Running Led security lights from a inverter

[Steve and Denise]

I have some Led security lights running from the inverter in my van, these are 30w with Pir fitted when I have them plugged directly into the mains/ house they function correctly, but when they are powered from my inverter they stil come on and off but always have a slight glow from the leds.
I am not sure why this happens the inverter is a Waeco 1800w pure sine wave.

 

[Two on Tour]

Is this when you switch off the lights and the inverter is still running or switching off both the inverter and lights Steve?

 

[Steve and Denise]

Hi Paul
i have used the van inverter to power all of our outside lights ie drive lights 22 @1.8w each and two auto pir flood lights the flood lights work as they should but when they switch off (ie at rest) they have a faint glow for some reason inverter power still on.
I I run them on mains the light switches off completely with no glow until activated again.

Steve

 

[Tombola]

its all over my head BUT, seems better quality LEDs

A pure sine wave inverter creates the sine wave using a high-frequency PWM signal. If you connect a good-quality oscilloscope to the inverter, you would detect these high frequency harmonics on the output. Moreover, the LEDs in question even light up with a few microamperes, as shown in the youtube videos. Moreover, the N and L channels are both floating when running off the inverter. Thus the high frequency harmonics still reach the LEDs over the N wires. Additionally, as it is a real physical system, there is always a small amount parasitic "innate" capacitance of both N & L wire segments after the switch (this is not the same effect as attaching a discrete capacitor component in parallel with the LED, nor the same as attaching said capacitor in serial irrespective if 1 or both terminals would be connected. Rather, this is due to the innate capacitance any conductive object, even a single piece of wire, has. For more info, see the videos).

These 4 facts COMBINED (not any one by itself), explain why the LEDs light up on the inverter, but not on utilities/generator, since the wiring in the house creates sufficient capacitance at high-frequencies, but not mains frequency. "Sufficient" here only applies to the LEDs, not to other appliances, since these are so sensitive, and only applies since the N line is NOT grounded (not because it is Grounded as Peter assumed).

So the solution becomes to Tie one of the Inverter Output lines to GND, while keeping that GND connected to the house GND or mains N/GND. Either case would suffice to keep the N line to which the LED is attached to, stably at 0V, ie it absorbs the high frequency harmonics, such that even the LEDs wouldn't be sensitive to it, and wouldn't glow. Connecting the Inverter's GND to the House GND doesn't suffice to prevent harmonics from appearing on the N line. The N line also needs to be connected to the GND. Although this defeats the safety purposes of having GND, it isn't an issue if done only when connected to the inverter, rather than utilities. The GND line of the Inverter is probably only present to detect faults, it doesn't bind N to 0V.

Also, this phenomenon only appears with the very simple/cheap (not necessarily a bad thing, I love cheap) LEDs, since the ones with more complicated circuitry (and often include galvanic isolation through an embedded transformer) insulate the LED from the harmonics or absorb them instead.

 

[pappajohn]

Floating earth on the inverter....in other words a virtual earth.
On mains there's a direct connection to earth.
A mate had the same problem in his house....no earth present on that circuit.
Try earthing the inverter case to a metal earth with a jump lead.

^{_{Subscribers  do not see these advertisements}}

 

[Nirvanauk]

Oscilloscope, now that's a word I haven't heard for many a year. When working in Bermuda in the 70's I used to balance mine between my legs while riding the company moped to the next job. Ah, sweet memories.

 

[LithiumConvert]

Post deleted by me as it was clearly wrong. sorry.

 

[Steve and Denise]

Well thanks for the explanation although I do understand most of the basics and have used the earth from the vehicle to ground at the changeover switch box, I think the inverter is a floating earth.
it all works as it should I was just curious as to the reason.
I know I have to much time on my hands

 

[autorouter]

If it's a problem with high frequency harmonics like Tombola says, then you could try looping the wires through some ferrite beads, which is a standard way to cut down unwanted high frequency transmission. It's very common in many electronics gizmos, my laptop power supply has a ferrite bead on its output wire for this reason.