[futaro]

Hi,
I am wondaring How can ZOE guarantee its insulation safety when AC charging?

Usually, a EV has a inslated On Board Charger (OBC), it is insulated bacause the OBC has an transformer.
I think the transformer taking some part of insulation safety.
On the other hand Zoe, it has a unique AC charging system using rectifier, motor coil, and inverter.
but hey, there's no transformer there in ZOE, can it granatee its insulation safety or anything related to AC charging safety?

 

[donald]

It looks for grounding leaks.

In fact, all Renaults are rather renowned for OVER-looking for earthing leaks and being hypersensitive, and the 'DANGER ELECTRICAL FAULT' and 'BATTERY CHARGE IMPOSSIBLE' are dash board messages far too common for stranded Renault EV users.

Also, the AC power to DC conversion probably happens via a coupling capacitor which is a DC block so in theory would prevent DC earth current to mains. I can't say if that is present or even helps but there is also capacitive isolation in most SMPS type power converters these days.

 

[95199]

Hi,
I am wondaring How can ZOE guarantee its insulation safety when AC charging?

Usually, a EV has a inslated On Board Charger (OBC), it is insulated bacause the OBC has an transformer.
I think the transformer taking some part of insulation safety.
On the other hand Zoe, it has a unique AC charging system using rectifier, motor coil, and inverter.
but hey, there's no transformer there in ZOE, can it granatee its insulation safety or anything related to AC charging safety?

The motor coil is only used as part of the SMPS on the Q motors where 43kW charging is available. Because these motors are also water cooled (the R motors are air cooled) there was a perceived issue with mains leakage which I why I believe the Zoe is particularly critical about having a low earth resistance connection which causes some owners to have problems in getting the car to charge even when there is no fault with the car. I think the Zoe is probably the safest car to have connected to the mains.

 

[Jeremy Harris]

The Zoe is pretty clever, and has this covered. Because there is indeed a greater potential risk in using the motor windings as inductors for the switched mode supply (because they cannot be double insulated) the Zoe tests to make sure that the car has a good earth connection via the charger. It does an earth loop impedance test during the initial power-on stage, before the on board charger starts to operate, and will not power up if it detects that there is an earth fault. AFAIK, the Zoe is the only EV that does this, and it's a very good built in safety feature. All other EVs just assume that the charge point earthing is OK, and also assume that a fault that may make the body of the car live is extremely low, primarily because of the insulation level on all the AC side components from the plug to the OBC.

 

[Andy-Zoé-User]

I thought both Q & R models had Chameleon that used motor coil windings as the transformer part no?

Its a shame there is no adjustment though (it seems) as to how sensitive the Ohms of the ground when the Zoe will refuse to start charging.

i mean I dont want to see it as being dangerous or causing electric shock to anyone , but on the other hand if you were to turn up to a charge point and the earth was absolutely fine ... but zoe was fussy about it because it was out of its threshold and if you had a laptop handy with diagnostics software on it (LOL ) you could just adjust the earth impedance of the Zoe slightly for it to charge instead of just driving off to find another charge post

 

[Jeremy Harris]

I thought both Q & R models had Chameleon that used motor coil windings as the transformer part no?

That's the issue. If you look at the motor windings, they are like any motor, just single insulated. Nothing wrong with that at all, but it does mean that the Zoe is a little tiny bit more reliant on having a good enough earth loop impedance that the body cannot momentarily rise to too high a voltage if there was an insulation breakdown. It does the earth loop impedance test to check that, which makes a lot of sense. It wouldn't be a bad idea if all EVs did this, TBH, as it's easy enough to do and people aren't very diligent when it comes to testing that their RCDs still operate correctly. Doing this test before it starts every charge makes the Zoe charger about the safest OBC I know of.