Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Supercharger Buck Boost Transformer Specifications

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
I finally got close enough to one of the buck/boost transformers that I see at various supercharger locations to get specs off of it.

As suspected, they added these to reduce the input voltage by about 5% using an autotransformer. My understanding is that the second generation charging circuitry for the S/X (which is what the v2 superchargers were based on) is sensitive to voltages above like 282 ish volts. They kick offline if the utility voltage is too high.

Then the utility provides 480/277 three phase (and be inverters are connected phase to neutral and so nominal voltage is 277v), but the utility may fluctuate up and down by like 5%, so that created an issue sometimes. I think this is also why they removed from the Wall Connector instructions the allowance to hook it up at 277v.

So I am tempted to install Wall Connectors at commercial locations using small single phase 277v autotransformers with similar specs to these rather than stepping all the way down to 240v or 208v.

These are the Washington Square Urban Superchargers off 217 in Portland Oregon just for reference. Also, I am thinking that the urban superchargers are different from the long haul superchargers in that the twelve 12kW rectifiers in them don’t have switching in them to let them latch on to either DC bus (for the two cars). They are hard connected to a single bus (less things to fail). Then they also probably don’t need as large of conductors to the vehicle drop cords as the long haul superchargers.

Anyway, just putting this info out there in case anyone else is interested! Making sure it is on the google search cache for future folks!

4714C387-978B-4489-83F6-E566ED813C62.jpeg
0ADC1A60-EB15-4D20-AEAF-744C9B59F5C2.jpeg
E7CB8673-F083-4FDB-BBAE-74061D91FA99.jpeg
D2AC56EA-949E-4D5A-A578-374AED6847AD.jpeg
 
  • Informative
Reactions: darth_vad3r

MrMassTransit

Supporting Member
Mar 7, 2019
299
506
Washington, DC
Then the utility provides 480/277 three phase (and be inverters are connected phase to neutral and so nominal voltage is 277v), but the utility may fluctuate up and down by like 5%, so that created an issue sometimes.

With the caveat that I don't have an expert-level understanding of electrical distribution infrastructure, I have a question about this. I realize you're talking about using one of these in a HPWC installation application, but does your statement that "inverters are connected phase to neutral and so nominal voltage is 277v" refer to an HPWC or a Supercharger setup? I had always assumed that a Supercharger was connected across all three phases and was using the full 480v as a result. Is that not correct?
 
  • Like
Reactions: eprosenx

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
With the caveat that I don't have an expert-level understanding of electrical distribution infrastructure, I have a question about this. I realize you're talking about using one of these in a HPWC installation application, but does your statement that "inverters are connected phase to neutral and so nominal voltage is 277v" refer to an HPWC or a Supercharger setup? I had always assumed that a Supercharger was connected across all three phases and was using the full 480v as a result. Is that not correct?

I was talking about superchargers, but the same holdstrue if you hook up a Wall Connector to 277v. It is connected phase to neutral.

So from what I can figure out about the superchargers, they have twelve modules in them and each one is ~12kW or a little bit more (48 amps times a little under 277v due to the buck transformers). That gives you a max of about 144kW if they are all functioning and you are not paired with another car. I presume that four are on phase A, four on phase B and four on phase C within each cabinet.

So in this configuration all the power of the three phase system is utilized, but each device only deals with 277v vs. 480v.

Does that make sense?

P.S. I wish Tesla could just certify me to be a contractor on their supercharging stations. Each time I was at a station I would work on fixing whatever is broken. :) I get the feeling that rectifier modules are broken all the danged time but that it is hidden from the users since you never really know why you are getting lower charge rates (you assume the paired car is sucking down the juice).
 
  • Like
Reactions: MrMassTransit

Petrlol

Member
Oct 16, 2018
403
543
Ohio
So I am tempted to install Wall Connectors at commercial locations using small single phase 277v autotransformers with similar specs to these rather than stepping all the way down to 240v or 208v.

So you're thinking you could do 277v - 5% to get 263 - 277v (if the source is coming in 277+5% variance) at 48amp for 12.6 - 13.2kW from a destination HPWC?
 
  • Love
Reactions: eprosenx

gfunkdave

Member
Aug 10, 2016
133
184
Portland, ME
So from what I can figure out about the superchargers, they have twelve modules in them and each one is ~12kW or a little bit more (48 amps times a little under 277v due to the buck transformers). That gives you a max of about 144kW if they are all functioning and you are not paired with another car. I presume that four are on phase A, four on phase B and four on phase C within each cabinet.

So in this configuration all the power of the three phase system is utilized, but each device only deals with 277v vs. 480v.

Does that make sense?
.

From what I have seen all three phases of 277/480 go into each supercharger, with 53kW per phase available (i.e., a 160 kVA transformer feeding each station).
 
  • Informative
Reactions: eprosenx

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
So you're thinking you could do 277v - 5% to get 263 - 277v (if the source is coming in 277+5% variance) at 48amp for 12.6 - 13.2kW from a destination HPWC?

Correct. And in a previous email thread with Tesla about this they even suggested a “buck” transformer like this to do precisely what you describe.

Now the Model 3 has some other limit and so won’t ramp to a full 48 amps on 277v, but it will get close.

The big win here is that in commercial installations you don’t need a huge step down transformer, the buck autotransformer is much smaller physically. It should also be cheaper and more efficient.

I do wish Tesla would have found a way to make all the cars 277v compatible (including the utility variance tolerance). That would have been awesome.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,124
Canada
Trivia: some utilities like Con Edison and Pepco provides 265/460V instead which reduces the charge rate.

Hmm. Could they not use the transformers posted by @eprosenx above to boost 5% instead of buck if the chargers want higher voltage input?

Not sure if they are hitting power supply limitations ... if not, that should work and give them the voltage they want (if they indeed want higher) without losing the current they desire as well.

380-480 V / 192 A is the input label. That’s 160 kW for 3-phase, right?

So from what I can figure out about the superchargers, they have twelve modules in them and each one is ~12kW or a little bit more (48 amps times a little under 277v due to the buck transformers). That gives you a max of about 144kW if they are all functioning and you are not paired with another car. I presume that four are on phase A, four on phase B and four on phase C within each cabinet.

So in this configuration all the power of the three phase system is utilized, but each device only deals with 277v vs. 480v.

@eprosenx how does your “144 kW” jive with the newer upper limit of 150 kW?
Wait, actually, how’d you get 144? 12 x 48 A x 277 V = 159.5 kW, even minus 5% is still 151.5 kW.
 

miimura

Well-Known Member
Aug 21, 2013
6,358
6,063
Los Altos, CA
Hmm. Could they not use the transformers posted by @eprosenx above to boost 5% instead of buck if the chargers want higher voltage input?

Not sure if they are hitting power supply limitations ... if not, that should work and give them the voltage they want (if they indeed want higher) without losing the current they desire as well.

380-480 V / 192 A is the input label. That’s 160 kW for 3-phase, right?



@eprosenx how does your “144 kW” jive with the newer upper limit of 150 kW?
Wait, actually, how’d you get 144? 12 x 48 A x 277 V = 159.5 kW, even minus 5% is still 151.5 kW.
Buck-boost transformers can be wired either way. The one pictured above is a 5% shift, so it can either raise or lower the voltage by 5%.

What you calculated is 159.5 kVA. After rectifying to DC with 90% efficiency, you get about 144 kW of DC power.
 

MrMassTransit

Supporting Member
Mar 7, 2019
299
506
Washington, DC
So from what I can figure out about the superchargers, they have twelve modules in them and each one is ~12kW or a little bit more (48 amps times a little under 277v due to the buck transformers). That gives you a max of about 144kW if they are all functioning and you are not paired with another car. I presume that four are on phase A, four on phase B and four on phase C within each cabinet.

So in this configuration all the power of the three phase system is utilized, but each device only deals with 277v vs. 480v.

Does that make sense?

It does! What I forgot about was that within each cabinet there were 12 modules. Now it makes perfect sense.
 

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
@eprosenx how does your “144 kW” jive with the newer upper limit of 150 kW?
Wait, actually, how’d you get 144? 12 x 48 A x 277 V = 159.5 kW, even minus 5% is still 151.5 kW.[/QUOTE]

I was just using 12kW as rough math. It is probably a little over that each. I have never seen a supercharger actually do a full 150kW (maybe top out at 147kW?) so it was just rough. Also, we have seen that the M3 charger backs down the amperage away from 48a if it gets a full 277v, so it has some other limitation (though the M3 is a different version of the charge circuitry I think than the S and X since the M3 does not have the tolerance issue being discussed here).

I work in fiber optics a lot and we do a lot of 12 strand buffer tubes and when you have 12 buffer tubes you get a 144 count 4RU panel, so my brain just gravitated there. ;-) I probably should have said 12.5kW.

It does! What I forgot about was that within each cabinet there were 12 modules. Now it makes perfect sense.

I actually don't know it is 12 modules... I just have made a guess since we see things like 36kW charge rates when charging and the current model S and X top out at 48 amps which is about 12.5kW each. It could actually be just six modules at 25kW each.

I am making the wild guess that in non-urban superchargers there are two DC busses. One for each car, and they have some way that each module can flip flop between the two busses (so as to not join the two cars together on a common bus which seems fraught with peril).

Take what I say with a grain of salt!

P.S. Though 60a circuit breakers are very common and widely available. ;-)
 
  • Like
Reactions: darth_vad3r

miimura

Well-Known Member
Aug 21, 2013
6,358
6,063
Los Altos, CA
It actually doesn't matter how many modules are inside the Supercharger cabinet. The rating label shown above indicates that the AC input is 192A per phase. So, 192A x 277V x 3 phase = 159,552 VA.
 
  • Like
Reactions: eprosenx

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,124
Canada
Buck-boost transformers can be wired either way. The one pictured above is a 5% shift, so it can either raise or lower the voltage by 5%.

What you calculated is 159.5 kVA. After rectifying to DC with 90% efficiency, you get about 144 kW of DC power.

So how does V2 get to 150 kW displayed DC input power in the car?
 

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
It actually doesn't matter how many modules are inside the Supercharger cabinet. The rating label shown above indicates that the AC input is 192A per phase. So, 192A x 277V x 3 phase = 159,552 VA.

Yeah, I am just interested in knowing so I can understand how the modules are switched between the cars (in what increments) and when they fail, what is the mechanism of failure? 12kW at a time, etc...

That is a good note about overall capacity! So 160VA minus whatever AC to DC losses (assuming the rectifiers are perfectly power factor 1).
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,124
Canada
IIRC I've read about this 12 x individual chargers on the forums multiple times, and also had assumed the Urban SC's were the same but just with 6 modules.
 

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
So how does V2 get to 150 kW displayed DC input power in the car?

I suspect the power supplies are actually more than 90% efficient. And also, I don’t think I have ever seen my car actually make it to 150kW fully. It may often be limited by available utility voltage.

And also, it may depend on the voltage delivered by the utility. Some superchargers also I don’t think have the buck transformers (not sure if those are older units with different modules, or just in area the utility tends to deliver lower voltages).
 
  • Like
Reactions: darth_vad3r

eprosenx

Active Member
May 30, 2018
2,073
2,515
Beaverton, OR
IIRC I've read about this 12 x individual chargers on the forums multiple times, and also had assumed the Urban SC's were the same but just with 6 modules.

The urban cabinets look identical to me to the non-urban ones. Two units off each cabinet. So I think it is still 12 modules but just without the ability to ship that power to either car.
 
  • Like
Reactions: darth_vad3r

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top