Variac voltage transformer question

[yhprum]

A general question about Variac transformers.
Here in Australia mostly all household wiring is 240 volts. I have a number of US voltage power tools and I have been using step down transformer that by itself has been working fine.
I also have Harbor Freight electronic router speed control I use in conjunction with the transformer sometimes.
While it does work ok, it seems a little messy of a way to do it. I feel it could work better.
I also dont have a 240 volt router speed control, which I would like to have.
So I was thinking perhaps if I got a 240 volt Variac transformer maybe I could use this for all my variable speed and transformer needs for my US and Australian power tools. I’m unsure if a Variac will affect amperage the same as a step down transformer would.
Am I totally off base with this idea? Thanks for your inputs!

 

[walta]

Most Variac do not allow enough current flow to operate most tools. Read your labels my guess is the tool could pull 4-8 Amps and the Variac is limited to 1.5 Amps unless it is huge.

Does your router have built in variable speed or a soft start as many larger and new router do?

If so, be very careful about what electricity you feed it.

For any tool with a simple on off switch and brushes in the motor the Harbor Freight control is fine but motors without brushes will not be happy.

Also make sure any old (pre 1975) tool with a metal case has a 3 prong cord that is properly grounded as your life may depend on it.

As a general rule the step down transformer used to run a tool must weigh more than the tool or it is likely putting out less than the 120V the tool needs.

Walta

 

[dave*99]

My 10 amp Staco variac is about the size of my Porter Cable 691 router. The router draws about 6 amps.
I’ve never plugged the router into it.

 

[dogdog]

I don’t think a 240vac router speed controller will work well with your 120vac router or any 120vac motor tools. Usually the tool is design to run on 120-ish volt and it is brushed ac or brushed universal motor. The 240vac speed controller is nothing but a fancy dimmer that clips the voltage either on leading edge of trailing edge of the wave form. So at 240vac the max is still 240vac if no step down transformer is used. …. Unless you also changed out to a 240vac ,corded tool.


It’s not like the cordless that their charger will work with 90vac up to 240vac. Stuff like that

 

[yhprum]

All my tools are single speed variety, no variable speed.
The Variac I had in mind was the old school type that has a barrel shaped body and a large knob on top that you turn to change the voltage and is fairly heavy for its size. I had an old 110v one years ago that I let go.
So I think you’re saying that with this style Variac the ampere capacity remains relatively constant irregardless of the voltage output?
I like that rule of thumb about the sizing of the unit. Thanks

 

[dogdog]

maybe just a plain step up-down transformer ? Get reputable brand one , not just by COO.. some sketchy one I got that is cheap smells scary. 5000VA could run almost all hand tools you have.. well... but they are heavy also.

I have good luck with this brand at least their ultrasonic cleaner so far. But not much else... I think they are like the Canada-ian Harbor freight I think.. but at least the item is a bit less sketchy than Ebay unknown brands. Still COO China.

VEVOR Step Up and Down Transformer – 5000W, 5V USB Port

Looking to power devices globally? VEVOR 5000W step up and down transformer safely converts 110V/220V with USB ports and quiet operation. Order yours today!

www.vevor.com

Side question: why wouldn't you just get the hand tools from the country you lived in and leave those in the US.. ? don't even know how you get those hand tools pass customs these days.

 

[Norcal]

The reason people buy US 120V tools is price, in the UK they use a "site transformer" that steps 240V to 110V, each leg is 55V, since it's 50 Hz, & the 120V tools are 60 Hz, the 110V output is ideal for the volts/ hertz ratio.

 

[minke]

A variac is an autotransformer. See: https://en.wikipedia.org/wiki/Autotransformer

If the variac can supply enough power then all is well. Is your power 50 or 60 Hz? It may matter and I don't know enough to help.

 

[yhprum]

maybe just a plain step up-down transformer ? Get reputable brand one , not just by COO.. some sketchy one I got that is cheap smells scary. 5000VA could run almost all hand tools you have.. well... but they are heavy also.

I have good luck with this brand at least their ultrasonic cleaner so far. But not much else... I think they are like the Canada-ian Harbor freight I think.. but at least the item is a bit less sketchy than Ebay unknown brands. Still COO China.

VEVOR Step Up and Down Transformer – 5000W, 5V USB Port

Looking to power devices globally? VEVOR 5000W step up and down transformer safely converts 110V/220V with USB ports and quiet operation. Order yours today!

www.vevor.com

Side question: why wouldn't you just get the hand tools from the country you lived in and leave those in the US.. ? don't even know how you get those hand tools pass customs these days.

 

[yhprum]

Dog dog, Some were tools I brought with me from the US, and some others were not available here at 240 volts.cheers

 

[75gmck25]

I have an old 120 volt, 10 amp Staco Variac that I pickup up off eBay, and based on the web site below they still sell a lot of similar products. I used mine to feed variable voltage to an old tube radio I was rebuilding, since I wanted to test replacement vacuum tubes before running them at full voltage.

I'm guessing these Staco units are too expensive for home use if you have to buy new, but someone out there on eBay might be selling a 240 volt version that meets your needs. The used items I found seemed to mostly come from sales of old university lab equipment. I also found quite a few newer models being sold, and they all seemed to use a standard design. Not sure of their quality.

VARIAC 240VAC Input, 0-280VAC Output

 

[wmesquite]

I have a 240 volt 5 amp Powerstat variac I bought as New Old Stock on ebay for $26 around 2005, maybe 5" diameter 6 inch high. You'd probably have to pay more now. But there is one thing to note- for a high quality variac like this, it deals with overloads pretty well- The 5A rating is the limit for 500 hours of continuous on time. It is rated for 10 amps continuous for 20 minutes- as long as you are under 50 C degrees. And 25 amps for up to a minute. So it should deal fine with short term overloads from starting a tool. I’ve used mine to reform capacitors on older VFDs up to 10 hp, so some fair sized short term current peaks.

As stated before electronic controls associated with the tools such as soft start may not tolerate reducing voltage very far from their native voltage. But with a quality variac you should be fine otherwise. Always better if you can get a manual showing the current/ time overload curve for your chosen model. I don't think the Chinese ones would allow for much of one.
Wade

 

[RPH]

I have a bunch of variacs from the older surgical lights. They do become handy in the shop. Also a bunch of 35 vac power supplies for another surgical light system. One thing you learn quickly is this stuff is heavy duty power supplies.

 

[humber2]

I’m late to the party, your safety is totally dependant on the neutral connection staying intact otherwise wherever the knob points will be line input voltage out.

There is no harm using an earth leakage breaker, i’d consider it essential.

For power tools you will need at least a 5 amp unit.

YMMV