Hello,

I have a couple of American power tools that I am running off the standard 110 volt / 50 hz site supply in the U.K. and want to know if I am doing any harm.

I looked at the plates on some of my U.K. tools and it says 110 volt / 50 - 60 Hz.

One American tool says 120 volt 50 - 60 Hz.

The other American tool says just 120 volt 60 Hz.

As I understand it the frequency affects the speed of a motor so how can a tool be rated at either 50 or 60 Hz?

Am I wrong in thinking that the 10 volts difference is not a real problem?

Thanks

David Lloyd

There are synchronous and asynchronous motors. A synchronous motor's speed will be affected by the frequency. An asynchrous one won't care too much. And most tools have asynchronous motors. The 10V difference won't do much harm I think. After all some stuff works on a low 220V system as well as on a British 240V...

Thanks,

Is there a way to determine which type of motor a tools has?

I see long leads all over building sites so I imagine no tool gets the full 110 volts anyway due to voltage drop.

I imagine the best thing for me to do is keep he leads as short as possible and use as heavier guage as possible, or am I just being too cautious?

David Lloyd

It shouldn't be a huge problem 110V 60Hz is well within the tollerance of any US product. The old official rating was 110V and I'm sure that there are plenty of outlets in the US and Canada that supply closer to 110V than 120V.

If the frequency isn't an issue it work just fine.

The only thing to note is that the transformers used in the UK and Ireland provide 2 X 55V lives out of phase. So, you've 110V between the two lives and 55V between either terminal and ground. This reduces the potential for electric shock.

It's really not a problem, however just be aware that your powertool could be live with 55V even when the switch is in the off position.

djk,

The one tool in question is marked 120 volts 60 Hz.

How do I determine if the frequency is an issue or not?

I'm confused about the tool being live with 55 volts with the switch even in the off position. I didn't get a shock, burn, or tingling sensation yet :-)

David Lloyd

[This message has been edited by davelloyd (edited 11-14-2004).]

 
Most US motorized power tools have universal motors with a wound armature. Those should run OK, but maybe at a little lower speed from 10 volts under [and not 10 Hertz under.]

120V resistive heating devices at 110 V would dissipate 84% (110/120)² of nameplate wattage.




[This message has been edited by Bjarney (edited 11-14-2004).]

Hi David,

I've also run U.S. power tools from the 110V site transformers as well, and never experienced any problems.

The "universal" motor is the one you will find in just about all hand-held power tools, and the frequency difference on these is of no great significance. In fact some universal motors are designed to be run on DC as well as AC (many older domestic vacuum cleaners had such a motor, for example).

These universal motors are all of the asynchronous type, meaning that the rotor speed is not locked to the supply frequency. Synchronous motors are found in such items as electric clocks (mechanical type), small fans, and older style record players and tape recorders.


Don't worry, you won't be zapped!

The 120V you get from a wall outlet in the United States has a "hot" line and a neutral, just as a 240V British socket provides a live and a neutral. In both cases, the neutral is grounded (earthed) at source, so there is no voltage between it and the earth. The live/hot line is then at 120 or 240V with respect to earth.

The British 110V site transformer has a transformer winding with the center-tap earthed. That means that the two supply lines are both "hot" -- There is 110V between the two wires, but only 55V between either wire and earth. The idea is that the reduced voltage to earth improves safety (and we've had debates about that in the past!).

In practice, as far as your portable power tools are concerned, that's of no consequence so long as you don't go poking around inside them with the power connected.

Most power tools have both power lines switched anyway.

All,

Thanks for the help.

I contacted Skill and this is what they said -

"Dear David,

Thank you for writing. The motor we use is neither synchronous nor asynchronous. It is a Universal Series motor. Since you have actually reached Skil USA customer service, if you have additional questions, please contact Skil UK through the following link"

I'm still a little confused though as there seems to be three types of motor - synchronous, asynchronous and universal.

David Lloyd



[This message has been edited by davelloyd (edited 11-19-2004).]

It sounds as though Skil customer service is confused, for the universal series motor is a type of asynchronous motors.

All motors must fall into the overall synchronous or asynchronous categories. Either the design of the motor synchronizes its speed to the supply frequency or it doesn't. The universal series type doesn't, therefore it is, by definition, an asynchronous motor.

here int he states our power can vary. you can goto House A and get a reading of 105v and 210v then go 10 houses down to house B supplied by the same power company and get 120v and 240v. it really depends on the precision of the transformers and line voltage drop here. doesn't do any damage here to things.

From University of Michigan found this:
Universal Motor Construction
Universal motors can operate on either AC or DC power. The rotor has coils that are connected to an external circuit through a commutator on the shaft, as shown in the schematic at right.

Note that the field in the rotor will oppose the field in the stator at any given moment, regardless of whether or not the polarity of the supply current changes with time. This feature gives the universal motor its unique characteristic.

The price of versatility is efficiency; universal motors are not as efficient as similarly-constructed AC and DC series motors

Hi Tinkerer, and welcome to ECN.

It's like most things -- A compromise between conflicting requirements. I seem to recall from many years ago reading that one of the adjustments made in the universal motor (as compared with a straight DC series motor) is that the commutation point is shifted a few degrees to better suit AC characteristics.

Maybe one of our guys more familiar with industrial motors can comment?

Rather than start a new thread, I thought I’d resurrect this one as it is most relevant.

As befits the familie Hutch, we are on the move once more, and this time will be heading for Blighty’s sultry shores – and yet another change in plugs in store! Plus this time I have a lot of 110-120V workshop stuff in tow that I have accumulated during my time in the USA. So I’m trying to plan ahead.

I’ve already split all the electrical stuff into “don’t bother”, “adapt it” and “no problem” sets – the workshop stuff fits into the middle category.

American TV’s fit into the former category and originally South African HiFi’s into the latter. If there’s anyone in the Denver area that would like to put in an offer on some US TV’s – PM me for a great deal!

My table and mitre saw are both rated at 15A (120V) and comprise the most thirsty of the workshop beasts. I am planning to utilize a worksite centre-tapped transformer in the interim but this strikes me as not necessarily the best in the long run. Depending on the workshop I would like to consider a fixed step-down transformer and NEMA sockets thus:


(Borrowed from www.mkelectric.co.uk )

Any ideas from the local troops on this, and whether the arrangement would be acceptable under local regs. How do radial circuits for 120V comply? Is there still a restriction on 50(?) sq. m per circuit? Your thoughts are appreciated.


[This message has been edited by Hutch (edited 02-06-2005).]

[This message has been edited by Hutch (edited 02-06-2005).]

Hi Ian!,
So you are on the move again?, Man you're hard to tie down!.
Anyhow, a socket without a switch on it, in England?.
Hmmm.

You sure get around Hutch!

Yes, the current IEE/BS7671 standard for a 20A radial circuit is a floor area not exceeding 50 sq. meters, although obviously that was designed with 240V BS1363 outlets in mind.

Whereas the ring circuit is still basically the same as it was 50 years ago (just a change from 1000 sq. ft. to 100 sq. m.) the areas and number of sockets for radial circuits have changed often and drastically over the years. It seems that the IEE has never quite been able to decide on what is "correct."

Even with the advent of the infamous part P, there's still no requirement to follow BS7671 in domestic installations anyway. (Not that you would be telling the local council about this wiring anyway, would you? ). I don't see any problem with installing a suitable transformer and running one or two 15 or 20A radial circuits for the 120V outlets. I've done the same in the past.

Switched sockets are really only an accepted convention. The (non-mandatory) IEE Regs. have only ever specified switches for sockets on D.C. supplies. There has never been any switch requirement on A.C., and unswitched BS1363 sockets are available.

[This message has been edited by pauluk (edited 02-07-2005).]

Thanks to Mike and Paul. As far as the local council is concerned I have no problem in telling them (if Part P demands it in a workshop) so long as they don’t come up with a load of unsubstantiated reasons why I should not install it thus. If there are regulations prohibiting this, it would be good to know ahead of time. I might be looking for a broad minded sparky in the Oxon/Bucks area !

I’ve seen the yellow, centre tapped 110V CEE sockets in an industrial setting up in Scotland but these look over-engineered and expensive for the domestic setting – hence me looking at the NEMA route, using MK’s Saudi Arabian sockets.

Interesting that the switches on sockets go back to the DC days. I’ve always wondered why they are so popular in Her Majesty’s current and former Dominions. I do confess that I like them and the current NEMA 6-15 in my workshop – serving the bench drill – has one.

I've seen 110V AC circuits used in Ireland for specialist purposes.

They used NEMA socket outlets fed on 16A circuits fused with standard neozed fuses rather than breakers.

I've also seen installations that used 15Amp BS546 sockets for 110V.

Definitely no chance of those overheating !


However, in any industrial or workshop installation the yellow CEEform sockets are required legally for 110V AC.

Also, they're not very expensive and are relatively easy to get. So perhaps not a bad sollution for your powertools!

you can easily buy extension cords and site transformers with those fittings.

[This message has been edited by djk (edited 02-08-2005).]