Hi.

I got my hands on a new but faulty EVBOX charger (3 phase charger for an electric car) and would appreciate any help in finding the source of the problem.
When the charger is plugged into the mains (3phase 230VAC + N + PE) it goes into fault mode indicated by a red light.
When I measure the voltages on the main connections I get the following result:
L1-L2: 412V
L2-L3: 412V
L3-L1: 412V
L1-N: 236V
L2-N: 236V
L3-N: 239V
L1-PE: 93V
L2-PE: 156V
L3-PE: 146V
PE-N: 63V

There is clearly something wrong with the device as:
phase to PE reads between 93 and 156V (should be around 230V)
PE to N reads 63V (Should be close to 0V)

I tried to desolder the blue tyristors and the grey surgearrester on the right of the main supply thinking these could be leaking to gruond. This had no effect.

L1 is used to power the DC circuits (control and protection part of the CB).
This leads me to think that there is some problem with the inverter/rectifier part for L1.

 

As the voltages to N are correct, this looks to me like a PE fault and maybe the charger detects that and shows a fault.

 

As the voltages to N are correct, this looks to me like a PE fault and maybe the charger detects that and shows a fault.

Hi Albert.

I think you are correct in your reply that it is an earth fault.
Do you have any advice how to locat the fault location / faulty component?

 

I am not a qualified electrician and the rules and arrangements vary between countries so anything I might say would only apply to my limited experience in UK,

Where are you in the world? That may help someone who knows your locality may be able to offer help. Failing that you should consult a qualified electrician.

 

I am not a qualified electrician and the rules and arrangements vary between countries so anything I might say would only apply to my limited experience in UK,

Where are you in the world? That may help someone who knows your locality may be able to offer help. Failing that you should consult a qualified electrician.

I'm in Finland.

I've been reading up on safety capacitors as there seem to be a bunch of these. A failed Line to ground capacitor could probably cause a leak between L1 and ground but when measuring resistance over the capacitors they all seem fine (infinite ohms) or could they still be faulty? Could a faulty capacitor start leaking when higher voltage is applied?

 

But the ground should be able to absorb that small current and keep the voltage at zero (-ish) all the way up to enough current to blow the fuse or trip the breaker.

 

But the ground should be able to absorb that small current and keep the voltage at zero (-ish) all the way up to enough current to blow the fuse or trip the breaker.

We have tested the charger at two different locations with two completely different power supplies. So I would like to say for certain that there is nothing wrong with the ground the incoming cable as the results are the same at both locations.
*The only logical reason I can think of is that some component is leaking phase to ground but there is still high enough resistance so it does not blow a fuse.

So coming back to the capacitor... Can a cap between phase and PE fail causing a leak (not a full short circuit)?

 

A good capacitor on an AC supply will pass some small current, depending on its valu. This is not a leakage current.

 

With it unplugged can you measure the resistance between the PE pin on the supply plug and PE on the unit?
Should be zero or very close.

 

With it unplugged can you measure the resistance between the PE pin on the supply plug and PE on the unit?
Should be zero or very close.

Yes I can confirm that the resistance on the plug to ground on the CB is 0ohms

 

Found out that both sides of what I believe to be a capacitor are grounded. Can anyone confirm that the circled component infact is a capacitor?
Also found in the same area of the CB several points with approx. 250ohms to ground. Would this be normal?