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Using a European motor appliance (vacuum cleaner) on a two-phase 240V U.S. supply

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Navegador

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Hi guys,

my house is wired so that I have both 120V and 240V outlets (phase+neutral and two phase setups), 60Hz. I'm in southeastern Brazil (most of the country is 240V 60Hz, but here in Rio we still use older 120V). Now, I've got this European vacuum cleaner, a very nice Miele S2, the plug fits Brazilian outlets but its label says 240V 50Hz. And in Europe (and elsewhere in Brazil) they use 240V in a phase+neutral setup rather than two-phase.

So here's the $300 question: will I fry or slowly destroy this nice vac if I plug it in my 240V, 60Hz, two-phase outlet? Is there something to be said about torque loss/power gains from operating a 50Hz motor in a 60Hz circuit? Most Miele motor photos on Google show only voltage but not frequency on the chassi, is it safe to assume it's a 'universal' motor?

Please help. Thanks!
 
Vacuum cleaners are pretty well exclusively Universal motors, but in any case 50/60Hz is close enough to make no difference (apart from the speed of synchronous motors of course) The strange 'two phase' system used in the USA, is no different to the single phase/neutral used elsewhere (which is usually one phase of a three phase distribution anyway).
 
The US system is best called split-phase. My friend has some two-phase motors when his shop was at one time two-phase.
See: https://en.wikipedia.org/wiki/Two-phase_electric_power

Split phase is basically single phase fed to the primary of a transformer. The secondary is center tapped and tied to ground.

You have a better chance operating stuff designed for 50 Hz on 60 Hz then the other way around.

Fixed per Navegador
 
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Funny, most of the internet seems to think that using a 50Hz motor on 60Hz is safer than the other way around. :confused:

I'm also worried about motor power loss from the 90 deg. vs. 180deg. phase difference in the 2 x 120V setup, is that a factor?
 
Navegador: Your correct. I fixed it in my post. Thanks.

I'm also worried about motor power loss from the 90 deg. vs. 180deg. phase difference in the 2 x 120V setup, is that a factor?

There is no phase difference. The US has 3 and 4 wire 240. One contains L1, L2 and Ground and the other L1, L2, N and Ground. An electric water heater can get away with L1, L2 and ground.
 
Here I have L1+N+Ground and L1+L2+Ground plugs. I'm total dummy when it comes to electrical engineering, hence my probably silly questions.
 
And that's what we have in the US. The potential between N and G = 0; the potential between ( L1 or L2) to N is 120 and from L1 to L2 240 V
 
Funny, most of the internet seems to think that using a 50Hz motor on 60Hz is safer than the other way around. :confused:

The difference is only small, it's of no consequence in almost ALL cases, and probably never in a domestic setting?.

I'm also worried about motor power loss from the 90 deg. vs. 180deg. phase difference in the 2 x 120V setup, is that a factor?

No, there is no phase difference, as KeepItSimpleStupid said, it's simply fed from the two ends of a centre-tapped transformer.
 
Hi,

Transformers and windings are designed with the line frequency in mind, but the difference between 50 and 60 Hz isnt so great that it would cause a huge problem. The main difference lies in the excitation current. For a 60Hz unit operating on 50Hz, the excitation current could be as high as about 20 percent higher, which seems significant, but the load current is usually much higher. For a 50Hz unit operating on 60Hz, the excitation current will actually be lower by roughly 20 percent, which means the unit operates cooler.

So yes there is a small difference which could make a difference when operating something made for 60Hz on 50Hz if it operates for long periods at a time, but for short runs like with a vacuum cleaner i doubt it will make much difference.

Lines coming into most homes are just single phase. They have two sides though so they are often called "split phase". This is not the same as a true multi phase line, because the two sides only differ in phase the same way a single line does, and this means it's just a regular line when loaded from the two sides rather than from just one side.
So for either 'side' we get 120vac, and loading across both sides gives us 240vac or what they often call 220vac. Either way you load it though it's still just single phase because there's only two wires for each loading scenario, and you cant have multi phase with just two wires. It's all about what the load sees, and that's always going to be single phase, at least in most homes here. In factories they often have three phase systems that are true three phase systems where the phases are 120 degrees apart. This means the although the voltages across any two phases still creates a single phase, the voltage calculation is a little different than just adding the two line voltages. I guess someone could order this for their home but i've never seen it myself.
 
In factories they often have three phase systems that are true three phase systems where the phases are 120 degrees apart. This means the although the voltages across any two phases still creates a single phase, the voltage calculation is a little different than just adding the two line voltages. I guess someone could order this for their home but i've never seen it myself.

I don't think you ever use it like that?, what would be the reason to do so? - and I doubt anything is made to operate under those bizarre conditions :D

I presume three phase in the USA would be 220/240V per phase rather than only 110/120V? (there seems little point in 3 phase 110V).
 
I don't think you ever use it like that?, what would be the reason to do so? - and I doubt anything is made to operate under those bizarre conditions :D

I presume three phase in the USA would be 220/240V per phase rather than only 110/120V? (there seems little point in 3 phase 110V).

Hi,

Not sure what you think is so bizarre. That someone would order 3 phase for their home? I think so too then.

Many three phase systems around here are four wire systems: three phase lines and one neutral, where the voltage is 120vac line to neutral and 208vac line to line.
 
Not sure what you think is so bizarre. That someone would order 3 phase for their home? I think so too then.

No, wanting to run something off only two phases of a three phase supply.

Interesting that they supply 110/120V three phase over there, seems pretty pointless - may as well have the higher voltage surely?.

Three phase is normally four wire, with the neutral feed usually being a thinner wire than the phase wires. To a suitable motor of course you normally don't supply the neutral as well as it's not needed.

Funnily enough we've recently taken out a small three phase goods lift/hoist at work (which is hopefully going to be refitted after the building work has been completed), and it had the thinnest wire you've ever seen feeding it :D The cable was Pyro (mineral insulated), three phase cable, only about the thickness of a pencil (if not a bit thinner) - so obviously not a very high wattage motor.
 
Hi Nigel,


No, wanting to run something off only two phases of a three phase supply.
Well actually what i meant there was to just explain that for any two wires, we can only have single phase, no matter what we do. For a 120v three phase system loading off of line A and B we would get 208vac and although phase A might be at 120 degrees and phase B at 240 degrees, to the load it just looks like single phase which we would call 0 degrees. So no matter how we use two wires, we always have single phase. This was more in line with the 220/110 volt system we were really talking about where we load either across one side or the other, or across the two 'outer' wires to get the 220vac.

Interesting that they supply 110/120V three phase over there, seems pretty pointless - may as well have the higher voltage surely?.

Three phase is normally four wire, with the neutral feed usually being a thinner wire than the phase wires. To a suitable motor of course you normally don't supply the neutral as well as it's not needed.
Pointless? Maybe so, but they use it a lot maybe because they started with 120vac single phase and worked their way up, little at a time :) They realized that 120vac three phase can transfer more power than single phase so it was better. Maybe not as good as a higher voltage, but still better. I often wish we had 220vac here as the standard instead of crappy 120vac (single phase for most homes) as that transfers more power per wire gauge as im sure you are aware of. I guess they felt 220v was more dangerous than 120v..

Funnily enough we've recently taken out a small three phase goods lift/hoist at work (which is hopefully going to be refitted after the building work has been completed), and it had the thinnest wire you've ever seen feeding it :D The cable was Pyro (mineral insulated), three phase cable, only about the thickness of a pencil (if not a bit thinner) - so obviously not a very high wattage motor.
Oh that's interesting. But we do know that the line current per phase will be much lower than a single phase line current for the same power load. Hopefully they didnt cut back too much though :)
 
Going up in freq is generally not as bad as going down, core saturation can happen if you lower the freq, big power trannies might have issues going from 60 to 50hz, but a universal motor will probably be fine from 50 to 60, speed shouldnt be affected as universal motors are not synchronous. The issue you might run into is that if the hoover has a speed control, ad your supply is 2 phase then both supply lines will be live, instead of a live and neutral (ground potential), this might mess up the speed control, you wont know without trying I spose.
 
Oh that's interesting. But we do know that the line current per phase will be much lower than a single phase line current for the same power load. Hopefully they didnt cut back too much though :)

I don't think they 'cut back' at all, I imagine the Pyro cable was more expensive than using thicker non-Pyro cable? (and costs more to install).

I had a look at the motor, but there's no wattage rating on it - still, it's worked flawlessly for over 50 years :D
 
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