Variac 20A AC Power Auto Transformer What can you it for examples

[sam_sam_sam]

I just bought myself this Variac transformer I changed the very crude volt meter that it had inside it

I would like to know what type of uses this unit could be used for

One Would like to do is make DC power supply to try out out LED modules

Awhile back I came across a LED module that ran off 48 volts and did not have a power supply that would do 48 volts so I had to buy a 50 volt 5 amp power supply with I seen to use quite often but it was a little pricey

I do not want to have to buy a different power supply for testing a LED module only find out that the LED module is bad

This brings to a question

I would like to use a bridge rectifier with a capacitor and fuse

400 volt 2 amp bridge rectifier
with a 2 amp breaker
What microfarad capacitor should I use at what voltage

To have a dc power supply

What else should I use,do to make this setup as safe as possible

One note

With the control knob turn all the way to the right the voltage is 151 volts AC


One other question I have is what other uses does a Variac have please give examples

[petehall347]

Re: Variac 20A AC Power Auto Transformer What can you it for examples

use for bringing power up slowly on older electronics without switching circuits .. they are not always good for this . like valve rectifiers as they wont conduct until high voltage thats one to be aware of but still useful .
the other is jfet audio amplifiers in particular that will self destruct being brought up on a variac .
i mainly use mine to trim the voltage up a few volts as i have low voltage issue here . i only use for servicing amplifiers though .

[llonen]

Re: Variac 20A AC Power Auto Transformer What can you it for examples

As above mainly I use these for slowly powering up some of the vintage refurbishment and repairs that come though the workshop, older electronics not so good on switching supplies. I also put together a rectifier and smoothing pack for this which I use for reforming vintage capacitors.

I can look into the values if you need when I am next in the workshop.

[sam_sam_sam]

Re: Variac 20A AC Power Auto Transformer What can you it for examples

As above mainly I use these for slowly powering up some of the vintage refurbishment and repairs that come though the workshop, older electronics not so good on switching supplies. I also put together a rectifier and smoothing pack for this which I use for reforming vintage capacitors.

I can look into the values if you need when I am next in the workshop.

If you do not mind could you please provide this information

Thanks

[stj]

Re: Variac 20A AC Power Auto Transformer What can you it for examples

use it for questioning people.

[lax luthier]

Re: Variac 20A AC Power Auto Transformer What can you it for examples

That is a BIG variac. Few things you should be aware of. Don't mess with the substance that may be used between the windings and brush.

You cannot accurately check them using an ohmmeter. The brush design is such that it needs a certain amount of current through it to conduct properly. If you are going to test one, power an incandescent lamp or power resistor that won't exceed the max current rating (not so much a problem on yours but there are lots of smaller types in the field). Evaluate smooth continuous output by measuring the voltage across the load.

Most intermittent issues on old units are caused by corrosion in the slip ring not the brush-winding contact.

Fusing needs to be on output, due to power dissipation conditions. Primary fusing is optional.

They are very versatile and useful equipment.

Many techs recommend having an isolation transformer to follow a variac, for good reason such as if you are using it to power equipment you're poking around in, just good electrical common sense.

The types that can output higher than the line in voltage are useful to make up for voltage drop in branch circuits so that equipment testing can be done at the line voltage specified in the DUT's service manual.

There is a service available that will re-tip your brush at a fraction of the cost of new one.

They are fun to use

Regards, -L L-