Variable autotransformer

[CynicalMan]

I found this a while back in a pile of junk. It's a variable autotransformer. Any thoughts as to what I could use it for?

 

[kchriste]

Those are great for testing a piece of 120Vac powered equipment that smokes or blows fuses on application of power. Don't throw it away!

 

[stevez]

Some thoughts:
A. Use to slowly bring voltage up to older equipment to allow capacitors to reform.

B. With suitable isolation transformer you can build a variable AC or DC supply. Example: you use mains to 24 VAC transformer after the variable and you have a 0-24 VAC supply. Add rectifier and you have variable DC supply. You could also do this with higher voltage.

C. Use to test behavior of mains powered equipment at other than nominal line voltage.

One thing to note - this transformer may be an autotransformer and provide no isolation from the mains.

 

[Sceadwian]

It could be well used in a UPS box with my address on it =)
It looks like other autotransformers I've seen so as stevez said it's likely not isolated. Could be used to dim standard incandescent lightning. Keep in mind most auto transformers I've seen provide 0 to 110% of the input voltage so you can over voltage stuff if it's turned all the way up.
Try feeding it power from a 12 V AC wallwart if you want one and put a meter on the output to see if it still works, it looks to be in very nice shape.
My prefered use would be adding an issolation transformer some power diodes and beefy caps to turn it into a 0-120 volt DC power supply.

 

[crutschow]

You could actually use it to give both an AC variable output and a variable DC output. Wire it in a box with the AC output going to a standard wall jack. Also connect the AC out through a transformer of desired voltage rating with a diode bridge and capacitor filter to give a variable DC voltage. You could use a transformer with a center-tap output and a bridge rectifier to give a tracking (but unregulated of course) plus and minus dual output DC supply.

Just make sure to fuse the transformer output. The transformer rating is 2.25A so a conservative fuse value would be a 2A slo-blow.

 

[ecerfoglio]

Just make sure to fuse the transformer output.

The transformer rating is 2.25A so a conservative fuse value would be a 2A slo-blow.

Just make sure to fuse the transformer output as crutschow said.

A fuse in the input gives no protection (to the transformer) if you feed a short circuit (or overload) with a low voltage ratio

eg if you set the output at 6 V it can output 40A into a short circuit with only 2 A at its input, so a fuse at the input will not blow and the transformer may (will) be destroyed in a short time.

 

[CynicalMan]

Thanks, everyone!

The adjustable power supply is tempting but this thing is big. I might use it for testing equipment.

 

[Diver300]

Those are still made and they cost about $100.

SUPERIOR ELECTRIC|10C|VARIABLE TRANSFORMER | Farnell United Kingdom

Hang onto it.

It is not isolated. I've never seen a variac that is.

 

[dknguyen]

YOu can also use them as power supplies for foam cutters (used to cut foam wings for RC airplanes).

 

[tcmtech]

Hey! you took that from my shop! give it back!

Never mind. I still have one, two, five, 11! There mulitplying!

WOW! I should clean more often! Its like christmas but without the disapointment and anoying return process to get the cash I actualy asked for!

But really with a rectifier bridge they make super dc motor variable speed controlers!

 

[Sceadwian]

All you need to turn a big transformer into a big power supply, is a big capacitor =)
Think big! Even over rating to 3amps the diodes aren't gonna be a problem.

 

[arunb]

its known as a 'Variac', they could be used for testing electronic/electrical equipment. I use this all the time..