220 vs 240 volt

[Stan Coryell]

I once drew out the 3-phase waveforms and subtracted one wave from another other to see why.

The power company here, out in our rural area with no industry around, recently replaced all the poles on the nearest country road and ran wires on 3-phase hangers. But they only ran two wires in addition to ground instead of three. I assume they did that to allow balancing the load between different areas, either now or in the future, and let them easily change to 3-phase if needed. Maybe someday when I don't have anything else to do I'll drive around and see if some side streets are fed by different phases.

The poles, BTW, are much taller and set back further from the road than the original. They cut down a LOT of trees. I could have picked up 200 logs just along the short road our lane connects too.

The utility added a circuit or a phase. It's also likely the added circuit is a higher voltage. They may plan on replacing the distribution transformers one at a time and feeding them with the higher voltage. This is common here. A lot of distribution power is 4 kv feed from small substations that are 13.2 kv or 34.4 kv primary. Most of this equipment is from the late 40's into the 70's.

Once the new 34kv and 4kv system is strung and new poles are set change over begins one transformer at a time. After changeover, the 4Kv circuit is swapped to 34 kv
and used for redundancy.

Distribution (and transmission) are typically in a ring configuration. Picture a wagon wheel. The hub is the substation. The spokes are circuits from the substation feeding the ring buss (the perimeter of the wheel). If any failure occurs in the distribution, a downed pole for instance, switches can be operated to isolate the bad "spoke".

[Donald G. Burns]

A few places in the USA have 208 volt power too. I believe the area around Oxnard & Ventura, CA is one of these.

[Doug Dawson]

220, 230, 240v are usually different names for the same power. The numbers have changed over the years, at one time the standard was 220 volt. Sometimes numbers are used out of habit. (Some purists take offense at saying 220v) I think these days 240v is the "nominal" supply voltage with +/- 5% variance allowed for 228V to 252V. Checking with a meter will probably show the voltage varies during the day. In some locations this varies more than others.

On a 20amp circuit with 12ga wire with a nominal 120V, it’s not unusual to see an 8 or 9 percent voltage drop at the receptacle when running a 15amp load, which would put the voltage at the receptacle to roughly 110V, which is what the device would see. Even 5 percent is common in new construction. Something to think about. Machines have to be able to handle this.

[Stan Coryell]

A few places in the USA have 208 volt power too. I believe the area around Oxnard & Ventura, CA is one of these.

It's used here as well. 120/208 Y. 120 volt phase to ground and 208 volt phase to phase. The utility company only needs two transformers to produce this. It's popular in small restaurants and retail because it provides 3 phase for the air conditioning equipment, while also providing 120 volts for receptacles. As opposed to 240 volt delta. 120 phase to ground on two phases, 208 volts to ground on the other phase, usually B (sometimes A phase). The "high leg", 208 volts, is essentially unusable.

277/ 480 is more frequent in an industrial setting because of the need for transformers to provide 120 volts. Also, disconnects and devices rated above 300 volts cost more as a result of increased arc flash hazards. Lighting circuits would typically be 277 volts.

[Bruce King]

On a 20amp circuit with 12ga wire with a nominal 120V, it’s not unusual to see an 8 or 9 percent voltage drop at the receptacle when running a 15amp load, which would put the voltage at the receptacle to roughly 110V, which is what the device would see. Even 5 percent is common in new construction. Something to think about. Machines have to be able to handle this.

Those are extreme voltage drops due to very long runs or loose connections.
https://www.calculator.net/voltage-d...s=15&x=63&y=27

[Doug Dawson]

Those are extreme voltage drops due to very long runs or loose connections.
https://www.calculator.net/voltage-d...s=15&x=63&y=27

No loose connections (verified) and not so extreme, but often towards the end of several receptacles. And note the load (I have load testers, and systematically check this stuff.)

BTW this is a good reason for every receptacle running heavy machinery to have its own home run.

[Christopher Herzog]

My dad used to tell stories of the old hog houses using 200v. His term of endearment for it was the bastard phase.

[John K Jordan]

... The actual voltage you'd measure with an oscilloscope, where you could see the wave-form, would be varying between +172V and -172V 60 times per second. ...

Just for grins, I turned on my oscilloscope just now and checked line voltage on one leg in my shop, relative to ground. I use the scope quite a bit but for some reason never looked at the AC.

I measured:

Vmax: 172v to 175v
Vmin: -172v
Vrms: 121v
Freq: 59.8Hz to 60.1Hz

(The digital scope makes these measurement easy!)

Speaking of 3-phase: Some years ago I was doing electrical work at a missionary friend's children's camp in the middle of Mexico. Everyone had 3-phase if they wanted it which surprised me given that NO one in the town even had a telephone - you had to walk to the phone company to make or get a call. I saw some of the most horrifying wiring ever - a pair of bare 120v AC wires stapled down the wall inside a store to power a receptacle; a 50amp breaker feeding 14gage romex 150ft across the wooden ceiling joists to a water heater on the other end of the building... You couldn't buy breakers or wire anywhere within a 5 hr drive. It was two years before I got back there with supplies.

JKJ

[Rollie Meyers]

Or in my shop in CA: 120+120+220 = 240+-, 240+-, 240+-.

Two of the CNC machines were on transformers. One *needed* 380 (European), the other wanted 208 (Japanese). Service Tech strongly suggested stepping it down in case of any warranty issues.

If you are in California you do not have 220, the high leg is 208V, Japanese power is 200V, With PG&E they offer 120/240V 1Ø, 120/240V▲ 3Ø, 208Y/120V, 480Y/277V, and those are it. 240V▲ 3Ø 3-wire, 480V▲ 3Ø 3-wire, are only available to existing customers. Similar requirements in effect for Southern CA Edison, except they do not like 120/240V3Ø▲.

[Richard Coers]

Edison chose 110v to power his working lights. Current pushed through lines was based off that, at 110, and 220 volts, until sometime in the 1930's, it was standardized, and upped in voltage to 120, and 240, to better allow for distances of lines. 110/220 is still an old carryover naming for the same thing. My Parents' generation always still called it 110, and 220, because that's what it was when they were growing up, and that has just carried over, now for several generations.

Maybe that number is even in dispute, "The direct-current D.C. system generated and distributed electrical power at the same voltage (120-220 v), as that used by the electricity recipient customer's lamps and motors." https://ethw.org/Edison%27s_Electric_Light_and_Power_System

[Warren Lake]

Here is my post. Out of my scope to understand it but heard the buzzing loud and clear, likely more in tune to it from an audio past. Power talk makes me remember seeing a gaggle of birds come down to land on huge towers and lines and the big bang that blew out all the street lights for miles. Roasted a lot of birds. That was a day I wish I had a dash camera then I saw them come down to land and by the time the bang happened would have been too much beside me to capture it.


P1360451A.jpg P1360459A.jpg

[Curt Harms]

There have been High Voltage DC transmission lines in the US for over 30 years. I believe the first was built between Washington State and LA in the 70s. There have been quite a few built since. They are quite common in Europe,China and Japan. The big advantage is significantly lower power loss in long distance transmission due to the complete lack of reactive loss.

Then why did AC win over DC? I thought the primary reason is that AC can be sent over long distances, DC can't. Or is that only true at low voltages?

[Randy Heinemann]

All - I have seen some cabinet saws advertising 220 v 3 hp and others 240 v up. Do I need to wire my shop differently or does both get treated the same?

One thing . . . I was told by Jet (JPW) Support, when I was having a bit of trouble with my jointer, that I should check the actual voltage at the outlet because Jet's requirements were to have a full 240 volts at the outlet. Mine was OK, but it's my understanding that, for various reasons, the actual voltage at the outlet could be less than 240 V. I'm no expert on electrical issues but that seemed to be important to the Jet tech support guy.

[Bruce King]

Then why did AC win over DC? I thought the primary reason is that AC can be sent over long distances, DC can't. Or is that only true at low voltages?

Yes, must be high voltage DC. It takes A/C to develop those DC high voltage circuits. You can build a battery DC to high voltage DC circuit but it’s lower amps unless you have a huge battery bank.

[Bruce King]

One thing . . . I was told by Jet (JPW) Support, when I was having a bit of trouble with my jointer, that I should check the actual voltage at the outlet because Jet's requirements were to have a full 240 volts at the outlet. Mine was OK, but it's my understanding that, for various reasons, the actual voltage at the outlet could be less than 240 V. I'm no expert on electrical issues but that seemed to be important to the Jet tech support guy.

The tech support guy is just trying to eliminate a power issue by getting you to check it. It will still perform at 99.9 % if you had 235v.