Charging the Roadster - EU Style

[BBHighway]

The Dutch answer is "gas". We use gas to heat everything.

That sounds scary! Don't you worry about your house blowing up with all that explosive stuff flowing through!

I guess any high power appliance can be dangerous if it's not engineered properly, regardless of the energy source.

 

[dpeilow]

So a crude 3 phase -> DC rectifier looks like this.

Simple :wink: Tesla - stick one of those in the back please...

That *is* of course the best solution!

A cheaper solution could be to use a 400V->230V transformer (300 euro for a 10kVA model; I just found a supplier) and then charge from two phases. Someone with more knowledge on this will surely be able to tell how (and if) the 120-degree phase difference translates to sqrt(3) saving.

I'd say 400V/36A = 230V/63A (roughly).

Do you have a link to the supplier?

 

[EV_de]

Six-Pulse Bridge rectifier - B6

DC Voltage Waveform:

If you run this with only 1 Phase and Nutral the DC Voltage Output will have a bigger ripple (gap between the Bumps)
therefore the average Voltage is lower and of course the Power-Output

 

[raymond]

So a crude 3 phase -> DC rectifier looks like this.

But that doesn't make use of all available power, does it? It just spreads the load evenly of the three phases, but only draws a load from each single phase at it's peak voltage.

Using 400V (or better: a proper three-phase AC -> single-phase AC converter) *does* reduce the load on each phase. [I think; please correct me if I'm wrong]

Can anybody confirm that a crude 3 phase AC -> DC rectifier is a bad idea?

I got a very informal EUR 300-EUR 600 quote from Noratel for their 10kVA transformer.

If anybody can find the price for a 3-phase AC -> 1-phase AC converter I'd be interested.

 

[Alpine Driver]

raymond,
more technically experienced people will hopefully answer your questions in a more detailed way.
But look at the datasheet (wiring diagramm) of your mentioned device:

http://en.noratel.ezpublish.no/content/download/4497/392228/file/2LT-23.pdf

this is a "simple" voltage up/down or even only galvanic isolating device; it has nothing to do with more phases or with load balancing.

 

[dpeilow]

But that doesn't make use of all available power, does it? It just spreads the load evenly of the three phases, but only draws a load from each single phase at it's peak voltage.

I think that is sort of the point. As long as each phase is in the positive part of its cycle, it will be contributing to the DC output, hence contributing power. This is where your 1.73 is coming from...

raymond,
more technically experienced people will hopefully answer your questions in a more detailed way.
But look at the datasheet (wiring diagramm) of your mentioned device:

http://en.noratel.ezpublish.no/content/download/4497/392228/file/2LT-23.pdf

this is a "simple" voltage up/down or even only galvanic isolating device; it has nothing to do with more phases or with load balancing.

Which is why you can't do this with a "normal" transformer.

Seems there are dozens of single phase -> three phase products, but not much demand for going the other way...

 

[dpeilow]

In the absence of a suitable solution, a UPS with minimal batteries is the next best option. "Double Conversion Online" signifies that it is always going through the rectifier/inverter rather than passing through power straight from the input.

This one would supply 32A safely: Emerson GXT2 10kVA TOWER UPS - Misco.co.uk

Datasheet

As you can see, not very portable and not cheap, but in the ballpark of the HPC. It's cheaper than AlpineDriver's contact thought too. This may help out some people for their home charging situations. We'll keep working on the portable one :wink:

 

[dpeilow]

OK, there are some devices out there which do what we want (search for frequency converters, power factor correctors, that kind of thing), but the bottom line is that none are smaller or cheaper than that UPS when you are talking about 10+ kVA. I've reached that point where I am going around in circles finding the same products.

So it would appear that if you want to charge from three-phase at home and not annoy your supplier, get an online/double conversion/VFI UPS. At least you can charge for a bit during a power failure :smile:

 

[AndrewBissell]

Now, if only the Roadster allowed a trailer to be towed: we could mount such a UPS and a *lot* of battery. Trailable range extender! (not useable while driving of course, but get you out of a jam if you misjudge the range to next charger - and when you encounter say 16A 3-phase (common all over continetal Europe) you can simultaneously recharge the Roadster at 40A and use the remaining capacity to charge the battery.)

we can dream.

 

[raymond]

this is a "simple" voltage up/down or even only galvanic isolating device; it has nothing to do with more phases or with load balancing.

Yes and no. It IS a simple voltage transformer, however since the three phases are 120 degrees out of phase, you can load two of the three phases equally giving you 400V instead of 230V. This in turn enables you to draw a current which is 1.73x less than what you would need to draw from a single phase 230V.

It's a partial solution which only loads two phases, but it is highly efficient, affordable, low-tech, unlikely to break, etc. It's 1.73x as good as loading a single phase, and 1.73x as bad as using all three phases.

Are their any prices out their for a proper converter (with or without UPS capabilities)? Any ideas about efficiency?

 

[dpeilow]

Thing is, the Roadster doesn't do 400V. So your idea could get expensive.

Furthermore, the transformer in your link is *only* single phase.


I looked at 'converter' prices, but there was no advantage over a UPS. Must be economies of scale.

Efficiency of a double conversion device is high 90s.

 

[dpeilow]

OK, I found another supplier of converters:

http://www.effekta.co.uk/Downloads/EF20 SFC Pamphlet.pdf

Power for power, these are slightly larger than the ATS one that Andrew found was obsolete. But, they go up to 32kVA - more than enough to run the Tesla HPC.

I called the company (the number has changed to +44 1582 882332, by the way) and got the following list prices:

8 kVA - £4466
16kVA - £5888

They said that they can normally reduce those by 10%.


They also said that a Scott T transformer would do what we are looking for, for a lot less money, however the efficiency isn't as high.

 

[Alpine Driver]

dpeilow,

thanks for this find.
Now we have the confirmation, that it IS (would be) possible to charge the roadster, even in continental DACH europe, with 70A (in the 16kVA case: 69,5A).
The negative issue is the price; I have converted it and xe gave me 6.868 EUR for that value. Lets reduce it by about 10% to 6k EUR - but as for industrial electronics, you surely have spoken about prices excl. VAT - so here in austria we have 20%, which means we are at 7.200 Euros. And then there is transportation costs.... its not mentioned how "heavy" the device is, but from the dimensions and the looks ...

Another problem is heat dissipation. Datasheet says under load, for every 1000W load -> 100W of heat are generated. So when charging with 16kVA, you have constant 1600W of heat generated from the device (seems to comply with the 90% efficiency).
So just imagine, for the charging time of 4 hours, a heater blower with 1600W is running. This will result in problems. For charging, less ambient temperatures are extremely important. See tread "energy consumption while sitting", etc.; at TM owners section. With that heat source, you wont efficiently charge, and in summer, you simply have a problem in your garage.
So, depending on the size of your garage, add 4k EUR to EUR 8k for a stationary air condition including installation.
But then - with the air condition running - see overall energy efficiency (AC, Inverter, roadster itself).

Hmm. I like the Schieflast more and more :wink:

 

[dpeilow]

You can see that there is no size advantage and certainly no price advantage of taking the smaller converter over a readily available UPS, in this case. But the option is there.

As for heat dissipation, how much heat does the Roadster itself emit while charging? If it takes >70kWh to fill the 53kWh battery, this suggests 1/4 of the 70A from the HPC is going into heat, in which case 1kW from the phase converter is the least of your worries. Best get a heat pump and warm your house :smile:.


I found an interesting thread here. An Indian supplier is talking about doing this with a transformer


EDIT: So I've been thinking about this one and it is puzzling me. I think it is incorrect. The instantaneous voltages in the secondary coils add up to zero. Check by adding up the vectors for the coils in series and you get zero. I'll admit to it being a good few years since I last did this, but can anyone verify this guy's advice?

 

[Alpine Driver]

I could add some photos of my power outlet on my flickr album:
Flickr: teslatuning.com's Photostream

 

[dpeilow]

So what they've installed there is a 5 pole 3 Phase + Neutral + Earth IEC 60309 socket (Y connection) which is fully submersible and rated at 63A for 6 hours.

What is the device at the back on the heater?

 

[Alpine Driver]

This is a Schell Easycount 3 electric meter:

Manufacturer:
Schell Count -

Never trust a VDS :wink:

 

[dpeilow]

EDIT: So I've been thinking about this one and it is puzzling me. I think it is incorrect. The instantaneous voltages in the secondary coils add up to zero. Check by adding up the vectors for the coils in series and you get zero. I'll admit to it being a good few years since I last did this, but can anyone verify this guy's advice?

Seems my inkling was correct (At least my arithmetic was ok after having not done any AC circuit calcs for 15 years - and that was at school).

I asked a supplier to look into this circuit and just got the following response:

Actually David it is impossible to achieve a balanced loading on a three phase system when supplying a single phase load with a transformer

The phase shift between the three phases means the circuit you have proposed will result in an output of 0V

There are two methods of obtaining a balanced load

1. A three phase to single phase inverter
The three phase is converted to DC then a single phase sine wave AC is created by switching electronics
The three phase supply only sees the DC as a load and is thus balance on the phases

2. A motor generator set
A 3 phase motor is powered by the supply this mechanically drives a single generator
The supply only sees the motor as a load and is thus balanced

There are several methods of converting 3 phase to single phase with a transformer but you can not get a balanced loading on the three phase system with just one single phase output. It could be possible if the load can be distributed between say two single phase ring mains

So there you have it. I'd already discounted the motor-generator method as being inelegant, but maybe it is worth a look again. The last paragraph is essentially talking about the Scott T transformer - it needs two separate loads to be efficient.

So it looks like it the rectifier-inverter (or UPS) is the best method, at least until Tesla lets the cars take three-phase directly and obviates the need for the inverter.


By the way, small, high-power three-phase rectifiers are available.

Bridge Rectifier, 800V 150A 3-Phase, Sanrex DF150BA80 at The Electrostore.com - Electronic Surplus Parts & Equipment

Powerex Grids


But, this is only half the story.

 

[dpeilow]

I found a great presentation on the Mennekes EV connector standard for Europe here.


For those charging at home with 32A, check page 27.

 

[Alpine Driver]

great presentation!
I did not know of the electromechanical interlock - so no "mobile connector" - no cable can be stolen!