Why are some stations 208V?

[rolosrevenge]

Why does that ensure the load on each phase stays balanced?

They try really hard to balance the phases when they plan construction. In the US the transmission system is balanced to less than 5% between them. On the distribution system, with split phase transformers tapped off of a single phase the dominant, It's not uncommon to see 20% imbalance between phases. Europe tried more to balance with three phase on their primary and secondary distribution, but their secondary networks run for too far and thus give increased losses. No body really gets it perfect.

 

[ElSupreme]

Why does that ensure the load on each phase stays balanced?

A lot of industrial users get all 3 phases to their facility, and get screamed at and fined by the power company if their usage isn't evenly distributed across the phases. Within some limits of course.

 

[hcsharp]

A couple days ago I was using a ChargePoint at a hotel that was 207v 30A. It's the standard ubiquitous Coulomb unit. Every few seconds the charger flashes across the screen the charging rate of 5790 watts but inside the car it says it's charging at 207v, 30A which is 6200 watts. Why is there a big difference? Sometimes the voltage would drop to 205v but never much lower. Are they using a different method of calculating the watts?

 

[Bipo]

A couple days ago I was using a ChargePoint at a hotel that was 207v 30A. It's the standard ubiquitous Coulomb unit. Every few seconds the charger flashes across the screen the charging rate of 5790 watts but inside the car it says it's charging at 207v, 30A which is 6200 watts. Why is there a big difference? Sometimes the voltage would drop to 205v but never much lower. Are they using a different method of calculating the watts?

Volt·Amp vs. Watt, maybe?? It'd be interesting to know the power factor of that current...

Power factor - Wikipedia, the free encyclopedia

 

[widodh]

And every time you get 208V on an EVSE you can wonder at what might have been if we had adopted the Mennekes (Type 2) connector here in the US which supports 3-phase, instead of the inferior Yazaki J1772 design.

Amen!

Now switch to 230/400V 3-phase power everywhere and you guys finally have a great network

 

[mknox]

Now switch to 230/400V 3-phase power everywhere and you guys finally have a great network

The fact is that N. America already does have 3-phase power everywhere. Transmission is 3-phase, Distribution feeders are 3-phase and secondary 3-phase systems are ubiquitous in commercial and industrial settings. Residences and very small commercial are supplied "single phase" (either split phase 120/240 volts or 2-phases and neutral from a 3-phase system to provide 120/208 volts).

There's no reason from an infrastructure point of view that 3-phase commercial EV charging could not be made available. All of those bemoaning 208 volt single phase chargers out there should be aware that the reason they are getting 208 volts at these stations is because they are single phase EVSE units connected to 2 phases of a 3-phase system that already exists at that location!

 

[RDoc]

@mknox - I was under the impression that 3 phase power wasn't generally available in residential neighborhoods in the US.

 

[widodh]

The fact is that N. America already does have 3-phase power everywhere. Transmission is 3-phase, Distribution feeders are 3-phase and secondary 3-phase systems are ubiquitous in commercial and industrial settings. Residences and very small commercial are supplied "single phase" (either split phase 120/240 volts or 2-phases and neutral from a 3-phase system to provide 120/208 volts).

There's no reason from an infrastructure point of view that 3-phase commercial EV charging could not be made available. All of those bemoaning 208 volt single phase chargers out there should be aware that the reason they are getting 208 volts at these stations is because they are single phase EVSE units connected to 2 phases of a 3-phase system that already exists at that location!

True, but you have so many differences in voltages. 120, 208, 240, 480, 600.

But again, all the EV's are single-phase capable and the J1772 connector doesn't support 3-phase either. So adopt the Type2/Mennekes connector to fix that problem.

 

[mknox]

@mknox - I was under the impression that 3 phase power wasn't generally available in residential neighborhoods in the US.

3-phase Transmission is stepped down to 3-phase distribution level voltages (typically 4 kV to 50 kV depending on the utility and jurisdiction) at transformer stations, and utilities distribute power throughout cities and towns at this level. Typically, 3-phase feeders go almost everywhere and power is stepped down to utilization levels near the home or business. Residential voltages are nominally 120/240 volts, and this can be obtained with a split winding transformer connected to one primary phase and neutral. In residential areas, it is not uncommon to see single phase primary run-offs where one primary phase and a neutral branches off to go down, for instance, a side street or in to an area where there is no demand or requirement for 3-phase power (split winding transformers can be connected to this one phase and neutral to deliver 120/240 volts).

Wherever secondary voltages are 120/208 volts (what we're talking about in this thread), it is because there is a three phase distribution transformer somewhere providing 120/208 volts 3-phase, 4-wire service. Two of the three secondary phases and a neutral are run to the EVSE which ends up with 208 volts phase to phase. This type of distribution is also seen in high rise apartment buildings and in some cases, underground fed subdivisions.

- - - Updated - - -

But again, all the EV's are single-phase capable and the J1772 connector doesn't support 3-phase either. So adopt the Type2/Mennekes connector to fix that problem.

That is the issue, not the general availability of 3-phase power.

 

[rolosrevenge]

Volt·Amp vs. Watt, maybe?? It'd be interesting to know the power factor of that current...

Power factor - Wikipedia, the free encyclopedia

When I did charge testing at 120 V, the power factor was near .995. I'm not sure how it would be at 207 V.

 

[FlasherZ]

In residential areas, it is not uncommon to see single phase primary run-offs where one primary phase and a neutral branches off to go down, for instance, a side street or in to an area where there is no demand or requirement for 3-phase power (split winding transformers can be connected to this one phase and neutral to deliver 120/240 volts).

In rural areas, this is true for large swaths of homes and farms. In my area, we only have 2-wire primary distribution - one phase. 3 phase service to my home would require significant investment from the power company to run all 3 phases back toward the substation.

 

[mknox]

In rural areas, this is true for large swaths of homes and farms. In my area, we only have 2-wire primary distribution - one phase. 3 phase service to my home would require significant investment from the power company to run all 3 phases back toward the substation.

It may not have to go all the way back to the substation. Typically 3-phase feeders run out and along major routes with these single phase spurs coming off the main feeder. If there is a requirement for 3-phase service (some sort of industrial building going in, for example), the utility will bring in the required lines, but it may be on a contributed capital basis if just for one user.

 

[FlasherZ]

It may not have to go all the way back to the substation. Typically 3-phase feeders run out and along major routes with these single phase spurs coming off the main feeder. If there is a requirement for 3-phase service (some sort of industrial building going in, for example), the utility will bring in the required lines, but it may be on a contributed capital basis if just for one user.

Hence "toward" instead of "to".

In my case, it's a few miles.