Using High-Leg Delta for Japanese Appliances?

[winnie]

Ok, so the use case you are describing is to provide both full 240V so generic North American appliances will work properly, and 208V (as an in tolerance substitute for 200V) so that Japanese appliances will work properly.

This is for large high value buildings.

So you are envisioning a large building with 120/240V single phase power for most users, but high leg delta provide 3 phase power for things like elevators, and want to distribute that incidental available 208V to kitchen spaces so that travelers can use high wattage Japanese kitchen appliances.

IMHO thus is a fun hypothetical design, and thinking outside the box is a valuable exercise. I still don't see the value to the end customer.

Seriously:

What Japanese appliances would a traveler bring on a trip which they would want to plug in to a 208V outlet, and which there is no North American substitute?

Wouldn't it be far cheaper, more efficient, and more convenient to locally provide 240V versions of those appliances?

Can you provide a specific example of a Japanese appliance for which there isn't a 240V substitute?

Separate point: Let us presume you provide a use case that justifies 240V and 208V in a single kitchen, and is valuable enough to warrant the necessary non standard wiring and custom transformer banking.

You should also consider custom single phase transformers with multiple secondary taps to provide both 120/240V and 100/200V.

Another custom arrangement worth considering is 'hexaphase' which provides both standard 120/240V and standard 208/120V, presents balanced 3 phase loading to the utility, and makes the 208V a standard L-L voltage.

Both of the above options are not standard. But if you are thinking outside of the box, you shouldn't fixate on a single off the wall idea.

Jon

 

[tortuga]

Japan is the odd country out, both for single-phase and split-phase. If Japan had followed either North American or European/British/Australia standards for premises wiring voltage and frequency, then I wouldn't even have considered using the high-leg to neutral in this hypothetical realistic case.

I have long wondered the history of the 100/200 volt choice in Japan, I have tried to look it up but I don't read Japaneese. I think I have an old thread on here about it. Their HVDC transmission system is interesting.

Another custom arrangement worth considering is 'hexaphase' which provides both standard 120/240V and standard 208/120V, presents balanced 3 phase loading to the utility, and makes the 208V a standard L-L voltage.

Jon have you ever encountered a hexaphase in the wild? I have herd of them on generators but never seen a hexaphase bank.
I have also heard of a transformer that could deliver 240V two and three phase but never seen one.

 

[wwhitney]

makes the 208V a standard L-L voltage.

Does a Japanese 200V appliance require 200V L-N, or is it happy with 200V L-L?

Cheers, Wayne

 

[tortuga]

Does a Japanese 200V appliance require 200V L-N, or is it happy with 200V L-L?

Cheers, Wayne

They are L-L same as here just 100/200 single phase center tap (split phase), and 1/2 are 50 hz half 60 hz.

 

[wwhitney]

They are L-L same as here just 100/200 single phase center tap, and 1/2 are 50 hz half 60 hz.

So then the flip side question for the OP's original idea: Are Japanese 200V appliances OK to use at 200V L-N, or does their design assume or depend on a maximum voltage to ground of 100V? If the latter, scratch the whole idea from the OP.

Cheers, Wayne

 

[tortuga]

So then the flip side question for the OP's original idea: Are Japanese 200V appliances OK to use at 200V L-N, or does their design assume or depend on a maximum voltage to ground of 100V? If the latter, scratch the whole idea from the OP.

Cheers, Wayne

I have a had situation (long ago) where the reverse of that was the problem, the surge protection circuit expected a grounded conductor. It was back when we were upgrading old magnetic ballasts to electronic in florescent fixtures there was a 'multi-volt' ballast that could accept 100-277V but made a pop when connected to '240V' L-L. I have not herd of an issue like that since the early 2000's though. There are old threads about it on here.

 

[winnie]

Jon have you ever encountered a hexaphase in the wild? I have herd of them on generators but never seen a hexaphase bank.

Nope, never seen one in the wild. I have seen hexaphase in textbooks for use with rectifiers. Once I wired a 12 lead motor to a lab inverter in a hexaphase arrangement to get slightly higher coil voltage.

I have also heard of a transformer that could deliver 240V two and three phase but never seen one.

Sounds like a Scott-T transformer type. Those are rare but standard items in places with 2 phase service. They use a high leg to neutral connection and are in some sense a proof of concept for what the OP is suggesting.

Jon

 

[Birken Vogt]

Philadelphia PECO. There was a thread on here or the other site long ago where the OP wound up getting a Scott-T made by Hammond for his job to convert 5 wire 240 volt 2 phase into conventional 3 phase for the whole building. I can't find it any more. Not how I would have done it but it worked.

 

[tortuga]

Sounds like a Scott-T transformer type. Those are rare but standard items in places with 2 phase service. They use a high leg to neutral connection and are in some sense a proof of concept for what the OP is suggesting.

Yeah I have actually seen some two phase stuff in Philly (years ago) along with their scott-T's its very cool, but never this particulare one that took a HV two phase primary side, and delivered both two phase and three phase on the secondary.

 

[00crashtest]

Ok, so the use case you are describing is to provide both full 240V so generic North American appliances will work properly, and 208V (as an in tolerance substitute for 200V) so that Japanese appliances will work properly.

This is for large high value buildings.

So you are envisioning a large building with 120/240V single phase power for most users, but high leg delta provide 3 phase power for things like elevators, and want to distribute that incidental available 208V to kitchen spaces so that travelers can use high wattage Japanese kitchen appliances.

Exactly! However, my wording may have been confusing. By large, I mean the size of the typical low-rise multi-storey office/educational/lodging/multi-family residential building in the suburbs, or a single supermarket or big-box store within a power centre. This obviously excludes groundscrapers such as regional offices of a multi-national company, heavy industrial factories, mass transportation hubs, freight hubs, and regional mailing hubs; the combined floor area of all buildings within giant campuses such as entire power centres, large apartment complexes, colleges, and universities; and skyscrapers.

I only mentioned airport terminals, major intercity train stations, and supertall skyscrapers to illustrate the uniqueness of my building in terms of the electrical system.

For giant buildings such as groundscrapers, skyscrapers, and the combined floor area of giant campuses, it is obviously best to use several three-phase transformers sequentially stepping down the voltages (like what is already done with supplying 208Y/120 from a 480Y/277 in midsized commercial and light industrial buildings, if one were to use a single service), because you get the same high energy efficiency with each set of large three-phase transformer banks despite having multiple ones. However, the typical midsized building has no provision for 240 V and has only relatively small loads, so their relatively small 208Y/120V transformer located within the premises feeder is inefficient. In reality, a typical example of a giant building would probably have more than one service as explicitly allowed by 2020 NEC 230.2(B)(2), (C)(1), and (C)(2). Of course, 230.2(C)(3) and (D) can be applied to a property of any size, but they are only catch-all statements that require special permission because they are specifically addressed by any standard protocols.

Since my proposed building is only large and not giant, it would take a not-insignificant hit in efficiency from having multiple transformers sequentially stepping down the voltage from the power company's distribution lines, which would lead to a not-insignificant increase in CO2 emissions per energy used per branch circuit. It would probably be more efficient (all in terms of instantaneous electrical energy, embodied energy of the hardware, lifetime energy, and lifetime costs) to just use somewhat larger wires for 240V three-phase power in addition to the specifically required 120-, 208-, and 240-volt single-phase power from the same distribution-to-service transformer rather than require another transformer just to get 208Y/120 volts for handheld equipment from a 480Y/277 volt service. If my proposed property had a giant total floor area, then of course I would either
1. have my service points be located at each large-to-midsized zone of the property fed from the utility's specially designed 3-phase 120/240 closed delta transformer banks located within transformer vaults on my property (which seems unlikely that the utility would accept the hassle of dealing with a highly custom design, but I haven't seen how service points are arranged in high-rise condo buildings so I don't know), or
2. have one service point for the entire property running at distribution or subtransmission voltages, and then multiple sets of utility-scale distribution transformers afterwards to each supply the final voltage while ensuring there is only 1 step of conversion from the service point, with each unit having multiple sets of meters and panels, one for each set of voltages.

 

[00crashtest]

What Japanese appliances would a traveler bring on a trip which they would want to plug in to a 208V outlet, and which there is no North American substitute?

None that I can think of, especially given that the US (and particularly Taiwan) already has a sizeable population of people using Japanese-style appliances to enable economies of scale for Japanese manufacturers to produce a special version for 120 and 240 volts respectively, or even economies of scale for domestic manufacturers to produce Japanese-style appliances. However, a traveller from Japan who needs to bring one piece of checked baggage anyway because just a carry-on is not enough but still has plenty of spare room remaining in their checked baggage will still want to bring their own small kitchen appliances, particularly if they come here for a few months every year to an area that doesn't have Japanese-style kitchen appliances for 120 or 240 volts available for sale. Even in an area that sells Japanese appliances for domestic voltage, if they come here for just 1 season every few years for a business trip, particularly if air fare is included, it would be financially wasteful (albeit only a few hundred to a few thousand USD) to buy a set of appliances that is used so rarely. Of course, a regular first-time tourist who comes for only short-term stays of a week or less will certainly not want to bring their own appliances.

Wouldn't it be far cheaper, more efficient, and more convenient to locally provide 240V versions of those appliances?

Yes.

Can you provide a specific example of a Japanese appliance for which there isn't a 240V substitute?

No, because I cannot think of any example.

Separate point: Let us presume you provide a use case that justifies 240V and 208V in a single kitchen, and is valuable enough to warrant the necessary non standard wiring and custom transformer banking.

You should also consider custom single phase transformers with multiple secondary taps to provide both 120/240V and 100/200V.

Yes, I have considered this, but it requires non-standard individual components, which vastly increases parts costs percentage wise. What I'm suggesting requires bog-standard split-phase transformers, only that the overall setup of the three phase bank is highly custom. If that is my property that I am developing I also happen to be the dual-licensed electrician and engineer, then it would cost absolutely nothing for the self-client (me) to do the special calculations for the electrical loads, which only require maths (because spelling in England is the OG for English) as simple as vectors and algebra.

Another custom arrangement worth considering is 'hexaphase' which provides both standard 120/240V and standard 208/120V, presents balanced 3 phase loading to the utility, and makes the 208V a standard L-L voltage.

I didn't know that this existed.

Both of the above options are not standard. But if you are thinking outside of the box, you shouldn't fixate on a single off the wall idea.

Jon

I am fortunately not fixating on a single idea. I am just suggesting using the high-leg to neutral in a 120/240 delta (either closed or open, though closed is highly recommended because it can utilize 100% of the individual transformers' capacities and offers redundancy in supplying three-phase instead of just 86.6% and having no redundancy for three phase) because it seems to be the most efficient, cleanest, easiest, simplest in terms of parts counts, and economical way overall to supply power to personal/household appliances from anywhere globally.

 

[wwhitney]

I am fortunately not fixating on a single idea. I am just suggesting using the high-leg to neutral in a 120/240 delta (either closed or open, though closed is highly recommended because it can utilize 100% of the individual transformers' capacities and offers redundancy in supplying three-phase instead of just 86.6% and having no redundancy for three phase) because it seems to be the most efficient, cleanest, easiest, simplest in terms of parts counts, and economical way overall to supply power to personal/household appliances from anywhere globally.

But the resulting L-G voltage is wrong, it's 208V rather than 100V. Are you sure that all Japanese 200V products have the internal clearances necessitated by 208V to ground?

Cheers, Wayne

 

[synchro]

A 240 to 200V autotransformer would be another option, either single phase or 3-phase. An autotransformer would be significantly more efficient, smaller, and likely cheaper than one with an isolated primary and secondary.
An example of a 240/200V 3-phase autotransformer is at the link below. A range of kVA ratings is available.

Electrical - Transformers - Page 1 - TEMCo Industrial

temcoindustrial.com

 

[LarryFine]

I haven't seen any mention of the multiple, redundant circuits and outlets that would be necessary in places where different voltages would be available.

 

[zbang]

Are you sure that all Japanese 200V products have the internal clearances necessitated by 208V to ground?

I think it would be difficult not to.

 

[00crashtest]

I haven't seen any mention of the multiple, redundant circuits and outlets that would be necessary in places where different voltages would be available.

Each customer of the utility will have their own three-phase meter and panel in this case. This means at least each business, and also each housing unit if there is residential in addition to lodging, will have three phase power that is supplied from the single large transformer common to the property for efficiency purposes. Compared to a standard 120/240V split-phase system, yes there needs to be an extra conductor (2 extra current-carrying conductors because the neutral now is intentionally used in an imbalanced manner), but the energy efficiency gains make the lifetime energy costs lower. In order to reduce the special service charges from the power company for having three phase, the entire building could be a single customer and the billing can just be split by the occupants internally, with the common-area loads being split according to their unit's percentage value of the overall property.

The regular 120/240V split-phase loads will be served by NEMA 14-30, 14-50, and/or hardwired outlets supplied from double pole breakers spanning between phases A and C, and also neutral if it is a GFCI. There will be no straight 240V split-phase circuits with only 2 hots installed because the marginal cost of the extra neutral conductor makes it multiple times more versatile from being able to supply primarily 240V appliances that require 120V for the controls and lights, such as dryers and ovens. The single-phase 208V loads will be served by NEMA 6-20R (because it also accommodates NEMA 6-15P, which consequently accommodates all Japanese split-phase 200V plugs; there are no hardwired appliances at this current and voltage) supplied from single-pole breakers rated 240V or 277 to ground connecting to only phase B, and also neutral if GFCI. If the customer opts for three-phase large appliances that require 240V line-to-line only, then they will be served by NEMA 11-series, NEMA 15-series, and/or hardwired outlets supplied from 3-pole breakers spanning all phases, with the neutral not connected even if GFCI. The regular code-required branch circuits for kitchen small appliances, bathroom small appliances, washing machines, lighting (which cannot exceed 120V line-to-line in residential and lodging units as stated by NEC 210.6(A)), and general-purpose receptacles will be served by NEMA 5-20R (because also accommodates NEMA 5-15P) supplied from at least one single-pole 120V breaker each spanning between phase A and neutral, phase B and neutral, and phase C and neutral in a balanced manner respectively.

This means that there are at least 7 branch circuit required for every unit with a bathroom, kitchen, three-phase 240V branch circuits, and receptacle outlets for 200V Japanese small appliances rated above 1440 VA. At least one split-phase 120/240V circuit will be installed regardless of whether electric large appliances are installed in the unit or not, for the purposes of accommodating European, British, Indian, and Australian non-frequency-sensitive general equipment rated above 1440VA at full power.

 

[00crashtest]

The regular code-required branch circuits for kitchen small appliances, bathroom small appliances, washing machines, lighting (which cannot exceed 120V line-to-line in residential and lodging units as stated by NEC 210.6(A)), and general-purpose receptacles will be served by NEMA 5-20R (because also accommodates NEMA 5-15P) supplied from at least one single-pole 120V breaker each spanning between phase A and neutral, phase B and neutral, and phase C and neutral in a balanced manner respectively.

Oops. Phase B to neutral is not used in this case.

This means that there are at least 7 branch circuit required for every unit with a bathroom, kitchen, three-phase 240V branch circuits, and receptacle outlets for 200V Japanese small appliances rated above 1440 VA. At least one split-phase 120/240V circuit will be installed regardless of whether electric large appliances are installed in the unit or not, for the purposes of accommodating European, British, Indian, and Australian non-frequency-sensitive general equipment rated above 1440VA at full power.

I also did not mention that laundry area was another determining condition.

 

[LarryFine]

What I mean is having to run more than one circuit to any place in the house that might have to accommodate loads from more than one country.

Each outlet would have to be a multi-receptacle panel, looking somewhat like a portable-generator receptacle panel.

 

[00crashtest]

But the resulting L-G voltage is wrong, it's 208V rather than 100V. Are you sure that all Japanese 200V products have the internal clearances necessitated by 208V to ground?

Cheers, Wayne

All Japanese 200V products that don't have a ground pin (of which having no externally exposed conductive parts or being double insulated are a prerequisite) are obviously indirectly designed to work on 200V (consequently 208V because of tolerance) line-to-ground because they do not have any parts at ground potential. That is because even if the electrically floating internally conducting parts were only designed to be insulated against each conductor at 100 volts, 208 volts line-to-ground appearing along one conductor and 0 volts along the other creates electric fields to force the floating conductive internal parts to be in the middle, which means that it only has to withstand a difference of 104 volts relative to each conductor.

For 200V appliances from Japan that have the ground pin, it is risky to plug then into outlets with 208 volts to neutral, unless one has already checked that such appliances have successfully been used on circuits with 208 volts or higher to ground. However, Japan's PSE almost certainly requires all ungrounded current-carrying parts to reliably withstand the line-to-line voltage as line-to-ground [which is the case with premises wiring in the US as required by NEC 110.4 for multi-wire branch circuit conductors in combination with NEC Article 100 Definitions for Voltage (of a circuit)] because it will be incredibly foolish to bond any electrically floating conductive parts on the internal circuit board to the metallic case and grounding conductor rather than insulate them from ground.

Expat and travel forums have shown for decades that plenty of 200V appliances from Japan have successfully been used on continental Europe's 220V 50Hz, and even the UK's, Australia's, and India's 240V 50Hz utility nominal supplies, even though they are all 230V 50Hz nominal for the purposes of equipment design as part of the IEC harmonization process (and indirectly also NEMA, which mainly is to account for voltage drop at motor terminals) to ensure that they can all work at either voltage at full rating.