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Eli’s a long-time friend of Toolmonger, and comments pretty regularly hereabouts.  He’s moving to Austrailia soon, and finds himself in a bit of a fix regarding all his beloved power tools, both corded and cordless.

He writes: “Since RIDGID doesn’t make an Oz voltage charger, I’ve checked the Australian site of a certain online bidding service and come to the realization that tools are really pricey there.  It might make sense after all to bring ALL of my tools with me when we move there, even with the hassle of having to use special converters. I’m pretty sure they are 240 volts @ 50 cycles, and we are 120 volts @ 60 cycles.”

“So I’ve been looking at step down transformers, and working out all the wattage of my tools.  I thought maybe there was an electrical engineer or Australian ‘Monger among us that could help me determine safe working loads for the different stuff.  For example, my Makita power planer is 4 amps, which as I understand it translates to about 440 watts (amps x current=watts).  But I’m wondering how high a wattage transformer I should have for safety under load.  A grinder or any saw or a thickness planer would all be different under load.  I don’t mind buying several and hard mounting them right to the tool itself for the big ones, and keeping it with a U.S. extension cord in a bucket or something for the hand tools.”

We’ve contacted some of the manufacturers to see about conversion kits with no luck, but we wondered if some of you might have ideas for alternate solutions to the problem.  To help out, we’ll kick out a Black & Decker AutoWrench to a single commenter of Eli’s selection in this comment thread.  (And if you don’t care about the AutoWrench, we’d appreciate it if you’d offer your wisdom anyway.  Remember, we Toolmongers have to take care of our own!)


13 Responses to Reader Question: Step Down Transformers to Charge Tools on Aussie Power?

  1. Michael says:

    Eli, check out voltageconverters.com
    ( http://www.voltageconverters.com/voltage_converters.html ). Obviously tou’ll want the higher wattage units for your power tools. Hope that helps.

  2. Christian says:

    Disclaimer and disclosure: I am an electrical engineer, NOT an electrician, but I know somewhat more than enough to be dangerous in that capacity. I also spent some time doing theatrical lighting tech and electrician work, up to the 500KW total load level. Talk to an electrician before doing anything suggested below – this is not professional advice by any means!

    With that out of the way, take a look at industrial solutions like McMaster’s 7029K46. This is a 3000 VA (volt-amps, what motor-driven tools are actually rated at, which is somwhat different than watts for reasons that are not really germane here; it has to do with Power Factor – make sure you look at the VA (NOT watts!) rating of things for your shop) 240-120V industrial transformer. It’s about 300US$. This should run anything on 120V in your shop – 3000VA will handle anything that a normal US 120V 20A circuit breaker can do.

    Maybe wire up your shop with regular US outlets for your tools (and 240V outlets for lights, radios, and other locally-sourced 240V loads), and run a permenant circuit into this thing? Probably safer and certianly more convenient than switching extension cords. And remember that power strips tend to not be rated for things like stationary power tools!

    They also have 5000VA units for a little more, if you’d like to run multiple tools, and small ones if I’ve misunderstood your needs, and you don’t want to run things 12″ arm saws and 13″ planers.

    But for this sort of heavy-duty use, I’d avoid the little consumer-grade things. These are likely not meant for serious, long-term use with inductive loads like power tools.

    Whatever you do, it’d pay to speak to an AUS electrician for a little bit – I’d suspect that they might have some experience with this, and can tell you about AUS electrical codes for 120V appliances or wiring.

    Ahh, I’ve been assuming that you know about McMaster-Carr (mcmaster.com), supplier of all things… well, actually, just plain all things! I went there and searched for “Step-Down AC to AC Transformers” and found lots of good stuff, especially on page 889.

  3. I concur with the above advice to buy a big serious heavy expensive awkward frequency-converting step-down device, not just a cheap autotransformer. Inductive loads, like motors, typically run hotter when you try to run them from mains power with a lower frequency, which is what you’ll be doing if you use simple step-down transformers.

    Step-downs are fine for many small devices, and for anything driven by a switchmode power supply (which cares not about input frequency, and which is likely to be world-compatible anyway), though.

    Given the how expensive the serious converters are, how much power they eat all by themselves, the expense of shipping large tools from country to country, and the fact that your tools do not appear to be big pricey three-phase devices, I think you’ll probably do better to sell your tools in the States and buy new ones once you get here.

  4. Christian says:

    The 50Hz/60Hz situation is tricky to evaluate. If your load is an induction motor that is open-frame, or has a low duty cycle, or has some sort of exteral cooling, or otherwise does not generate very much heat, then you are probably OK. It _will_ run slower, which is OK except that the motor will not cool itself as well. This may not be a problem. I have a lathe with a TEFC (totally enclosed fan-cooled motor, handy for not getting coolant and oil into it) that has an external fan on it to cool the case (which is itself a heat-sink). I’d have to modify this and add extra cooling capacity if I tried to run it on 50Hz – it would likely overheat with extended use.

    If you have a universal motor’d device, like most circular saws, Dremel-type devices, and smaller bench power tools, you may also be OK. These will run on anything down to DC without noticing.

    And, by the way, you know those homebrew rotary phase converters (not the static ones – I mean the kind with two motors hooked up back-to-back) for making 3-phase in your home? You can do a similar thing with a 240V 50Hz motor and a 120V 60Hz motor. There _will_ be a little ‘frequency loss’ (that will vary with load) due to the fundamental nature of induction motors, but with sufficient oversizing of the motors (vs. the load) you’re OK.

    But I agree with the above poster. This is all pretty big and heavy stuff, for running _more_ big heavy stuff. Maybe you want to only bring the smaller cordless tools and your father’s heirloom B&D drill (the yellowish one) and run them off a solid-state voltage/freq converter (a bigg computer UPS, the kind that takes 240V in, might work too).

    Check the nameplates on your chargers – you might find that some are already good for 90-250V, 48-62Hz. Some manufacturers find it easier to make and stock one power supply for the whole world, and just change line cords – and you can get the adapters needed with no trouble.

  5. nrChris says:

    If you are going to move long-term you may be better off switching set ups entirely. I know selling used tools is not a good perspective, but at some point you are going to want to be able to do any work anywhere without worrying about how to charge your system. Just my $0.02.

  6. Evan N. says:

    Hope I’m not being redundant, but here are some useful formulas —

    Power = Current x Voltage. So the number of watts (power) used by your tools will be the same in Oz and the US — just that with higher voltage, less current is drawn. This is why even in the US some tools are 240 V tools — so that if they draw 20 amps at 240 V it would be like 40 amps at 120 V. It’s more efficient to run tools at a higher voltage sometimes because the heat buildup in the wiring (like when you run a full 20 amps through an extension cord it gets hot) goes with the square of the current, so (40 amps)^2 = 1600 but (20 amps)^2=400. So a double in current actually makes 4 times the heat. (The formula is actually (heat)=[(Current)^2]x(resistance) but you get the idea).

    I really don’t know about the consequence of line frequency difference. The good news seems to be that for a motor at a certain power (say 1/3 HP) it will draw half as much current at 240 V than at 120 V.

  7. Christian says:

    Of course, the motor must be designed to run at a given voltage. It would be…unwise… to run a 120V motor at 240V.

    On the other hand, some industrial motors can be rewired (by the user) to run at 120V or 240V – my lathe’s TEFC 1/2HP motor works this way, and can also be rewired to run in either direction. There are about 12 wires in its built-in junction box that are connected in various combinations to line & neutral to acocmpish these things.

    But that’s US 240V (60Hz), not AUS 240V (50Hz).

  8. ambush27 says:

    I don’t think you need anything very powerful to run your tools off of, as far as the 120 volt tools go because the 120 volt tools can’t draw more than 1800/2400 watts each anyway. but if you’re going to run a table saw or a large compressor or any other 240 volt tool you’re going to need something a good deal more powerful. assuming you decide you have to compensate for the frequency difference.

  9. Me says:

    I am not an electrician or electrical engineer. I spend some time hanging out on the rec.woodworking newsgroup. (I use Google Groups to read it.) I know there are several Aussies that also hang out there. They might have some good info on your situation. There are a lot of helpful people there. Just a thought.

  10. Eli says:

    Thanks for all the input. I’m still not sure, but I’m definitely closer to making a decision.
    These guys:
    made it seem like if I took the wattage (of the tool) and got a transformer for 50 percent greater coverage, to account for surge, I should be alright.

    It’s hard weighing the hassle of selling the stuff and buying it anew against the hassle of using something unfit for it’s environment. The other thing to take into account is that my tools might take two months longer to get there than I do. I don’t think I’ll be able to not work, even if it isn’t for profit. My work papers will take a while and my mother in law has just purchased a flat with plenty of hobby projects. That will mean that whether the American tools go or not, I’ll likely have bought new tools by the time they arrive. Chuck, maybe it’s time to provide a place on TM to buy and sell user tools? I hate yard sales, they’re so undignified.

  11. Chris Ball says:

    1.5 more ways to approach the problem are to pick up a generator and just use that for power, this has a couple advantages, you get to avoid any potential frequency issues and you won’t need an electrician to do anything for you in the new shop. If your needs include big stationary tools, miller makes a bobcat model for about 3k that provides three phase power and throws in a tig welder for free, which is probably what I should have done for my shop as the costs between the new panels and wiring past bobcat money a while back and I still don’t have a tig.

    The other 0.5 is mostly addressed by someone else above, you could pick up a generator head and just drive it with any old locally sourced electric motor and bob’s your uncle.

  12. SlowJoeCrow says:

    Depending on what you are going to be doing you may have 120V power available. In the UK construction sites often use 110V power to reduce shock hazards, and the rental shops stock heavy duty transformers to allow using industrial tools on 220V house current. I can’t say what they do in Oz, but they often follow UK practice.

  13. Some 120v american appliances with transformers can be re wound to 240 volt or some times they are just wired from one pole too two pole and run it at 240

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