Anyone Else Outraged About 3 Phase?

[CatalinaWOW]

I can't argue with your desire to use your Euro equipment.  But why swim upstream?  While you and many others have no respect for the US standard 110V 15A and 20A outlets, there are other options which comply with local codes and meet your needs and might even get your approval.  Buying or building a set of inline adapters so you don't have to change the power cords on your equipment would leave your home compliant with local codes, much easier to sell and probably not any more expensive than the wiring job you propose.

It would be just as pointless for an American (comfortable with the standards he was used to) to rewire a European home to American standards. 

[HobGoblyn]

Usually 3 phase is delivered to a substation that splits the single phases to different streets. It does not make economic sense to put all 3 phases down every street just in case one person wants it as it adds to the cabling required. No point in the OP going frantic. You want an industrial power supply? move to an industrial location.

I think you'll find that pretty much all of UK residential streets have a 3-phase supply running along them, whether they're above ground or buried. The odd exception might be a tiny rural group of houses that only justifies a single phase pole mounted transformer.

Buried street cables are 3 phase (and neutral outer sheath) with 2-3 adjacent houses tapped off each phase to balance the load. Ours is on the yellow phase (old colour coding convention).

Over the years there’s been a few power cuts where I live (including one where the pavement blew up outside neighbours house) and in all but the last one, the whole street was out.

Last one was funny to see, it happened early evening, when dark.

My house, neighbour to the right had no power, neighbour to the left had power. Shop 30 yards away had to close as it lost 1/2 its power.  And looking down the street, it was an unusual sight  (for me) seeing a few houses with power then a few without etc

[tautech]

Last one was funny to see, it happened early evening, when dark.

My house, neighbour to the right had no power, neighbour to the left had power. Shop 30 yards away had to close as it lost 1/2 its power.  And looking down the street, it was an unusual sight  (for me) seeing a few houses with power then a few without etc

These are not unusual when one phase of the HV supply drops out and the effect on the end user depends entirely on which phase feeds them when fed with a single phase supply.
Lights dim greatly and can go out completely if additional loads are added to the mains.

In the past when confused about what was happening the Fluke measured from ~70-120VAC whereas we're normally 235VAC. Mad panic ensues as we rush around turning OFF any load that could possibly be damaged by such low voltages and special attention is paid to any 3ph loads fed from our other 3ph supply that might automatically turn ON while only 2 phases are active. 
Phase failure protection relays have now been added to such loads. 

[David Hess]

I had a tree limb take down the line from the power line to the house a few years ago which only resulted in breaking the neutral.  Since it was going to take a few days for the power company to repair, I used my massive 240 volt AC phase splitter to regenerate the neutral connection for the whole house preserving balance between the 120 volt AC phases.

I tried including a picture but the forum is not accepting it.

"Your attachment has failed security checks and cannot be uploaded. Please consult the forum administrator."

[CatalinaWOW]

I had a tree limb take down the line from the power line to the house a few years ago which only resulted in breaking the neutral.  Since it was going to take a few days for the power company to repair, I used my massive 240 volt AC phase splitter to regenerate the neutral connection for the whole house preserving balance between the 120 volt AC phases.

I tried including a picture but the forum is not accepting it.

"Your attachment has failed security checks and cannot be uploaded. Please consult the forum administrator."

This problem has hit a few people.  The administrators don't know what the problem is.  Pasting pictures in a .pdf document is one way around it.

[Yansi]

Usually 3 phase is delivered to a substation that splits the single phases to different streets. It does not make economic sense to put all 3 phases down every street just in case one person wants it as it adds to the cabling required. No point in the OP going frantic. You want an industrial power supply? move to an industrial location.

That is not unfortunately the full truth.

Calculate how much power you can transfer with a single phase using amount X of copper. Then calculate same, using the same amount X of copper split for three phases.

As what you said, is a mathematically proven nonsense. Also, having separate loads on each phase create load imbalances and a lot more issues and stupid inconveniences.

I don't understand what you're getting at there....  Could you elaborate a little, please?

Three phase distribution can move 2-times more power per same amount of copper in the lines.

With that american split-phase thing, it is even more times.

That's why it's more then enough for a EUropean houshold to have just a 3x20 or 3x25A breaker panel. Even that is hell of a lot. (17 kW).

[Zucca]

your insurance companies will not pay you anything, and if someone gets hurt or worse, you will be sued within an inch of your life. Or, if you ever plan to sell your house, the modified wiring system will be a huge liability.

I was expecting that in the first response, finally...
I know. When I was in US I had already done that. It would be a smart thing, so I will turn it into normal US home in 5 minutes.
Regarding safety it will be more safe than a normal US home, trust me.
As long I am safe, I will sleep well at night.

You should see the moving company last time when I was going back to EU. The last thing they packed was the screw driver after I relocated the wires in the main grid panel.
It was funny.

[Siwastaja]

Note that the complete analysis of how AC induction motor works fundamentally changes if driven off mains vs. with VFD. The whole point of the VFD is to monitor the motor state and work it in optimal conditions (simplified: with optimal slip). When run off mains, running the motor in (nearly) optimal conditions happens only in very lucky (or very well engineered!) cases, namely if the load happens to be just right for the motor and the load torque is not varying (except for very short times, during which we just decide it doesn't matter).

Real-world off-mains usage of 3-phase motors requires special considerations like soft-starting, delta-wye switching, power factor correction etc. etc., which all become off-topic when driving with VFD. This is not even to mention mechanical gearboxes, gear switching, clutches, belts and whatnot used to deliver torque far from the optimal rpm (synchronous frequency minus slip).

Off-mains motors may be even designed to provide somewhat better performance far below the optimal slip, compromising the efficiency at optimal slip. Such compromised motor would be a wasted effort when driven on VFD.

[Zucca]

Yep 50Hz or 60Hz doesn't really matter for a motor.

Even for a single phase motor with a starting cap? I mean a 1/j2pi*f*C cap@50Hz != cap@60Hz , or event the magnetic flux in the motor windings will be different in amplitude, not just in frequency.
Or the difference is not noticeable in real life? Sorry if it was a stupid question, I just have some university memories about motors.

[m k]

What is worse, high or low voltage?
Can't remember what regular gadgets have most but least is many times under 200.
Here voltage is already lifted twice but can't remember any fuss around them.
Only argument I can remember was around 0-class and schuko wall outlets.

Here original single phase contract is probably around 50 years old minimum.
That is also truly single, means phase to ground and probably 20A or so.

Disadvantage here can be the length of a user line.
Rural last drop has many times been one drop only from middle voltage grid so distribution point can be guite far.
Not very optimal if you are a summer cottager after say a dairy farm or two.
On the other hand, around here summer nights are short and solar panels affordable.

What about a stove clock then.
With 3-phases the clock can stay one no matter how lightning is flicking the lights.

[Berni]

Yep 50Hz or 60Hz doesn't really matter for a motor.

Even for a single phase motor with a starting cap? I mean a 1/j2pi*f*C cap@50Hz != cap@60Hz , or event the magnetic flux in the motor windings will be different in amplitude, not just in frequency.
Or the difference is not noticeable in real life? Sorry if it was a stupid question, I just have some university memories about motors.

Technically yes it does change the shift, but the motors don't care that much about it being spot on, it just needs something in the ballpark of the correct phase shift so that it can create torque at standstill so that it can start up. The capacitor contributes very little to the total torque once the motor is running at nominal speed. In fact some single phase motors use it only for start and then disconnect it using a centrifugal switch, this lets them under-spec the starting windings with thinner copper since they only need to work for a few seconds, they can put the extra copper to better use by giving it thicker main windings as those produce the power, at the same time optimizing the starting windings to give more torque at a standstill. Remember the phase shift on the capacitor can also change as the real and reactive power move around on the motor winding under different running conditions.

This is also why the starting torque on single phase async motors is so poor. They like having easy to start loads like fans or saws. The 3 phase async motor is quite a bit better at starting torque since it has those extra proper full power phases at its disposal, but at the same time this creates startup problems on the power supply side since async motors are horribly efficient once slip gets too high, so when they try to produce so much torque they draw an insane amount of current. This is typically solved by a delta/star starting switch since running in star makes the motor see less voltage so it draws less current, once its up to speed its switched to delta for full power at full voltage. Its a pretty cheap solution since motors with a manual on/off switch can simply replace it with a 3 position switch that goes OFF/Star/Delta and the operator simply leaves it in Star for a few seconds before switching to Delta. Power factor correction and such is not a big issue, a factory simply has a centralized power factor correction bank at the transformer that switches in caps across the supply to correct the inductive reactive power from motors in the whole factory. The speed of the motor is not a problem as long as you always need it to run at the same speed, just simply chose a motor with the correct number of poles for the speed you need, more poles, closer together the electromagnets are so 50Hz takes longer to get around so the motor spins slower and produces more torque. Over-specing a 3 phase motor is not that bad either, it still runs pretty efficient with a too light load, its efficiency just drops off a cliff once you overload it (causing the slip to get too big, causing speed to drop, slip increase even more...etc)

But yes the modern solution to all that is simply a VFD. Just flick a switch and the VFD will slowly bring up the voltage and frequency to gently soft start the motor and give it even more torque since the frequency is matched to the speed so that its operating in an efficient regime all trough the startup ramp. Also the sort of machines that big motors run in the home shop tend to benefit from speed control. Having a simple speed dial on your mill, lathe, drillpress, grinder, bandsaw etc... is nice to have.

[Alti]

Three phase distribution can move 2-times more power per same amount of copper in the lines.

Three phase four conductor is generally more Cu efficient and at the same time it has sqrt3 higher voltage so it is a bit like comparing apples and oranges as different ratings of cables are needed. And same rating cable with 230V withstands more abuse than with 400V. But I must agree, sheath does not count as Cu cost.

That was cable-wise. As for the safety-wise, three phase is a compromise in between high'er power and low'er voltage. You can have both from four wires. That is why three phase is a sweet spot. Had you increased single phase to 400V, Cu-wise this would have been a tad cheaper than 4 conductor three phase 230V/400V.

[Zucca]

Thanks Berni, I appreciate your patience to write down this good explanation.

[Yansi]

Three phase distribution can move 2-times more power per same amount of copper in the lines.

Three phase four conductor is generally more Cu efficient and at the same time it has sqrt3 higher voltage so it is a bit like comparing apples and oranges as different ratings of cables are needed. And same rating cable with 230V withstands more abuse than with 400V. But I must agree, sheath does not count as Cu cost.

That was cable-wise. As for the safety-wise, three phase is a compromise in between high'er power and low'er voltage. You can have both from four wires. That is why three phase is a sweet spot. Had you increased single phase to 400V, Cu-wise this would have been a tad cheaper than 4 conductor three phase 230V/400V.

Cable rating is exactly the same 300/500V, which means Uo/U (against ground/against each other).  Same rated cables used everywhere, even for single phase stuff.

Hence I find your complaint void. No difference buying a cable for single phase, or three phase application - with the exception of some household flexible cords, the thin stuff, that is just 300/300 rated.  Some "high power" low voltage cables are rated 500/700V, because at times, we use even higher voltages than 230/400V. For example, if I am not mistaken, mines run at 500V 3ph ac and some application use even higher voltages such as 690V.

This is standardized across the whole EU.  Look for H03, H05 H07 type of wires/cables. I think it is in IEC 60227-3.

[james_s]

Usually 3 phase is delivered to a substation that splits the single phases to different streets. It does not make economic sense to put all 3 phases down every street just in case one person wants it as it adds to the cabling required. No point in the OP going frantic. You want an industrial power supply? move to an industrial location.

That is not unfortunately the full truth.

Calculate how much power you can transfer with a single phase using amount X of copper. Then calculate same, using the same amount X of copper split for three phases.

As what you said, is a mathematically proven nonsense. Also, having separate loads on each phase create load imbalances and a lot more issues and stupid inconveniences.

I don't understand what you're getting at there....  Could you elaborate a little, please?

Three phase distribution can move 2-times more power per same amount of copper in the lines.

With that american split-phase thing, it is even more times.

That's why it's more then enough for a EUropean houshold to have just a 3x20 or 3x25A breaker panel. Even that is hell of a lot. (17 kW).

But we have 3 phase distribution here too, it's just not used for the last hundred feet or so, or the last couple miles in some cases where a more rural area is fed by only one of the phases. 17kVA would be considered grossly inadequate for typical US homes, the minimum standard is 200A 240V which is 48kVA. Looking at just the major loads in a typical home, 5.5kW clothes dryer, 2-3kW A/C, oven and cooktop 4-10kW, then if the house doesn't have gas, a hot water heater will be typically 4.4kW, electric heat pump 3-5kW, if they have electric resistance heat which was once widespread that can be 15-20kW just for the heating. I have natural gas for my heating, hot water and cooking but my hot tub is electric and pulls over 10kW when in use with both pumps and the heating on. Very little would change if I had 3 phase to my house, instead of 2x200A main it would be maybe 3x125A, and my house is not large or fancy by American standards.

[Siwastaja]

Yes it's kinda funny how a "typical" American house wiring is just single phase yet supply significantly more power than our typical European 3-phase house installation.

Yes, unsurprisingly, 1x200A is more than 3x25A or 3x35A.

Actually, we do have to think about balancing loads between phases which is an extra task and not always trivial, so 3x25A is actually somewhat less than 1x75A. Not much so, because largest loads are heaters connected in wye or delta with good balancing, but anyway.

The only thing our 3-phase house wiring really shines if you want to drive 3-phase motors directly off the mains. But that's quite a rarity anyway in households; small motors in household appliances are either brushed, or cap start / cap run.

We here seem to assume the USA is living in the stone age with their single-phase / split phase wiring, but that is obviously not true despite power systems being different. The cultural difference seems to be having higher power appliances available, yet here we concentrate on laughing at the 110V 15A plug and its incapability of delivering power, yet the real typical US cooktop is easily around some 10kW, something we won't see here at all.

[langwadt]

Yes it's kinda funny how a "typical" American house wiring is just single phase yet supply significantly more power than our typical European 3-phase house installation.

Yes, unsurprisingly, 1x200A is more than 3x25A or 3x35A.

Actually, we do have to think about balancing loads between phases which is an extra task and not always trivial, so 3x25A is actually somewhat less than 1x75A. Not much so, because largest loads are heaters connected in wye or delta with good balancing, but anyway.

The only thing our 3-phase house wiring really shines if you want to drive 3-phase motors directly off the mains. But that's quite a rarity anyway in households; small motors in household appliances are either brushed, or cap start / cap run.

We here seem to assume the USA is living in the stone age with their single-phase / split phase wiring, but that is obviously not true despite power systems being different. The cultural difference seems to be having higher power appliances available, yet here we concentrate on laughing at the 110V 15A plug and its incapability of delivering power, yet the real typical US cooktop is easily around some 10kW, something we won't see here at all.

looking at a few random stoves here and US they all seem to be around 10-11kW for four "burners" and an oven

[madires]

What about a stove clock then.
With 3-phases the clock can stay one no matter how lightning is flicking the lights.

All household ovens/stoves I've seen over here are built for Y/star wiring, i.e. phases to neutral. So the clock is powered only by one phase. The usual arrangement is one phase for the oven (including the clock) and two for the cooking plates. Breakers are 16A, so you can have 3 * 16A * 230V = 11kW at maximum.

[Berni]

Yep here also all the ovens come with a 3 phase terminal block in the back to be able to spread the load over those phases. and 16A per phase is pretty typical of most large appliances. If you don't have 3 phase then you just wire all of them to the same phase. Induction cookers do a similar thing where they are built with 3 phase input, tho i have seen some weird 2 phase input on those too, it could get enough power from 2x16A so it just skips the third phase.

The supplemental electric heater used with our heatpump also is also 3 phase by simply having 3 separate heating elements to spread the load, much like the oven has multiple elements. But this is only a backup for cases where it might get really really cold and the heatpump might not keep up. Heating houses directly from electricity is never done here because its way too expensive. Maybe the US has so much cheaper power that it does not matter? Or is that only done in places where the winter never gets very cold? Power is about 6 euro cents per kW/h so heating a decent sized house would probably cost you like 1 grand per month.

[madires]

EUR 0.06 per kWh? Wow! We have to pay EUR 0.30 and more (average price might be around 0.33).

[BlackICE]

In the state of California in the USA all the eco policies have progressively tiered pricing where many larger homes have a marginal rate at about $0.5 to more then $0.7 at KW/hr!  Even the state of Hawaii has lower rates than CA.

The supply doesn't exist so they limit demand by having the highest prices most anywhere in the industrial world! People just suck it up and limit their use or pay the piper.

[Berni]

Wow half a dollar for a kW/h? How much is the typical power bill per month then if houses are so power hungry to need a 200A service.  Like a household spending >10 grand per year just on electricity?

Over here it costs up to 300€ in the cold winter months when a lot of power is used by the heatpump for heating, while a normal power bill tends to be under 100€.

[JohnG]

I believe the key is "progressively tiered", so the extreme rates are for people with BIG houses. Average rates paid rates are closer to $0.2/(kW*hr). Still expensive.

I don't live in California, but my employer is headquartered there and I visit fairly often (or used to). There are some really rich people in CA who would not even blink at a $10k annual electric bill.

Also, houses don't pull 200A all the time. The duty cycle is pretty low for the majority of people. Where I live, there is one transformer for each 3-5 people. They are not sized to handle all houses at full load for any length of time. I don't recall what the scaling factor is around where I live, though.

John

[JohnG]

On heating appliances like cooktops in the US, they are nominally rated for 240V operation, with three wires, L1, L2, and N (neutral). A higher-end one will pull a peak power of about 10 kW with all hobs on full and the oven going on full as well, i.e. 40A draw. If you look at the label, though, you will see that many have a reduced set of specs for 208V operation. This is because many newer apartments and condos in the US use 3 phase, and sqrt(3)*120v = 208.

On a tangential note, if you apply 120V from one of the lines to the neutral, you will activate "sales demo mode" where all the features and lights turn on, but the heating elements are not activated. It increases sales, or it did when people bought these in stores. Kind of like "store mode" for AV electronics.

John

[james_s]

The supplemental electric heater used with our heatpump also is also 3 phase by simply having 3 separate heating elements to spread the load, much like the oven has multiple elements. But this is only a backup for cases where it might get really really cold and the heatpump might not keep up. Heating houses directly from electricity is never done here because its way too expensive. Maybe the US has so much cheaper power that it does not matter? Or is that only done in places where the winter never gets very cold? Power is about 6 euro cents per kW/h so heating a decent sized house would probably cost you like 1 grand per month.

I pay about 8 cents per kWh which is below the national average today. It used to be much cheaper when I was a kid, we lived in a 2500 sqft house that was all electric originally, heating was a central forced air electric furnace that was probably 20kW. In the mid 80s the subsidy on the hydro plants went away and electricity prices went up quite significantly, then not long after my area got natural gas service and my family upgraded to gas heating and hot water. Even today most apartments have electric resistance heat and hot water, I haven't seen resistance heat used in any newer houses though. This area has a mild climate but still gets cold in the winter, not like the Northern middle parts of the country though.