
If you "must have the voltages within a given range"
for the transistion time you need something
to switch between the voltages.
About 4 or 5 major companies make them.
I do not know public, but Mil spec is 10us for the transition and (pub lightning spec). You must understand that all input as well as output caps must be charged in this time = same as startup (output for overshoot volts (value greater then prior voltage)). I would suggest an inital current source ratio of between 4 and 10 to 1.
Example just went round and round on a simple supply.
Numbers said .05 sec., scope said .3 sec,
source was limiting the start time, (changed from 5 amp limit to 50 amp, problem solved).
Cost is about,10 to 15 percent, of a new item for a rental.
I hope this helps.