Single phase vs 3 Phase Supply - Cost Differences?

Ectophile

Thinking ahead, a three-phase supply would be ideal for charging an electric vehicle (32A for hours on end), and for running a heat pump.  A single phase could be running on its limits with that.

Risteard

Ectophile said:

Thinking ahead, a three-phase supply would be ideal for charging an electric vehicle (32A for hours on end), and for running a heat pump.  A single phase could be running on its limits with that.

Depends on the vehicle. The on-board charger, where capable of a three-phase connection, is usually limited to 11kW and not 22kW.

pmartin86

Risteard said:

Ectophile said:

Thinking ahead, a three-phase supply would be ideal for charging an electric vehicle (32A for hours on end), and for running a heat pump.  A single phase could be running on its limits with that.

Depends on the vehicle. The on-board charger, where capable of a three-phase connection, is usually limited to 11kW and not 22kW.

Interesting - How would I find out this info on the cars? What specifically would I be looking for? For example, one of the cars my Wife is quite interested in, is the Cupra Born

The new CUPRA Born 100% Electric Car | CUPRA UK (cupraofficial.co.uk)

Charging time (AC 11kW)

6h 15min

0%-100% SOC

Charging time (DC 120kW)

35 min

5%-80% SOC

Does that mean this particular car would be 11kw on a normally charger but capable of higher if available?

Risteard

pmartin86 said:

Risteard said:

Ectophile said:

Thinking ahead, a three-phase supply would be ideal for charging an electric vehicle (32A for hours on end), and for running a heat pump.  A single phase could be running on its limits with that.

Depends on the vehicle. The on-board charger, where capable of a three-phase connection, is usually limited to 11kW and not 22kW.

Interesting - How would I find out this info on the cars? What specifically would I be looking for? For example, one of the cars my Wife is quite interested in, is the Cupra Born

The new CUPRA Born 100% Electric Car | CUPRA UK (cupraofficial.co.uk)

Charging time (AC 11kW)

6h 15min

0%-100% SOC

Charging time (DC 120kW)

35 min

5%-80% SOC

Does that mean this particular car would be 11kw on a normally charger but capable of higher if available?

The on-board charger is limited to 11kW there, so when connected to a Mode 3 charge point (AC) then that is the maximum you will get. If you have a single phase supply or single phase charge point, you will never exceed approximately 7.4kW.

A Mode 4 (DC rapid charge point) actually charges the vehicle and bypasses the on-board charger in the vehicle, so can go well in excess of this.

2bFrank

There isn't much different at all between one phase and three phase in terms of cost, a kW is a Kw. However you have to balance the phases, otherwise you can be wasting a fair bit of electric that will just be going down the neutral.

Having a Three Phase will allow you to install heavier duty car chargers or heat pumps, but other than that, there isn't much of a benefit.

Section62

2bFrank said:

However you have to balance the phases, otherwise you can be wasting a fair bit of electric that will just be going down the neutral.

How does that happen?

2bFrank

Section62 said:

2bFrank said:

However you have to balance the phases, otherwise you can be wasting a fair bit of electric that will just be going down the neutral.

How does that happen?

Blimey having to think back to my exams for the science. All currents have to return to its source, so on a perfectly balanced 3 phase system you dont need a neutral, however unbalanced the neutral takes the extra load to balance it out. 

the following explains it a bit better 

All of the current entering a system must return to its source. This is known as Kirchhoff’s Current Law. In a balanced system, one phase should match the other two phases and result in no current going through the Neutral Wire. In an unbalanced system, the current must flow through the Neutral Wire, so that the balance is maintained.

The Neutral Wire should never be connected to Ground except at the power source, where the neutral is initially grounded at the generator or the transformer. Grounding the Neutral Point in a three-phase system with heavy leakage—like an inverter system—helps stabilise the phase’s voltage. A non-grounded neutral is sometimes referred to as a Floating Neutral and has very few limited applications.

Theres loads of calculators online that can calculate the excess wastage on google. 

Section62

2bFrank said:

Section62 said:

2bFrank said:

However you have to balance the phases, otherwise you can be wasting a fair bit of electric that will just be going down the neutral.

How does that happen?

Blimey having to think back to my exams for the science. All currents have to return to its source, so on a perfectly balanced 3 phase system you dont need a neutral, however unbalanced the neutral takes the extra load to balance it out. 
...

Ok, but on a domestic 3-phase supply, if you installed a consumer unit on one of the phases and ended up with an unbalanced load, how would any current from the other two phases get wasted?

Obviously there's the potential to make the network operator unhappy, and possibly for the meter to incorrectly record usage, but would a current physically flow from the two (unused) phases into the neutral?

Ectophile

Balancing the phases is a nice thing to do.

But all domestic electricity meters measure the kilowatt-hours you use.  If you have a 3 phase supply, it will still only measure what you use, and it doesn't make any difference if the phases are balanced or not.

No current is "wasted" on the other phases.  If you haven't drawn that current, then it hasn't gone through the meter, and you won't be billed for it.