Why did North America not use 220v

[Shannow]

Originally Posted By: kschachn

Well I did say "house"

That you did...but while we are there...

Power Stations are paid by the MWHr...VARs are a different service category and paid separately if contracted.

MDF factory that I commissioned in the 90s had DC pony motors to start their defibrator, as their access fee to the grid was based on inrush, not average load...(we just start them DOL)

 

[SHOZ]

Originally Posted By: JHZR2
Originally Posted By: kschachn
Please show me the amp meter attached to your house and explain how you are paying for amperes.

I will concede that my degree is a BSME, not BSEE. But I did work for several years in the electrical power generating industry.

Originally Posted By: d00df00d
Originally Posted By: kschachn
That's gotta be one of the dumbest posts I've ever seen. You pay for watt-hours, not amps. It's the same regardless of the voltage.

You pay for power, plain and simple.

Watts = volts * amps.

More volts means fewer amps needed to get the same wattage.


Actually, business and industry often pay for kVA, not kWh, power factor (could be off by 20%) being the difference.

But in the us it seems that we're not charged that way (yet).


My base rate is calculated by the kVA size of my transformer. But they use kWH as 1000X kVA.

 

[GMFan]

I work almost everyday around medium/high voltage switchgear and transformers anywhere from 5kV to 69kV. Doesn't matter what voltage I'm in front of...I have profound respect for it and it will kill you just as dead whatever the voltage is. In fact most equipment I've inspected which electrocuted a worker was usually low voltage down at the 208V utility panel. Current doesn't care if you're a copper wire or human. Heck, the last piece of equipment I inspected where a worker died was from 120V control voltage off a control transformer on a 480V alternator panel for a diesel generator.

As far as the 120V question nobody really knows to be honest. I did have a professor in school who when asked by a student as to why they use 220V in China vs 120V and his response was "they have more workers to spare."

 

[440Magnum]

Originally Posted By: expat
Originally Posted By: badtlc
Originally Posted By: expat
It seems most of the world (other than some 3rd world countries) use 220v-230v
which I imagine is more efficient.

How come we got stuck with 110V?


Your house gets 240V from the utility.



No it doesn't, it gets 110-120v twice.

Perhaps someone can explain the advantages/disadvantages of 240v verses 120v x2


No, it doesn't get 120 twice.

What is delivered from the pole to your house is "220V" (its actually more like 240V) DIFFERENTIAL voltage on a pair of wires. That means, two wires with 220VAC relative to each other. If you take ONE of those wires and reference it to ground potential, it measures out 120 volts. So the 120 volt outlets we have in our homes are each one "leg" of the actual 220V feed referenced to ground (called "Neutral" and wired back to a separate ground point than the "ground" wire- confused yet?) instead of to the other "leg" of the feed.

I actually do not know (nor have I seen it thus far in the thread) WHY this was originally done. Its pretty handy in that 110-120V is actually safer and plenty sufficient for most loads, leaving 220V for big items like electric furnaces, heat pumps, air conditioners, motors over 2 horsepower continuous-duty, and so on. But it does mean that depending on what you're running where in your house, the load seen at the transformer can be unbalanced. Not really a problem, just that the transformer has to be sized a little on the larger side to allow for that.

But all that's really irrelevant, since electricity is DISTRIBUTED in three-phase and at much higher voltage (12,000 to 15,000 for smallest overhead distribution lines in neighborhoods, several hundred thousand volts for big cross-country transmission lines). Each leg of a 3-phase line can drive a smaller distribution line that the utility hangs single-phase house transformers from, so generally several whole houses in a row on a given block are fed from only 1 leg of a 3-phase line. And THAT can also make the 3-phase distribution imbalanced, and that is actually (ultimately) seen at the power plants. But the system is so big that it the imbalances are tiny fractions of the total load.

The better question, to me, is "why isn't EVERY house provided with three-phase?" And the answer to that is (in my opinion) "silly northerners and their cool weather." The northeast was electrified first, and the only loads were light bulbs, fans, and, later, small refrigerators. If the southwest had been more populous, central AC would have come earlier, the need for 3-phase delivered to homes would have been perceived as greater, and 3-phase power would have (probably) been the norm. As it is, the HVAC companies invested a whole lot of money over the last 50 years to make single-phase compressors and blower motors very efficient, and they're less inherently efficient than 3-phase motors. And thats why really BIG stuff- office building chillers, 20+ horsepower shop compressor motors, big machine tools, etc.- ARE all three-phase. Well, that and the fact that 3-phase motors don't "hum." Their torque delivery is constant, not on/off at 120 Hz the way single-phase motors do.

 

[SHOZ]

You can get small load converters to turn 220v single phase into 220v 3 phase. Up to 5 hp I think. But three phase at the house is pretty expensive as you need three transformers.

 

[john_pifer]

Good thread! Subscribed!

I've been doing a lot of reading about electricity generation and distribution lately.

I don't understand everything y'all are talking about, but I'm trying to learn!

Here's a question for you: I have read that 3-phase AC can provide a "rotating magnetic field" for an electric motor. What does that mean, exactly?

I am an aircraft mechanic, and I work at a repair station, doing heavy maintenance on regional airliners.

We use small, portable ground power units (GPUs) that supply 400Hz AC to power the electrical systems on the aircraft without having to run the engines or auxiliary power unit.

I've noticed that we have some receptacles in our hangar that supply 480v, 3-phase power, and they have been labeled "CCW Rotation." I'm assuming that means that the rotating magnetic field they provide for large electric motors is counter-clockwise rotation? And, what makes it clockwise rotation or counter-clockwise rotation? The direction the generator turns?

I forget whether our GPUs plug into that 480v receptacle or not... I'll have to check Sunday when I go back to work.

What is interesting is, our hangars actually do have 400hz AC receptacles, but we don't plug the aircraft into them directly...we use the GPUs. Again, I forget the rating of the receptacles the GPUs are plugged up to. I've often wondered why we are using GPUs when the facility actually has 400Hz AC available.

I'm not sure on the specifics of how that 400Hz AC is generated, but I have seen a room where there is what looks to me like a generator... Maybe it's a 400Hz generator being turned by a motor running on 480v 3-phase @ the standard 60Hz?

Someone here mentioned that he designs distribution systems for industrial applications... Maybe you can fill me in?

(For those who might not know, most large aircraft use AC @ 400Hz so that the transformers can be made much smaller.)

 

[Rick in PA]

Ah, smaller transformers, of course. I always wondered about 400Hz on airplanes. Thanks.

 

[Shannow]

Originally Posted By: john_pifer
Here's a question for you: I have read that 3-phase AC can provide a "rotating magnetic field" for an electric motor. What does that mean, exactly?


Originally Posted By: Shannow
Originally Posted By: expat
3 Phase (I understand) is 120v x 3 wires out of Phase. How the 3 all get out of phase, I don't know

Single phase is a single rotating magnet in a coil...

Look down a shaft, and place a magnet across it, so North is up, south is down. Have a coil arranged going in and out of page. Rotate magnet, and as the field crosses the coil you get a sin wave voltage current, on a single "phase".

Spin the shaft at 3,600 RPM, and you've got a single phase 60Hz.

Make another two phases, and mount them at 120 degrees from each other, do the same, and there's 3 phase.


The rotating magnetic field is what's left at the other end when you hook up a motor with three coils at 120 degrees.

The three phases, one hooked to each coil create a rotating magnetic "North-South" that the rotor gets hooked up to and dragged along with.

A squirrel cage literally gets dragged around with the field.

A permanent magnet rotor (or a wound rotor with excitation) will get dragged around in absolute lock step with the rotating field.

 

[edwardh1]

Originally Posted By: OneEyeJack
When I lived in Greece the outlets for the bathroom were outside the bathroom, not inside like I expected. Also the Greeks has less use for electricity in the bathroom than here in America.


no electric tooth brushes or hair dryers or curling irons?

 

[leeharvey418]

Originally Posted By: edwardh1
Originally Posted By: OneEyeJack
When I lived in Greece the outlets for the bathroom were outside the bathroom, not inside like I expected. Also the Greeks has less use for electricity in the bathroom than here in America.


no electric tooth brushes or hair dryers or curling irons?

Then how do the men curl their back hair?

 

[SHOZ]

Originally Posted By: john_pifer
Good thread! Subscribed!

I've been doing a lot of reading about electricity generation and distribution lately.

I don't understand everything y'all are talking about, but I'm trying to learn!

Here's a question for you: I have read that 3-phase AC can provide a "rotating magnetic field" for an electric motor. What does that mean, exactly?

I am an aircraft mechanic, and I work at a repair station, doing heavy maintenance on regional airliners.

We use small, portable ground power units (GPUs) that supply 400Hz AC to power the electrical systems on the aircraft without having to run the engines or auxiliary power unit.

I've noticed that we have some receptacles in our hangar that supply 480v, 3-phase power, and they have been labeled "CCW Rotation." I'm assuming that means that the rotating magnetic field they provide for large electric motors is counter-clockwise rotation? And, what makes it clockwise rotation or counter-clockwise rotation? The direction the generator turns?

I forget whether our GPUs plug into that 480v receptacle or not... I'll have to check Sunday when I go back to work.

What is interesting is, our hangars actually do have 400hz AC receptacles, but we don't plug the aircraft into them directly...we use the GPUs. Again, I forget the rating of the receptacles the GPUs are plugged up to. I've often wondered why we are using GPUs when the facility actually has 400Hz AC available.

I'm not sure on the specifics of how that 400Hz AC is generated, but I have seen a room where there is what looks to me like a generator... Maybe it's a 400Hz generator being turned by a motor running on 480v 3-phase @ the standard 60Hz?

Someone here mentioned that he designs distribution systems for industrial applications... Maybe you can fill me in?

(For those who might not know, most large aircraft use AC @ 400Hz so that the transformers can be made much smaller.)


You change direction of 3 phase motors by swapping two of the 277v leads. Doesn't make any difference which two.

 

[eljefino]

Originally Posted By: leeharvey418
Originally Posted By: edwardh1
Originally Posted By: OneEyeJack
When I lived in Greece the outlets for the bathroom were outside the bathroom, not inside like I expected. Also the Greeks has less use for electricity in the bathroom than here in America.


no electric tooth brushes or hair dryers or curling irons?

Then how do the men curl their back hair?


Willpower!

 

[leeharvey418]

Originally Posted By: eljefino
Originally Posted By: leeharvey418
Originally Posted By: edwardh1
Originally Posted By: OneEyeJack
When I lived in Greece the outlets for the bathroom were outside the bathroom, not inside like I expected. Also the Greeks has less use for electricity in the bathroom than here in America.


no electric tooth brushes or hair dryers or curling irons?

Then how do the men curl their back hair?


Willpower!

Okay... then how do the women do it?

 

[Vikas]

Think of this way:-

Somewhere far away generator spins and converts mechanical energy in to electrical energy. That energy comes out on the three legs of the wire. So if you hook up "inverse generator" to the end of those three wires, you get that motor rotating.

Too simplified but rotating magnetic field creates electricity and then the same electricity can create rotating magnetic field. If I remember, Maxwell's theory goes through all the mathematics to prove this.

By the way, Thanks Magnum, your explanation was the best in this topic.

 

[440Magnum]

Originally Posted By: john_pifer
Good thread! Subscribed!


Here's a question for you: I have read that 3-phase AC can provide a "rotating magnetic field" for an electric motor. What does that mean, exactly?


Well, think of an old-fashioned metal "bar" magnet with a 'North' pole, and a 'South' pole. Now think of three stator (field) coils of a 3-phase motor, hooked up to the three phases of an electrical feed. It "falls out of the mathematics" of the way three sine waves 120-degrees apart add together, that the magnetic field in the center of those three coils is exactly what you would get if you stuck a bar magnet in the middle of them and rotated it. The "north" and "south" ends of the field in the center of the three stator coils rotates in a complete circle 60 times per second, so that if you put an actual bar magnet in the center of the field, it would want to spin at 3600 RPM. In practice, "synchronous" motors work that way- the rotor is magnetically locked to the rotating magnetic field. More common "induction" motors spin slightly slower than the magnetic field, because that 'slip' is needed to induce (hence the name 'induction motor') currents in the rotor.

For slower RPM, add more poles to the motor. 6 coils runs at half the speed of a 3 coil motor.