I know a little bit of knowledge is a dangerous thing, but this issue is seriously frying my brain.

I have a 5kVA Axpert Inverter, with what I think is a fault. Although it was working, I noticed that some of my LED light strings were on, yet dimmed, despite the switch being off. Called my sparky, he came and started tracing the fault, and found that there was voltage (220V) between the Earth and Neutral connectors on the AC Output side.

I sent the Inverter back to the Suppliers for repair, and they tell me there's nothing wrong with it - they can't find any faults. It has just arrived back, and before installing it, we were running some tests on it.

Without any power sources connected, we ran a straight continuity test using a standard multimeter, and there is continuity between Earth and Neutral on the AC Output side.

Surely this is not right?

43 minutes ago, Peter_DM said:

there was voltage (220V) between the Earth and Neutral connectors on the AC Output side.

That's almost certainly a filter of some kind. Did you measure this with everything disconnected? Well obviously not, because you had the LED strip plugged in...

Let me tell you an amusing story. Well, it was amusing to me. My wife was upset that I did not appear to care. It was also 3AM in the morning and I was not very awake and probably even less coherent...

It was still that time when the kids would wake up at random times during the night, and she was up sitting with a kid when she noticed the bed lamp in the other room (which is left on just for security purposes) was flickering a bit and looking a bit dim (it was obviously on the way out). So she switched it off... and the lamp remained on! She came to me, woke me up to complain about the poltergeist in the other room, and I summarily dismissed it and went back to sleep. Which did not go down well.

So what happened is simply this: This LED lamp has a small capacitor in it. The LED chips themselves have started to fail, so only a few were still working. The few that remained needed only a small bit of current to light up... and the capacitor inside the lamp was sufficient to keep the lamp lit for several seconds.

I have heard similar stories of people having a couple of LED downlights in parallel, turning off the light switch, and some of them turns off, while the others remain on (sometimes even going a bit brighter) before it all goes off.

So long story short: This might be nothing to do with the inverter. Cheap SMPSes are now used everywhere, as are EMI filters and surge suppressors. All they need to do is hold 100VDC at a few milliamp to give you the result you saw.

Edit: This is (by the way) why a good SMPS has a small burden resistor to discharge things when the power goes out. A cheap SMPS has a nice party trick: Unplug it, then push the prongs directly onto some exposed skin of your buddy next to you and watch him jump...

Edited May 14, 20197 yr by plonkster

2 minutes ago, plonkster said:

Did you measure this with everything disconnected?

Yes we did. We disconnected all loads, and selectively disconnected inputs

3 minutes ago, plonkster said:

Cheap SMPSes are now used everywhere, as is EMI filters and surge suppressors. All they need to do is hold 100VDC at a few milliamp to give you the result you saw.

I don't think that's the case in my scenario. Currently I'm in bypass mode (inverter disconnected, running on Eishkom), and the LEDs are behaving quite normally

2 minutes ago, Peter_DM said:

Yes we did. We disconnected all loads, and selectively disconnected inputs

The Axpert does have a filter on its output as far as I know. It could be that one too.

I've since been reading up a lot more of the posts in the Inverter section, and I think I now understand the continuity issue, but the Voltage issue still has me baffled.

I'm hoping for some ideas / comments before we re-connect the Inverter.

1 hour ago, Peter_DM said:

found that there was voltage (220V) between the Earth and Neutral connectors on the AC Output side.

In some models, in battery mode, there is no connection from AC-in neutral to AC-out neutral. So with those models, you have to provide your own.

1 hour ago, Peter_DM said:

Without any power sources connected, we ran a straight continuity test using a standard multimeter, and there is continuity between Earth and Neutral on the AC Output side.

Ok, so that's weird. That implies that you have the model with the extra relay contact, so that AC out  neutral and earth are connected when not in line (bypass) mode. When the inverter is unpowered, that's not line mode too, so you get the connection. So you should have connection from AC-out neutral and earth either via AC-in neutral (when in line mode), or via the relay (all other times).

What mode was it in when you measured the 220 V AC-out N to E?

Do you have a voltage between AC-in N and E? If so, something is seriously wrong with your Eskom neutral, or the wiring.

I have an LED light that glows softly at night when the switch is off. There seems to be enough capacitance in the wiring to provide a dribble of power to the lamp, and LEDs don't need much power when it's pitch dark to emit a glow.

The high neutral to earth voltage is a concern and needs to be fixed, but I don't see the connection to the LEDs staying on dimly.

 

4 hours ago, Peter_DM said:

...there was voltage (220V) between the Earth and Neutral connectors on the AC Output side...

 

4 hours ago, Peter_DM said:

Without any power sources connected, we ran a straight continuity test using a standard multimeter, and there is continuity between Earth and Neutral on the AC Output side.

 

 

Hi @PeterDM

the two states descibed above are mutally exclusive. If you have a solid continuity between E+N, then you cannot have a 220V between E+N at the same time.

I bet that you've measured the E+N continuity when the Axpert was turned off, which is a different state from when Axpert is running in the battery mode.

If you have a bit of electrical skills, do this quick-check:

• Have the Axpert running in the battery mode, powering the loads.
• Connect the standard 220V incadescent bulb (not LED) to the AC-OUT, between E+N.
• If the bulb will lit, you have an issue.
• If the bulb won't lit, then short the AC-OUT E+N and the "problem" is solved.

Trust me, my friends call me "The Expert"

Edited May 14, 20197 yr by Youda

An update regarding this issue; in case anybody else has the same (or similar) problem.

It turned out to be a stupid, simple mistake. On the Utility Input cable, the Live and Neutral were reversed at the other end of the cable. This also explains why the LED lights were glowing - the switch was disconnecting the Neutral instead of the Live connection.

Thanks all for your input / advise.

1 hour ago, Peter_DM said:

On the Utility Input cable, the Live and Neutral were reversed at the other end of the cable.

Ah! I should have twigged to that from the 220 V (not 90 V as is more commonly seen) between neutral out and earth.

It's one of those errors that someone like myself can't conceive of making. I'm not saying I would never make that mistake, though I sure hope not, just that I'd never think to check for it.

Great to hear that it's sorted.

7 hours ago, Peter_DM said:

An update regarding this issue; in case anybody else has the same (or similar) problem.

It turned out to be a stupid, simple mistake. On the Utility Input cable, the Live and Neutral were reversed at the other end of the cable. This also explains why the LED lights were glowing - the switch was disconnecting the Neutral instead of the Live connection.

Thanks all for your input / advise.

Thanks for comming back with the above update. It's good for self-education

Hi all

I have Axpert 5kva 4000kw but find ny LED glow after switching off. Also have a reading of 133v between L + G and 33v N+G o AC out. My EL also trips (not the main switch or 20a circuit breaker from AC out to loads 2 x 10a lights abd 2 x 20a plugs. Can it be my L&N AC OUT should be reversed?