Harmonizing the 2nd lowest American utilization voltage.. 208 and 240v

[Besoeker]

That's why we have different plug configurations for different voltages (and for different current ratings, for that matter). Perhaps not as simple as the UK/EU method, but still effective for preventing plugging things into the wrong voltage.

Yes. I understand your point..
Mine was that there is no wrong voltage here for domestic appliances.

I've never heard of somebody even trying to plug their 240V range or dryer (pretty much the only cord-connected residential appliances to use 240V) into a 120V receptacle, let alone succeeding. If anyone has done this, they would have to have hacked off the cord and replaced it with a 120V cord--not something even your most boneheaded homeowner is likely to do (then again, maybe I just don't know the right kind of boneheads). The same is true of trying to plug a table lamp into the 240V range or dryer receptacle.
Of course, now that I've put this out there, somebody else will come along with a link to a news article about someone getting electrocuted or burning down their house when they somehow managed to plug a microwave into the range receptacle. :roll:

Yep. Nothing is foolproof to a sufficiently talented fool.

 

[GoldDigger]

That's just plain wrong. It isn't smaller.

It certainly is not physically smaller, with the need for more iron in its core and the same amount of copper. But perhaps the available short circuit current might be less for some reason?

 

[Besoeker]

It certainly is not physically smaller, with the need for more iron in its core and the same amount of copper. But perhaps the available short circuit current might be less for some reason?

That would depend on the transformer design.
Short circuit current also depends on external cabling. At 60Hz the impedance of that would be greater than at 50Hz so that would reduce short circuit current at the load.

Maybe our mutual friend, the maharajah, can educate us on the finer points.

 

[kwired]

It is dual rated. It is not that a resistor rated at particular voltage should not be operated at lower voltage; it will not give its rated heat output.

How did you ever come up with that conclusion?:roll:

Did you know if you reduce voltage to an incandescent lamp you don't get the rated output of the lamp either?hmy:

That's why we have different plug configurations for different voltages (and for different current ratings, for that matter). Perhaps not as simple as the UK/EU method, but still effective for preventing plugging things into the wrong voltage.

I've never heard of somebody even trying to plug their 240V range or dryer (pretty much the only cord-connected residential appliances to use 240V) into a 120V receptacle, let alone succeeding. If anyone has done this, they would have to have hacked off the cord and replaced it with a 120V cord--not something even your most boneheaded homeowner is likely to do (then again, maybe I just don't know the right kind of boneheads). The same is true of trying to plug a table lamp into the 240V range or dryer receptacle.

Of course, now that I've put this out there, somebody else will come along with a link to a news article about someone getting electrocuted or burning down their house when they somehow managed to plug a microwave into the range receptacle. :roll:

Old saying goes something like - you can't idiot proof everything, if you do, along will come an improved idiot.

 

[Sahib]

It certainly is not physically smaller, with the need for more iron in its core and the same amount of copper. But perhaps the available short circuit current might be less for some reason?

For 60Hz, the current taken by the transformer is less.
For 50Hz, it is more requiring more iron as you stated.
But by using thinner coil wire, the current can be kept same as in 60Hz without increasing iron size. So the coil size would be smaller and so the overall size of 50Hz transformer is smaller and so the arc hazard is lesser.

 

[GoldDigger]

For 60Hz, the current taken by the transformer is less.
For 50Hz, it is more requiring more iron as you stated.
But by using thinner coil wire, the current can be kept same as in 60Hz without increasing iron size. So the coil size would be smaller and so the overall size of 50Hz transformer is smaller and so the arc hazard is lesser.

OK, my questions:

1. Why is the current required for a given kVA less? I expect that is more because of a higher voltage than because of a different frequency. Which is not what the original statement asserted.
2. Yes, I suppose that the use of thinner wire (which is NOT because of the frequency!) could allow tighter coupling of the windings to a physically smaller core, but the maximum magnetic flux in the core before saturation will still have to be higher for any given kVA rating at 50 Hz than at 60 Hz, so I am skeptical that the end result will be a smaller core.
3. Just why, in terms of physics, does a smaller transformer necessarily translate to a lower arc hazard? I find that a very hard generalization to justify. I could, again, see a higher voltage resulting in a lower incident energy rating under some circumstances, as discussed elsewhere.

 

[Besoeker]

For 60Hz, the current taken by the transformer is less.
For 50Hz, it is more requiring more iron as you stated.
But by using thinner coil wire, the current can be kept same as in 60Hz without increasing iron size. So the coil size would be smaller and so the overall size of 50Hz transformer is smaller and so the arc hazard is lesser.

Ho hum.....
Why do you think aircraft use 400Hz?

 

[Sahib]

1. Why is the current required for a given kVA less? I expect that is more because of a higher voltage than because of a different frequency. Which is not what the original statement asserted.

Higher the frequency, lower the AC current in an inductive circuit. So to bring the higher value current at a lower frequency to the same value at the higher frequency for a given voltage and given output KVA at the higher frequency, the resistance of the inductive circuit need to be increased.

2. I suppose that the use of thinner wire (which is NOT because of the frequency!) could allow tighter coupling of the windings to a physically smaller core, but the maximum magnetic flux in the core before saturation will still have to be higher for any given kVA rating at 50 Hz than at 60 Hz, so I am skeptical that the end result will be a smaller core.

As in 60 Hz
1) Core size same.
2)Current same
3)No of turns same
4)KVA same for 50Hz transformer. Only cross sectional area of coil wire reduced. So core flux density does not change. Due to reduction in coil size, the overall size of 50 Hz transformer is smaller.

3. Just why, in terms of physics, does a smaller transformer necessarily translate to a lower arc hazard?

Reduction in size of 50Hz transformer due to decrease in coil size.
Decrease in coil sizer due to thinner coil wire.
Increase in resistance of coil wire due to thinner coil wire.
Lesser arc hazard due to increase in resistance of coil wire of 50 Hz transformer.

 

[GoldDigger]

Higher the frequency, lower the AC current in an inductive circuit. So to bring the higher value current at a lower frequency to the same value at the higher frequency for a given voltage and given output KVA at the higher frequency, the resistance of the inductive circuit need to be increased.

I think that you have two fundamental problems here:

1. For a higher frequency, the current in a given inductor for a given voltage will be lower. Therefore the magnetizing current in the 50 Hz transformer will be higher for the same voltage. That requires more current, not less, and more energy loss. Or else you increase the inductance, not the resistance.
2. The magnetizing current does not really matter. We are looking at the transferred power between primary and secondary, not the magnetizing current.
And there is no avoiding the fact that the power is V x I, which has no frequency dependence at all. The only thing that will change with frequency, all other things being equal, will be the power factor of the transformer input for a given power level.

Reduction in size of 50Hz transformer due to decrease in coil size. NO.
Decrease in coil sizer due to thinner coil wire. NO.
Increase in resistance of coil wire due to thinner coil wire. If the wire were thinner, fine, but it is not.
Lesser arc hazard due to increase in resistance of coil wire of 50 Hz transformer. Ditto.

 

[Sahib]

golddigger:
It is better we open another thread to discuss the matter further.
Are you agreeing to do it?

 

[GoldDigger]

golddigger:
It is better we open another thread to discuss the matter further.
Are you agreeing to do it?

Go ahead, please.

Please do it on my behalf with your opening remarks.

Ok. Tomorrow.

 

[Sahib]

Please do it on my behalf with your opening remarks.

 

[Sahib]

Does what? Mentions 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480?
Not sure what point you were making.

277/480V is not permitted in residence in US unlike 230/400V is permitted in residence in EU.

And 120-0-120 presents an even greater one.

But not as hazardous as 230/400V permitted in residence in EU.

Countries in the EU have 230V single phase as the nominal voltage.

The article does not state that electrocutions are lesser in 230V single phase using EU countries.

 

[Besoeker]

277/480V is not permitted in residence in US unlike 230/400V is permitted in residence in EU.

The discussion is not limited to just residences.
The mention of 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480 does not limit it to residential.

But not as hazardous as 230/400V permitted in residence in EU.

Very, very few residences have 400V. I'd guess Buckingham Palace does.
And there are are no domestic appliances that use 400V. They are all single phase 230V. There are strict rules about where different phases can be located physically in relation to each other so, other than at the incoming terminals there is almost zero chance of anyone getting a 400V belt.

The article does not state that electrocutions are lesser in 230V single phase using EU countries.

Read the abstract again. Which countries are mentioned?

 

[Sahib]

The discussion is not limited to just residences.
The mention of 120/208/240/277/480 from 120/208, 120/240, 240/480(uncommon), 277/480 does not limit it to residential.

It is just one aspect of discussion which shows even with different voltages a US home can be safer than a EU home in certain circumstances.

Very, very few residences have 400V. I'd guess Buckingham Palace does.

May be so in developed countries. But in developing countries more usage of 3 phase supply.

And there are are no domestic appliances that use 400V. They are all single phase 230V. There are strict rules about where different phases can be located physically in relation to each other so, other than at the incoming terminals there is almost zero chance of anyone getting a 400V belt.

Nor does an appliance in a US home.

Read the abstract again. Which countries are mentioned?

The article originated in India and in the Abstract it talks about more fatalities due to electrocution here compared to Bulgaria and Canada and 230V single phase supply is used here.

 

[JoeStillman]

...Not so sure about the first. Metric or SI units are being used on some things. I think there will be a shift to conform with the rest of the world for ease of trading.

The American automotive industry is a good example. They have gone a long way toward making cars metric. I imagine we don't export much pipe and wire though. I have never encountered metric-sized conduits and conductors.

I'll bet they don't even use British Thermal Units in Britain anymore. I'm just glad volts and amps are already meteric.

 

[kwired]

It is just one aspect of discussion which shows even with different voltages a US home can be safer than a EU home in certain circumstances.

May be so in developed countries. But in developing countries more usage of 3 phase supply.

Nor does an appliance in a US home.

The article originated in India and in the Abstract it talks about more fatalities due to electrocution here compared to Bulgaria and Canada and 230V single phase supply is used here.

What is used as a code in India and how strict is enforcement? Installation practices/requirements may have a lot to do with electrocution incidents. 230 volts is still 230 volts whether it is in US, Canada, India, or on the moon, it doesn't discriminate to find victims.

 

[dereckbc]

I have not read through all the replies, but the USA electrical architectural is really a poor design as a result of a feud between Westinghouse and Edison who set the standards. It was a compromise between the two. Edison won for using lower voltage of 110, and Westinghouse won using AC. Result was a poor compromise. The first issue is the unbalanced (Asymmetrical) nature of 240/120 which causes unwanted currents in ground circuits. There is no good way to prevent it when using 120 volts in the conventional USA electric architectural. The second issue of course is low voltage of 120. It limits the amount of power that can be used and inefficient. Typical branch circuits are limited to 20 amps and that limits power to 2400/1920 VA.

Other countries like Europe electrical systems are symmetrical or balanced 200 to 240 volt AC. The higher voltages while still being as safe as 120 asymmetrical are more efficient and allow much higher power levels. Unfortunately in the USA it would be to costly to switch, although it could be implemented making appliances being able to use either 120 or 240 VAC. 240 VAC single phase is symmetrical

 

[kwired]

I have not read through all the replies, but the USA electrical architectural is really a poor design as a result of a feud between Westinghouse and Edison who set the standards. It was a compromise between the two. Edison won for using lower voltage of 110, and Westinghouse won using AC. Result was a poor compromise. The first issue is the unbalanced (Asymmetrical) nature of 240/120 which causes unwanted currents in ground circuits. There is no good way to prevent it when using 120 volts in the conventional USA electric architectural. The second issue of course is low voltage of 120. It limits the amount of power that can be used and inefficient. Typical branch circuits are limited to 20 amps and that limits power to 2400/1920 VA.

Other countries like Europe electrical systems are symmetrical or balanced 200 to 240 volt AC. The higher voltages while still being as safe as 120 asymmetrical are more efficient and allow much higher power levels. Unfortunately in the USA it would be to costly to switch, although it could be implemented making appliances being able to use either 120 or 240 VAC. 240 VAC single phase is symmetrical

But don't you just move the unbalance to a different point of the distribution in typical European systems?

240 volts is line to neutral voltage of a 415/240 volt wye system at some point in many cases.

 

[mgookin]

Let's crawl into dreamland for a moment. We're all going to go to bed tonight and wake up tomorrow with the best electrical generation and distribution system and everyone gets free electrical appliances, devices, etc., all compliments of the tooth fairy. All we have to do is make up our mind, and agree, on what we want.

We're right back to the original debate. AC or DC? (The last DC grid in NYC was shut down in 2007 from what I understand). How many volts per phase? How many phases? What frequency? What kind of power? Is it fossil, nuclear, wind, wave, etc.?

Ask that many questions and you'll end up with more complicated systems than you have now.

What we have works. It's not that tough to manufacture something that works worldwide. Some modifications here and there, but overall, what we have works quite well.

One day when we have no grid you'll be able to produce onsite whatever power you want.

Until then, we have what we have and we know how to utilize it to meet our needs.