220 vs 240 volt

[jeff friedman]

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?

[Doug Dawson]

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?
The technical standard (for what is supplied) is 234 something, but whether you get that depends on where you are along the line, so it rarely happens. It’s all just in that range.

[Bruce Volden]

They are the same.

[John K Jordan]

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?

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.

A check of electric motors around my shop showed most of them list 230 volts on the nameplate.

JKJ

[Tom M King]

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.

[Frank Pratt]

Yep, 120/240 for single phase (not derived from a 3 phase system) power. No such thing as 110 or 220 in Canada or US. A 3 phase service, or single phase derived from a 3 phase system is 120/208V.

[Jim Becker]

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?
North American power grid is pretty much 240v for residential supply. Marketing materials have never caught up. You'll be fine with gear listed for 220/230/240.

[Warren Lake]

In school they taught us 1 + 1 is 2. So 110 +110 is 220 so much for that lesson :)

[Mike Henderson]

In school they taught us 1 + 1 is 2. So 110 +110 is 220 so much for that lesson :)

Actually, the lower voltage is always half the higher voltage in a single phase system. The reason is that the transformer on the pole is center tapped. The voltage between the two outside lines are the higher voltage (240 volts) and the voltage between the center tap and either of the outside lines is 120 volts.

In the US residential distribution system, the center tap is always grounded. Even when you have a circuit that supplies the higher voltage, the voltage to ground from either side of the supply is half the line-to-line voltage of the circuit. It's a good safety factor.

In the UK (and I assume other places) three phase is brought to the residential area and a Y transformer system is used. The center tap of the Y is grounded and the supply to the house is taken between one hot line and the center tap of the Y. At least that's my understanding.

Mike

[Rod Sheridan]

In school they taught us 1 + 1 is 2. So 110 +110 is 220 so much for that lesson :)
Unless it”$ three phase, then 120 + 120 = 208:D


Regards, Rod

[roger wiegand]

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.

Not quite. Edison was the primary proponent of DC power and his system used 110 VDC from end to end. George Westinghouse as the champion of AC power upped the voltages for transmission, making for a much more efficient network, taking advantage of the possibility of step-up/step-down transformers with alternating current. Edison could only distribute within a relatively few miles of his generating stations at 110 v.

The Battle of the Currents is a fascinating story, putting VHS vs Betamax or Mac vs PC to shame for its viciousness.

[Tom M King]

Thanks. I forgot about the AC/DC wars.

[David Kumm]

I don't think anyone who competed with Edison had an easy life. To confuse things more, some old machines, particularly from the Northeast have old two phase motors or 200v three phase. A vfd handles the 200v but nothing really handles the two phase very well. Dave

[Frank Pratt]

And DC is likely to replace AC for the large high voltage distribution lines. Less loses with DC & modern low cost electronics needed to change the voltage is removing the high infrastructure cost barrier.

[Warren Lake]

Didnt Tesla pay part in this? not the business man one but the brilliant one (guess this one is as well). THe old guy always told me when you look for a shop make sure three phase. Now i look out my window and they ran three phase think 50,000 volts forgot across my driveway. When it rained my pole used to buzz like a cicada. I called in and they never showed. Month or two after guy visiting a neighbour said I used to be an inspector and your pole is wired wrong. I told him it buzzes and its burned up top as well, he said dont go near it when its wet. I called back sent photos of the burning and what the guy said and they were here next day. Guy who did the work said some days he is not paid enough. It wasnt the Witchita Lineman.

[Bill Dufour]

In school they taught us 1 + 1 is 2. So 110 +110 is 220 so much for that lesson :)


True, but 120 +120 =240. That process is called generalizing what you learned in class into real world examples.
110 changed into 120 about when biplanes got replaced by monoplanes. 120 was firmly established before the Army air corp became the air force.
Bill D

[Bill Dufour]

Edison invented the electric chair to demonstrate how dangerous AC was. This was after he electrocuted an Elephant in a public spectacle to show how you should only use nice safe dc. Which he just happend to have the patents on. While he had no rights to ac power.
Bil lD

[Bruce King]

Edison invented the electric chair to demonstrate how dangerous AC was. This was after he electrocuted an Elephant in a public spectacle to show how you should only use nice safe dc. Which he just happend to have the patents on. While he had no rights to ac power.
Bil lD
It didn’t go well when the attempt to kill the elephant failed. The electrical shock wounded him and he was suffering so they shot him.

[Stan Coryell]

I don't think anyone who competed with Edison had an easy life. To confuse things more, some old machines, particularly from the Northeast have old two phase motors or 200v three phase. A vfd handles the 200v but nothing really handles the two phase very well. Dave

I've never run across 200 vac. Plenty of 208 vac 3 phase.

2 phase was common in Philadelphia, Camden, and Niagara Falls (so I've heard). I can only speak of Philadelphia. There is still quite a bit of it. Most of the industry is gone, but it's still common for elevators. Which are costly to convert for a number of reasons.

PECO's 2 phase distribution is 4Kv. It's fed from a 3 phase 13.2 Kv transformer that steps it down to 2 phase 4 Kv. I've read somewhere that the idea of 2 phase, was to parallel 2 single phase circuits. In the teens an 20's when DC and single phase generation bit the dust, there must have been quite a bit of two phase already in use. For what ever reason PECO has resisted changing it over until recently. Mostly because of 100 year old 4 Kv distribution cable failures. Also, a lot of the 4Kv equipment was installed just after WW2. Maintenance and replacement parts are now astronomical.

I worked for a shop, starting in 2000. One of the newer presses was about 1965. It was factory wired from Cincinnati 220 VAC 2 phase, 4 wire (two neutrals). That's the newest machine I've run across wired for 2 phase.

To the OP:
A lot of people use 220 and 240 interchangeably. Myself included. However, in the global economy, 220 vac single phase is sometimes associated with 50 hz (220 phase to ground). We have a few presses that have 240 v to 220 v transformers in them. AC motors run at lower speed on 50hz. Here in the US we use 60 Hz. This lower speed may cause overheating issues. Unlikely with a table saw.

[Bill Dufour]

Yes Tesla invented ac motors and had the patent against Edison's dc motor. AC has transformers allowing higher distribution voltage which are much smaller and more efficient use of metal.
Tesla Motors has no relation to N. Tesla and family except they stole his name. I believe the company donated some money to the Tesla museum. There is a small powerhouse on the truckee river in the Sierra Nevada named Tesla.
Bil lD

[Rob Damon]

Typical Residential is 120/240v single phase because you are taking the 240v off the pole/ground mounted transformer and tying to the middle of the 240v winding to getting two legs of 120v to gnd. You will see a single transformer on the pole or ground. This 120 volt generally range from 108v to 132v and the 240v can range from 216v to 250v. But they generally try to hit the median voltage.

Small businesses that are generally located in rural residential areas that does not have 3 phase overhead lines will have sometimes 120/240v 3 phase. You use A/B/C legs to get 3 phase and use A or C legs to get 120v but you can't use the center (high) leg to get 120v (you generally get a 277v you can't use.) You will see two transformers on the pole, as small one and a larger one.

Small and Large business in commercial areas with 3 high voltage overhead lines will give you either 120/208v, 3 phase or 277/480v, 3 phase. You will see 3 transformers of equal size on a pole or a larger ground mounted transformer.

For motor loads you will see nameplates that may say 200v which will run on 208v system. Sometimes the name plate will say 200v - 230v which means it will run on 208v or 240v. Most will be on 208v even though the measure range from the transformer can be 10% above/below that voltage.

Most service transformers have taps so if the measured voltage is really low or really high, the utility can connect to a higher or lower tap on the transformer to adjust the voltage to feed your building or if the service conductors run to a transformer that is far from the building to account for voltage drop.

This also holds true for the 480v system, you will see some motors listed as 440V, 460V and maybe 480v but most are labeled 460V. This is for just the US.

I have seen an odd machine that may have an odd voltage and that's when special transformer come into play to adjust the voltage to suite the machine.

[Jason Roehl]

The building in which I am the maintenance tech uses pneumatic HVAC controls, so I have a large two-motor/two-pump compressor to supply the pneumatic system. At one point we had to replace both motors because a contactor failed, causing the motors to run continuously—one was still running, on fire, when my co-worker discovered it. Anyway, the replacements we found for it were 200V—made for continuous duty on a 208V 3-phase system (what my building is). Upon a further online search, 200V is a standard nameplate rating for a 3-phase motor intended to run on a 208V system.

[Alan Lightstone]

And let's not forget JP Morgan funding Edison in the fight against Westinghouse, and Tesla.

Now why are 3 phase systems 208V? Is it because the amplitude of the voltage difference between two phases is sqrt3 times the amplitude of the voltage of the individual phases (120x1.73)? Or some other reason a standard was chosen.

Looking back, it was amazing that I wasn't taught a thing about electrical distribution in lower level electricity and magnetism courses at MIT. But I still can recite Maxwell's Equations. I guess they saved that for the true EEs.

And how do you tell looking at a utility pole what service is being provided, or available?

[John K Jordan]

...
Now why are 3 phase systems 208V? ...

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.

[Rod Sheridan]

And DC is likely to replace AC for the large high voltage distribution lines. Less loses with DC & modern low cost electronics needed to change the voltage is removing the high infrastructure cost barrier.

Agreed, however probably only for insulated cables, such as submarine applications....Rod

[Steve Demuth]

In school they taught us 1 + 1 is 2. So 110 +110 is 220 so much for that lesson :)

The electrical voltage standard is reducing a very complex energy delivery problem to a single number. Some details necessarily get fuzzy when you do that.

The standard in North America is that the RMS voltage at the service be between 114 and 126 volts, service to ground. That's 120 volts plus or minus 5%. The voltage drop across your motor is supposed to be between about 108 volts and 124 volts.

That's an "average" voltage in the sense that the actual voltage is cycling as a sine curve 60 times per second between a positive maximum with respect to ground, to a negative minimum with respect to ground, and back to the positive maximum. The 120V nominal is the root mean square (RMS) average of that cycle. 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. The RMS voltage is used because for a sinusoidal AC voltage, it represents the DC voltage that would provide the same power as the measured AC voltage. That is, a standard North American 120V AC circuit at some defined current flow, delivers the same power as a DC 120V system at that same current flow.

You get 240 V in North America by taking the voltage across two 120V "legs" that are in precisely opposite phase - so one is at their maximum positive with respect to ground when the other is at their maximum negative. That doubles the voltage difference at every point in the curve, and yields the 120V RMS +120V RMS = 240V.

But if you take two "legs" that aren't in exact phase (from a 3 phase system), the voltages don't double, because the second leg is not at it's negative minimum when the first is at it's positive maximum, but somewhere between ground and its negative minimum. When you do the math, that makes 120V RMS + 120V RMS add up to 208V RMS.

It works this way for standard low voltage delivery systems pretty much everywhere in Canada, the United States, and Mexico. Outside that region, it can be quite different. Japan has two different frequency standards in the same country, requiring essentially separate grids in the East of the country and the West, and runs at 100V RMS, instead of our 120V RMS e.g.

[Mike Henderson]

Agreed, however probably only for insulated cables, such as submarine applications....Rod

I don't think that's correct Rod. There are a number of terrestrial high voltage DC transmission lines. One advantage of DC is lack of skin effect. Also good for transmission between grids that are not synchronized to each other.

Mike

Wikipedia has a good article here (https://en.wikipedia.org/wiki/High-voltage_direct_current).

[Frank Pratt]

Agreed, however probably only for insulated cables, such as submarine applications....Rod

Overhead too. There's an 800 kM, 500 kV, 1500 mW DC transmission line in India, China has an 1100 kV line that's 3300 kM. There's an intersting read on the subject in Wikipedia: https://en.wikipedia.org/wiki/High-voltage_direct_current

Oops, Mike beat me to the link.

[Wes Grass]

Unless it”$ three phase, then 120 + 120 = 208:D


Regards, Rod


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.

[Steve Demuth]

I don't think that's correct Rod. There are a number of terrestrial high voltage DC transmission lines. One advantage of DC is lack of skin effect. Also good for transmission between grids that are not synchronized to each other.

Mike

Wikipedia has a good article here (https://en.wikipedia.org/wiki/High-voltage_direct_current).

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.

[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-drop-calculator.html?material=copper&wiresize=5.211&voltage=120&phase=ac&noofconductor=1&distance=50&distanceunit=feet&amperes=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-drop-calculator.html?material=copper&wiresize=5.211&voltage=120&phase=ac&noofconductor=1&distance=50&distanceunit=feet&amperes=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.


451474 451475

[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.

[Frank Pratt]

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?

High voltage is the key to reducing losses in transmission. Back in the day, there was no easy, economical way to boost DC to a higher voltage for transmission & than back down to a safer voltage for consumer use. AC used simple transformers to do that. That's why AC won out in for utility distribution.

[Stan Coryell]

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.


451474 451475

In the second picture, the wire that looks like it burned the pole is a ground. It goes to the Lighting Arrestor, H1 is tied to the LA's primary. If there is a lighting strike on the primary, the LA bleeds it to ground before it gets to the transformer. It's sort of a big spark plug. Why it flashed to the pole is anyone's guess.

[Bruce King]

451506451507
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.

I tested a 20 amp circuit, 12 gauge wire, about 50 feet using the third/last receptacle in the run.
120.2 volts with no load
added an 18 amp load
116.5 with 18 amps.
About a 3 percent voltage drop.

[John K Jordan]

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.

Many single phase AC motors will run on somewhat lower voltage. The potential problem is, they will then draw more current to generate the same output power. A little of this is usually not a problem unless the voltage is so low that the current it draws is so high the feed wires and motor windings also overheat. (Heated wires have higher resistance which further reduces the voltage making things worse.) At some point the motor is damaged. This can happen from a voltage drop from a wire that is too long.

Many years ago my brother-in-law burned up three motors by running 110v through long wires to the pump in his spring. Instead of running a larger wire, he solved the problem by supplying 220 volts and switching the new motor to run on 220v instead of 110, cutting the current draw in half. He never burned up another pump motor.

I don't know how this applied to 3-phase motors driven by a VFD.

JKJ

[Mike Henderson]

451506451507

I tested a 20 amp circuit, 12 gauge wire, about 50 feet using the third/last receptacle in the run.
120.2 volts with no load
added an 18 amp load
116.5 with 18 amps.
About a 3 percent voltage drop.

It would be interesting to run that same test on the closest outlet - with the shortest wire run - and see what drop you get.

Mike

[Bruce King]

It would be interesting to run that same test on the closest outlet - with the shortest wire run - and see what drop you get.
Mike

With good connections it’s all going to be pretty close to this calculator. The length of the wire is not always known if it’s behind drywall.
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=5.211&voltage=120&phase=ac&noofconductor=1&distance=50&distanceunit=feet&amperes=15&x=63&y=27

[Doug Dawson]

451506451507

I tested a 20 amp circuit, 12 gauge wire, about 50 feet using the third/last receptacle in the run.
120.2 volts with no load
added an 18 amp load
116.5 with 18 amps.
About a 3 percent voltage drop.
That’s not a load tester.

Over the past five years I’ve checked out over a hundred homes with mine, and the voltage drop is typically in the 3 to 7 percent range with a 15amp load, with some variation outside of that. That’s an observed reality.

Most of this was while looking for a new home that I would be satisfied with, given that I’m very particular about some stuff (that might touch on electrical, which would inevitably require some modifications.) Finally found one, BTW.

[Jim Becker]

I had to put a buck/boost transformer on my slider because for a time period the voltage from the street was either too high or too low...I don't recall at this point and it was tripping the circuitry that monitored for that. The saw would just stop working until I did the labor to get inside and reset things. My point here is that some tools are designed to support a very specific range of voltage fluctuation and if the "line steps over the line"...you get no sawdust. Sam Blasco helped me diagnose that back when it happened. The power company later found a degrading transformer feeding our property and rectified it.

[Bruce King]

That’s not a load tester.

Over the past five years I’ve checked out over a hundred homes with mine, and the voltage drop is typically in the 3 to 7 percent range with a 15amp load, with some variation outside of that. That’s an observed reality.

Most of this was while looking for a new home that I would be satisfied with, given that I’m very particular about some stuff (that might touch on electrical, which would inevitably require some modifications.) Finally found one, BTW.

That’s a current meter. I also had a load and a volt meter. Your load tester combines all that in one tool. My measurements and technique is perfect and agrees with published data. Your load tester is probably using a higher load than the 15 amps you posted or the cable length is very long or loose connections.

[Mike Henderson]

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?

The major reason back then was that AC voltage could be stepped up and stepped down with a simple transformer. So you could step up the voltage to a very high level for long distance transmission and then step it down to a voltage for local transmission and finally to residential voltage.

You couldn't do that with DC back in the early days so DC had to be carried at the user voltage level which implied very high currents and high losses.

Today, we have the technology to convert between AC and DC at a reasonable cost and efficiency so DC can be used for long distance transmission at very high voltage levels.

Mike

[Doug Dawson]

That’s a current meter. I also had a load and a volt meter. Your load tester combines all that in one tool. My measurements and technique is perfect and agrees with published data. Your load tester is probably using a higher load than the 15 amps you posted or the cable length is very long or loose connections.

I have both the Extech and the Ideal SureTest, and they’re consistent with one another. (The Ideal is good for bootleg grounds, but I prefer the Extech because it plays nice with AFCI.) It sounds like you’ve got a lot of connections there, and a few data points. I have many more data points, across a broad range of structures. You seem to be indicting the whole of the residential wiring trade, across many decades. :^)

Anyway, the point is that what appears at the receptacle is not always what you think it should be.

[Andy D Jones]

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?

AC or DC, very high voltage (and proportionally less current) always has an advantage in long distance power transmission lines. The lower the voltage, the higher the current (and vice versa), and resistance losses in transmission lines are proportional to current, not voltage.

The early advantages of AC over DC had to do with the difficulty (= cost), in that era, of efficiently changing DC voltages, compared to using a simple transformer to change AC voltage. Since DC voltage could not easily be raised for efficient transmission voltages (or reduced for safe consumption at the end users), transmitting it over long distances was cost-prohibitive.

Modern electronics have drastically reduced the cost of changing DC voltages at very high power levels, though only enough to make long distance DC transmission more cost effective overall. It is still cheaper to change AC voltages with a transformer, especially at high power, but when the combined conversion and transmission costs are considered, DC now wins for very high power and/or very long distance applications.

As an illustration of the relentless pursuit of efficiency, high power generator armatures are spun in hydrogen atmospheres, to reduce mechanical resistance losses. Helium, while advantageously inert, would have twice the viscosity of hydrogen. A vacuum is not practical because of the lack of an insulating atmosphere (electrons at the potential in these generators can fly around rather easily in a vacuum.) So they just have to make sure there is no oxygen mixed in with the hydrogen. At those power levels, even small percentage losses are still big losses, and seemingly extreme measures are cost-effective.

-- Andy - Arlington TX

[Steve Demuth]

As an illustration of the relentless pursuit of efficiency, high power generator armatures are spun in hydrogen atmospheres, to reduce mechanical resistance losses. Helium, while advantageously inert, would have twice the viscosity of hydrogen. A vacuum is not practical because of the lack of an insulating atmosphere (electrons at the potential in these generators can fly around rather easily in a vacuum.) So they just have to make sure there is no oxygen mixed in with the hydrogen. At those power levels, even small percentage losses are still big losses, and seemingly extreme measures are cost-effective.

-- Andy - Arlington TX

Hydrogen atmosphere is used in large dynamos to cool the windings, not to insulate them. There is no practical difference in the electrical insulating effect of hydrogen vs air vs vacuum - the hydrogen being only .025% more dielectric than a vacuum. Hydrogen is, however, a significantly more efficient thermal medium than either air (or Helium) - easier to move with fans, and much better thermal conductivity. That's why it's used to cool dynamos.

[Tony Shea]

Hydrogen atmosphere is used in large dynamos to cool the windings, not to insulate them. There is no practical difference in the electrical insulating effect of hydrogen vs air vs vacuum - the hydrogen being only .025% more dielectric than a vacuum. Hydrogen is, however, a significantly more efficient thermal medium than either air (or Helium) - easier to move with fans, and much better thermal conductivity. That's why it's used to cool dynamos.


You both are correct BTW!! Andy is not necessarily correct about the insulating properties of hydrogen but one of the reasons it's used is definitely because of the viscosity of the gas not just the efficiency of it's thermal conductivity. There is much less drag in hydrogen than in air therefore Andy is correct in that there is much less mechanical resistance! But Steve is also correct in that hydrogen is much better at dissipating heat.

[Mike Cutler]

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?

Jeff
I don't know if you're still keeping track of your post, but after 4 pages of academic discussion the simple answer is, yes, treat them the same, as long as you live in the continental US.

[jeff friedman]

Got it . Thanks

[Bill Dufour]

As a kid I was surprised that a lot of the war surplus ac motors were 400HZ. My Dad explanied that the higher frequency meant smaller and lighter weight transformers and motor coils.
High power transmission lines use dc now that it is much less expensive to switch ac/dc both ways. DC has almost no wasted energy by switching polarity and energizing all the nearby metal like the metal towers. this reduces energy lost to heating nearby conductive objects.
Bil lD

[John K Jordan]

... DC has almost no wasted energy by switching polarity and energizing all the nearby metal like the metal towers. this reduces energy lost to heating nearby conductive objects.
Bil lD

I once set up my telescope under some high power AC transmission lines. I was surprised at the odd feel when I ran my hand down the chrome legs of the scope tripod. Looking closer, there were tiny discharge arcs all around the tripod leg between the metal and my skin. Not enough to shock but definitely enough to see and feel!

JKJ

[Bill Dufour]

I learned in high school that you do normally get killed by touching a high voltage wire and getting sparked. instead you are on a metal ladder that gets near to the wires and it generates a voltage in the metal which is what actually zaps you. Birds are nowhere near ground potential so they can touch one wire at a time safely.
There are laws that outlaw runing wires under high voltage line sand generating power from the radiated emf fields.
Bil lD

Spark gap voltage is roughly 30,000 volts per centimeter in dry air. So a 120 kv spark is only 4cm long

[John K Jordan]

...
Spark gap voltage is roughly 30,000 volts per centimeter in dry air. So a 120 kv spark is only 4cm long

FWIW, the sparking/arcing I saw and experienced with my fingers all the way around the telescope tripod legs was way less then 1 mm in length.

The discharge voltage also apparently depends on the shape of the electrode. My buddy and I built a Van De Graaff generator that let him get continuous 11" arcs from the tip of a finger. Nice party trick when he used the tip of his tongue. Calculate that voltage Low current, though.

In a darkened room I could detect dimly visible continuous electron "spray" at the point of a pin held in my fingers feet away when approaching the globe of the generator.

Approach it with a broader part of the body, such as the side of the forearm, and you would get a single strong, bright, painful lightning zap from maybe 3-4" away. The less brave could hold a sphere or approach with the bottom of a metal bowl. The lack of the pointed "electrode" apparently allowed the generator to hold onto its charge longer then release it all at once.

JKJ