Hello,

I've asked about using US power tools in the UK before and the general feeling here was that it was OK.

I understand that the Uk site transformers supply 55 volts on both live and neutral but am I right in believing the US system is 120v live and 0v neutral?

Someone suggested that the saw would only be running at 2/3rds. efficiency and someone else said the motor would eventually be knackered.

So the question is would it be wise to get one of these - http://www.tlc-direct.co.uk/Main_In...110volt_Convertor_Transformer/index.html

Which one would I need for a saw rated at 13amps?

Thanks

David Lloyd

In UK (this is island specific, unknown on the continent, by the way) you use the two hot wires and no neutral, so you get 110 V to run your tools without too much danger.

In North America you got 110 - 120 Volts between one hot and neutral (there called grounded conductor).

The effect is the same, namely 110 Volts.
(55V is what you could feel when touching a hot wire in GB/IRL.)

The transformer in your link will need 230V input (+ island extra) to give 110 out, but watch the load limit, is probably not allowed on UK construction sites, and just would save the changing of the plug.

There might be differences with regard to devices with PE conductor as NA devices have a definite polarity (as English, but not European), but usually tools have double insulation anyway.

Wolfgang

[This message has been edited by Wolfgang (edited 11-14-2005).]

the highest rating I saw on that page was 3 amps.i probably wouldn't want anything over 2 amps running on that

The problems, even when you've got a piece of kit that works safely, within capacity, doesn't burn out your tools [i]and[/[] complies with the HSE site regulations on 110v, are:-
*HM Customs and Excise. Any imports valued at over about $20 will attract duty and VAT.
*Shipping charges, taking some of the gilt off the gingerbread. I recently tried to buy some specialist SOSS hinges from Wisconsin. The price was brilliant. But the co. wanted $120 ship + packing. No Deal. Got them from UK in the end, at double the price, not nickel plated as I wanted, but pack & post only $7.00.

Alan

Company policy seems to vary very widely on charges for overseas shipping. Some are very reasonable and charge only the actual cost plus maybe a couple of bucks for the extra customs forms etc. while others seem to want exorbitant amounts.


They go up to a 3kVA unit at the bottom of the page. The switch-on surge current would need to be taken into account on a 2 h.p. motor though.

The 110V CTE site transformers will work out a little cheaper. I can't see the split 2 x 55V supply being a problem in this application. (The older site xfmrs were accessible -- I have one about 35 years old to run some of my 120V gear in which I moved the ground from the center-tap to one end to provide "proper" 110V power. The new ones are all seem to be encapsulated in resin.)

I don't think you're going to find *any* US equipment with exposed metal surfaces that are wired to the neutral. European equipment (including all of that found in the uk produced in recent decades) is designed to be safe in either polarity. This is due to the fact that polarity is random in all 2-pin plug systems (ungrounded) and in Schuko system used in the majority of European countries for grounded appliances.

The plug system used in the UK and Ireland is always 3 pin (even for non grounded appliances) and the pins are arranged in a triangle so it only goes in one way giving you standard polarity on every appliance. However, with figure of 8 connectors and european plugs inside permanently fitted adaptor plugs in use in the UK and Ireland thesedays polarity's not always "correct".

As for your power tools. I would expect that they should be OK and quite safe on the centre tapped site transformers available for 110V 50Hz site powertools found in "these islands". You might get some weird performance problems associated with the frequency difference.

I would suggest that you remove the plugs and fit standard pin and sleeve yellow CEEform connectors (as these are standard for site work here)

Failing that, if it's for your workshop.. bring a few robust US trailing sockets (extension cords) suitable for the type of use that these tools get and fit CEEform plugs to the other end.

You will not find a single North American-market tool where this (55V to ground) will make a difference.

Historical curiosity:
I have an old book (House Wiring, by Thomas W. Poppe, 1930), which describes two ways of grounding a 120V appliance through the cord. The first way is pretty similar to the way we do it now. The second is by bonding the cord neutral to the appliance frame. A special polarized plug needed to be used, which was incompatible with the standard USA parallel-blade plug (now known as NEMA 1-15). This would have been a field modification and could not possibly have been very common. You wouldn't see it at all nowadays, since anyone ignorant and crazy enough to do this is also ignorant and crazy enough to omit grounds altogether.

Our equipment grounding (protective earthing) is exactly the same inside the appliance as yours is.

In fact, we have the same 60/120V center ground transformers here. They are a recent development, permitted by Article 647 for sensitive electronic equipment. This article originated in the 2002 NEC.

Sorry I did not expect to find an internal bonding to the frame in any modern appliance.
The only reason why I was hesitating about that issue is possible differences in capacitive bonding to ground against radio frequency disturbance. But this would only concern devices with a true ground (PE) conductor which are rare here as tools.

Good point. I've seen several references to this system with regard to audio studio equipment.

I've spent some time "overseas", and have dealt with this issue a little.

Many times, it will be possible to have your tools "re-wound" to fit the local system.

Probably a better arrangement is to a) rely upon cordless tools (buy new chargers) or b)get yourself a generator.
Another, more cumbersome arrangement is to take an inverter with you, and once there set up a car battery / charger / inverter to convert the local power to something similar to US power.

Erm... considering today's prices I'd say if you don't need very specialised tools or already own very expensive US tools it'd probably be cheapest just to buy new tools. Or go with the 55-0-55 transformers.

All my US tools - which I imported with me recently - are working just fine using a 3kVA site transformer. The only CEE 110V plugs connect with the transformer after which the whole system is NEMA 5-15. For historical reasons the 240V system utilises South African BS546 outlets and extensions where required. The workshop is quite cosmopolitan

Guys,

I'm confused :-)

I'm only a thick carpenter. :-)

Maybe I wasn't clear but I'm in the U.K. born here and lived here all my life.

I just happen to have an American wormdrive saw that I'm running off a 1.5kVa site transformer. The saw works fine but when I was speaking to an electrician at work about it he seemed to think it would maybe run a little better on a normal 120V Live 0V neutral.

We did talk about moving the centre tap towards the neutral in a site transformer.

So, the question is would it run any better. The sparky at work suggested that at the moment I'm only getting about 2/3rds efficiency.

Thanks

David Lloyd

Dave,
As long as you're happy with the performance with the saw ripping timber, and the motor isn't overheating, I'd carry on as before. I can't see a great difference possible between 50 vs 60 cycles in terms of cutting efficiency- I regularly put different blades between 250mm & 320mm diameter in my table saw, [which is a bigger change in peripheral cutting speed], with no problems or noticable differences. As to voltage, that affects the overall maximum power and thus speed of cut = feed rate. But a big improvement in electrical efficiency? I'll leave that to the 'electrical brains' on the forum, but I think that's unlikely, whether it's a brush or induction motor.

Alan

After all voltage is just a potential difference, and as long as the potential difference between the two wires is 120V everything should be ok. The different frequency might affect the magnetic characteristics as well as electrics a little, since inductance depends on the frequency, but that shouldn't be much, I assume that only becomes a problem with extreme low-end stuff with zero tolerances.
UK transformers don't supply a neutral, just two lives. Apart from the fact that there is a 180 degree phase angle (and not 120 deg) it's the same as with some older European systems that only brought 2 lives of a 127/220V system into the houses. Motors worked (and in some cases still work) quite happily on both systems.

I think Dave has happily been using his saw and will do so in future.

An asynchronous single-phase (capacitor) motor will run 20% faster on 60 Hz than on 50Hz. Its torque will be more or less equal. A lower voltage won't primarily affect torque, only current and possible overheating.

Voltage does not care at all whether it is leg-grounded, center-grounded or not grounded at all. (More a safety issue). American tools have to live with any voltages from 100V to 120 V as far as I know.

And single phase current will never care about phase angles, will it?

So what's the real problem, I ain't got it?


[This message has been edited by Wolfgang (edited 11-18-2005).]

The fact that the supply is a balanced 55-0-55 vs. 110V with one grounded conductor (neutral) is neither here nor there as far as the motor is concerned. It's still getting 110V with either system.

3-phase transformers can be found on building sites which give 63V from any phase to ground but still 110V between any two of the phases. As Wolfgang says, the 180 vs. 120 degree phase difference with respect to ground is of no consequence, since the motor is connected across two points only thus "sees" just a simple sinewave of 110V.

I can't see any way that changing from a center-tapped supply to one which is 110V with one conductor grounded is going to make any difference to the efficiency of the motor.

The frequency is more likely to have an effect, but I've never found this a problem on smaller motors under relatively light duty. I have an old 120V 60Hz Skilsaw which runs on 50Hz just fine, for example.

I suppose that a heavily loaded 110V site xfmr could result in the voltage dropping a little on the low side compared to the marginally higher nominal voltage of the typical U.S. supply, but it's probably not very likely unless the xfmr is really being run on the limit.

Thanks,

There's no real problem as such and as I said earlier the saw works fine.

It's just that the electrician on site suggested that it may run better with a proper US supply. I have nothing to compare the performance to so, I have no idea if he's right or wrong.

Thanks again

Dave

With the majority of power tools the difference in frequency would not present any problem as the motors on most tools are universal motors. Those types of motors will run off of 50Hz, 60Hz and even DC (although with DC many speed controls will not work, ON or OFF only) Large induction motors, as found on air compressors, may not like the frequency difference as much, but even in the case of induction motors, the lower voltage 110 vs. 120 will help offset the less than ideal reactance at 50Hz vs the 60 Hz they were designed for.

Personally Dave(Llyod),
I think the site electrician is just trying to confuse you.
If the saw has worked OK for the time that you've used it on site, stay with your current set-up.
As they say, if it ain't broke, don't fix it.

"As they say, if it ain't broke, don't fix it."


Words to live by

[This message has been edited by IanR (edited 11-19-2005).]

The point about universal series motors is a good one. In fact I was looking at Porter Cable routers a few weeks ago and the specs. on the website made a point of emphasizing that the tools are suitable for D.C. operation.

I'd go with the flow. I don't see any problem with your current setup.



[This message has been edited by pauluk (edited 11-19-2005).]

I went on a Ford Motor Co. Seminar on just this subject 15 years back. Ford Engineers had proved that 'planned maintenance' did more damage to machines by upsetting bearing-bedding, intoducing mis-alignment on reassembly and by the introduction of fresh crap to moving parts, than letting them run on. Not 'till they exploded from lack of care, of course! Their new method was called 'Condition Maintenance'; routine examination of lube quality, (ie metal content, additive breakdown, presence of contaminants etc.), checking the temperature of drives, bearings and slides with thermocouples, and analysis and comparison of vibration patterns from machines by microproceesors, all these would indicate when maintenance was actually required within close limits. Result: Better quality, less downtime, lower costs.
Lots of 'old-wives-tales' have a good core of common sense.
Needless to say, the Dinosaurs on our plant carried on taking everything to bits once a year regardless!

Alan

Re DC operation of appliances with universal motors, while the motors will be ok with it, the switches in modern appliances generally won't be. The gap between the contacts when the swtich is opened is likely to be insufficent to quench the arc.
Anyway it's more hypothetical than anything as DC mains no longer exist. There was however a commercially made gadget a few years ago which provided 240V DC from your car alternator. It was recommended for various heating appliances, power tools and incandescent lighting.
As the output from a car alternator is unfiltered rectified DC, any switch arc will be extinguished as per AC during the zero voltage part of the cycle.
I have never seen 50 vs 60 cycle operation of induction motors being a problem except for speed critical applications.

While it is unlikely that an occasionally-used motor will burn out if connected to the wrong frequency, one which runs continuously will not last long. I think this applies to induction motors only. Universal motors are safe.

Here is a better explanation than I could come up with.

I can recall connecting 50Hz induction motors in industrial situations here in the US. They always had transformers due to the difference in design voltage, but I wonder if the voltage was tweaked to compensate for the difference in current as well? That was so long ago I don't remember.

Has anybody ever monitored the output of a VFD with a voltmeter? Clearly an induction motor can be run at a variety of frequencies without harm, since VFDs are widely used.

That's the thing to watch. I assume that those Porter Cable tools specified for DC operation are fitted with the appropriate switches.


I think India is still supposed to have DC in some areas.


That's pretty much the way I would take it. Lightly used power tools etc. run on 50Hz aren't going to be a problem. I'd be wary of trying to run something like a refrigerator or air-con compressor on the wrong frequency.

I had seen reference to this in various tables of world electricity supplies up until the early 80's, but nowadays I'd be surprised if it does still exist, especially for domestic supply. I haven't seen any mention of DC rated domestic appliances for many years. Though given India's population it probably would be economical to still manufacture for a small market there.
In Sydney the last DC mains were killed off in 1985. It was a 480V centre tapped system feeding parts of the CBD mainly around the harbour. The +/- 240V supplies were used for lighting and appliances up until the 1950's but the 480V was still used for things like lift motors into the 1980's. By then the motor generator AC-DC converters had given way to mercury arc rectifiers.
Many country towns, particularly in Victoria and Western Australia also had DC supplies into the 50's. Interesting stories I've heard include when a light bulb filament went o/c whilst switched on....apparently the arc travelled up out of the light bulb, and up the flex to the ceiling rose. Then there was the electric jug with exposed element plugged into DC...the resulting boiled water had a strange taste with the electrolytic action that had occurred. And of course there's the usual burnt up power transformers when people took their mantel radios to these places and plugged them in.

DC supplies were still in use in some parts of Britain in the early 1960s, mostly the older parts of urban areas which had been the first to get electricity, so transformerless AC/DC radios and TVs were very common. Some models were made in an AC-only xfmr version as well though. I have an old Bush set which belonged to my grandparents and the service sheet refers to a field conversion kit which was sold.

I'm not sure of the exact date of the very last DC public supply here.

Vienna's last DC supply was shut down in 1955. A radio technician told me that DC used the same round pin plugs as AC, so correct polarity was not ensured. It was a 220/440V system.

That was the same here. If an AC/DC radio was plugged in the wrong way round, the dial would light up, as would the tube filaments, but there would be no B+ supply so it would remain silent. Some instruction booklets added a note to reverse the plug if this happened.

As the live would be positive with respect to ground/neutral in some houses, negative in others, when fitting a 3-pin plug to a radio it was sometimes necessary to deliberately reverse the connections from the usual. And of course, when taken to a house wired on the opposite pole of the supply, it wouldn't work again until the connections were swapped over!

An elderly gentlemen told me that they once had both AC and DC outlets in the same building, with no visible difference. Flourescent tubes accidentaly plugged into DC lit up in one end only and only once...

Oops... that's nice!
Vienna was converted from DC to AC around the 1950ies I think, most likely area by area. Some parts of Vienna already had AC power as early as 1903. The first district, i.e. the medieval inner city had both DC and AC, as well as the second district. All other districts had DC only, except for the 10. district which was AC only (mostly industry there). These districts already had 3ph AC available, I assume 127/220V.

I think I remember my brother telling me that the American expatriate Paul Bowles once attempted to make some ethnographic recordings somewhere in Africa (probably Morocco, since he lived there for many decades). After awhile trying to get the tape recorder to work, he (or one of his assistants) figured out that it was an AC-only machine, and the mains power was DC. Embarrassed and disappointed, he tried to explain the problem to his hosts.

They said something like, "That's OK, you can come back when the electricity is right." As if electricity were weather, and changed daily!

My dad bought a new Technics receiver in 1978. I remember reading the owner's manual (I was 10 at the time), and it warned explicitly against plugging the appliance into 120V DC supply. I was mystified as to where you might find this, but it went on to explain that some ships had DC circuits.

I remember reading a few years ago that 120VDC was very common on ships until the late '50s. The last of these ships would have been retired in the early '80s, so some of them would have still been around when I was reading this manual.

[This message has been edited by yaktx (edited 11-29-2005).]

[This message has been edited by yaktx (edited 11-29-2005).]

Like in 15 years when the area has been converted to AC!


Interesting on the DC supplies on board ships. I know some AC supplies on ships and aircraft are 400 Hz.

"I know some AC supplies on ships and aircraft are 400 Hz."

Thats because electromagnetic equipment (Xfrmrs and motors) are much smaller and lighter at 400Hz. Also for some of the Servos and gyros need really high speed motors to function. Synchronus speed at 400Hz is 24,000RPM versus 3000@50HZ or 3600@60Hz
But you knew that, right?



[This message has been edited by IanR (edited 12-01-2005).]

Plugging your 60 or 50 hertz alarm clock into one of those will REALLY make time fly.

I haven't heard of 400Hz being used on ships, but I believe it is used in aircraft because less iron is required in transformers and therefore less weight. It's interesting that some of the expensive US test instruments around here (eg; HP, Fluke, Tektronix) is rated for use on 400Hz mains.

I remember some years ago seeing one of the brochures for either a cross-Channel or North Sea ferry which made a point of warning people that the outlets on board supplied 220V at 400Hz.

I think that 400Hz on ships is more a military thing than on civilian vessels.
Most US Naval ships and Subs have two to three electrical systems; a high voltage DC system, 60Hz general distribution and 400Hz for the radar and missile guidance systems.
As for Aussie240's comment on test equipment.
That is probably due to the fact that the military is a very high paying customer.
I work at a military contractor and we don't think twice about droping a quarter of a million on a 100GHz spectrum analyzer or 100K on a digital O-scope. Heck, as I type this I am looking at a cabinet containing about 2 million worth of test equipment. And my lab is one of the smaller ones on campus!
We have several that are much larger.

[This message has been edited by IanR (edited 12-02-2005).]