3 phase EV Charger on 2 phases.

[sheppertonspark]

Hi all, I have a site where the network cable was damaged do DNO has provided 3no. 100 Amp Fuses. 1 Fuse on L1, 2 Fuses on L2. L3 is damaged in the road and not in service. I have looked at onboard charger diagrams of several vehicles. As far as I can make out the "3-phase" capable vehicles have 3no. single phase rectifiers creating the DC voltage to charge the battery. With this in mind do you think that the L1,L2,L2 combination would work ?. I can only see issues with the Neutral current due to un-balanced load.
Your thoughts would be greatly appreciated.

 

[Simon47]

I think the answer is likely to be "nobody knows".
As lot will depend on how the system as a whole monitors things - quite possibly it might upset something. Plus, as you say, the design will have made assumptions about neutral currents which will no longer be valid (just trying to visualise it in my head, I'm thinking the neutral could be around 1.5 times the individual line currents while the design will have assumed the worst case will be no higher than any line current).
Also, there may be assumptions about ripple current in the system. Genuine 3ph will result in a 6peak output, while your ------- 2 phase supply will only give a 4peak output. That means higher ripple currents in capacitors and the potential for damage.

Also, has the DNO said anything about the neutral conductor capacity if you load it to 2x line capacity which is impossible to do with genuine 3ph ?

Isn't the answer to complain about not having a 3phase supply when it's being paid for, and get the DNO to fix the fault rather than fudge the issue with the potential for breaking things.

 

[sheppertonspark]

I think the answer is likely to be "nobody knows".
As lot will depend on how the system as a whole monitors things - quite possibly it might upset something. Plus, as you say, the design will have made assumptions about neutral currents which will no longer be valid (just trying to visualise it in my head, I'm thinking the neutral could be around 1.5 times the individual line currents while the design will have assumed the worst case will be no higher than any line current).
Also, there may be assumptions about ripple current in the system. Genuine 3ph will result in a 6peak output, while your ------- 2 phase supply will only give a 4peak output. That means higher ripple currents in capacitors and the potential for damage.

Also, has the DNO said anything about the neutral conductor capacity if you load it to 2x line capacity which is impossible to do with genuine 3ph ?

Isn't the answer to complain about not having a 3phase supply when it's being paid for, and get the DNO to fix the fault rather than fudge the issue with the potential for breaking things.

Thank you for your reply Simon, good point about the DNO and 3 phase supply. I will ask my Customer to follow this up.
Although not correct and will still imbalance the neutral, the incoming cable is 3 core CNE. They have tapped off one of the phases twice on the main feeder cable outside of the property. Old paper-lead, with 1 core "down".
I have contacted Porsche to ask them if they believe this scenario will damage their onboard charging equipment. Basically asked if its 3no. single phase and neutral inverters or true 3-phase in star connection. I reckon it would be the former since how would a standard single phase 7.2 KW charger work ? Not likely to have 3-phase inverter and a separate single phase one, too expensive. I have seen circuit diagrams that show both examples "Online" however they are only study papers.

 

[brianmoooore]

I'll be interested in any definitive answers to this thread, since I have a 230-0-230V, so called split phase supply, and have wondered if I could utilise this to get 14.4kW charging. I suppose the EV itself makes the decision, and my charge points get used for all makes.

 

[sheppertonspark]

I'll be interested in any definitive answers to this thread, since I have a 230-0-230V, so called split phase supply, and have wondered if I could utilise this to get 14.4kW charging. I suppose the EV itself makes the decision, and my charge points get used for all makes.

The answer will come from Vehicle Manufacturer's. If they are brave enough to commit !

 

[Simon47]

I'll be interested in any definitive answers to this thread, since I have a 230-0-230V, so called split phase supply, and have wondered if I could utilise this to get 14.4kW charging. I suppose the EV itself makes the decision, and my charge points get used for all makes.

Ah, now that's a different question, and I'd say the answer would probably be no. Bear in mind that your split supply is probably nearer 480V than 460V RMS between lines, vs 415V for standard 3ph. While all equipment should be designed to cope with short term surges to that level, some might not like being fed it all the time - and that includes your charge point/wall socket as well.
OK, it's only an extra 15%, but that's still 15% more than most equipment will have been designed for.

The answer will come from Vehicle Manufacturer's. If they are brave enough to commit !

And then there's the problem where :
The manufacturer of the current car says "OK", so you install the charger accordingly. Then you change the car and forget to ask, or sell the house and the new owner doesn't know they need to ask, and the new car can't accept it ? There's risk of expensive damage there.

So, lets assume one situation where the charge system does have 3 independent inputs, each connected line-neutral. In this case, both will see the 240 L-N voltage so all OK there. But whereas on 3ph, at the higher power, the DC ripple will be reduced due to the 120˚ spacing of the phases, on split phase it'll be roughly double that on single phase as the full wave rectified DC would be in phase between the two inputs. That may take some components past their limits.

But at least you shouldn't burn out the neutral.

I'd say there are too many unknowns, and too many "things might change in the future" possibilities, to make this a safe thing to do.

EDIT: Oh yes just thought of this: The charge point will probably turn off due to the voltages being out of tolerance - so it assumes a broken PEN and disconnects everything. Same with the L1-L2-L2 "not 3 ph" originally mentioned.

 

[brianmoooore]

Ah, now that's a different question, and I'd say the answer would probably be no. Bear in mind that your split supply is probably nearer 480V than 460V RMS between lines, vs 415V for standard 3ph. While all equipment should be designed to cope with short term surges to that level, some might not like being fed it all the time - and that includes your charge point/wall socket as well.
OK, it's only an extra 15%, but that's still 15% more than most equipment will have been designed for.

And then there's the problem where :
The manufacturer of the current car says "OK", so you install the charger accordingly. Then you change the car and forget to ask, or sell the house and the new owner doesn't know they need to ask, and the new car can't accept it ? There's risk of expensive damage there.

All cars are designed to charge from single phase, even if they can also utilise three phase, so they must have a charger that's OK with 230 (240) V. So are they fitted with three identical single phase chargers, or a completely separate three phase charger?