Almost all my down lights in my house flicker when off if there is no power from Eskom running on the inverter or just on the generator. Why is this happening?

Another thing I have noticed is my fans in the house change speed when there is load shedding, It is audible and I can immediately hear they are running a bit slower when there is no Eskom feed is this also normal? 

Hi @JacoG

The lower speed on the fan is due to the drop in voltage.  I am supplied by Eskom.  The grid voltage ranges from 240v up to 248v at times.  My inverter was set at 220v.

When the grid goes down (load shedding), the voltage drops to 220v.  The power output (watts) given the same amps is about 10% less than when the grid is present.  The result is that motors slow down.  Geysers take longer to heat etc..

I have since set my inverter on 230v.

I also have a set of downlighters that flicker, but I think that has more to do with the dimmer switch.

 

 

Thanks Jay, so setting the inverter to 230v did not solve the flickering lights?

Our down lights in the house where all those 12V DC Downlights with each 2 or 3 lights sharing a transformer. Lights used to flicker occasionally and the transformer buzzing was driving me mad, changed them to 230V GU10 Downlights and that solved my problems. Now our dimmers don't work but that is a project for another day.

@Basil Katakuzinos  Just about all LED bulbs are overdriven.  This is done on purpose by the manufacturer, to reduce the life-expectancy of the bulbs to a few months or maybe 2 years.  LEDs, if properly cooled and kept under their maximum power rating, will last for years.  Youtuber Big Clive has made many videos discussing this and showing how to modify the lamps.  Here is a link to one of his videos: 

However, you do not always need to open LEDs to modify them.  Connecting a capacitor in series with an LED bulb will have the same effect.  This works on most, but not all lamps.  It should work on all 3W bulbs and all bulbs that only use a rectifier and dropping capacitor.  More powerful lights that use a SMPS might or might not work.

So if you are used to a dimmer, you could at least implement a 2-stage brightness switch.  Even so-called non-dimmable lights can be turned down using this method to any brightness you want.  You can make these lights so low, that they will radiate less light than a candle.

I have replaced the single light switch bezel with a dual switch.  The first switch is used to turn the light on and off and the second is used to select full/half brightness.  One could go beyond this and even use 3 or more switches and have multiple selectable brightness settings, but that is getting a bit silly.

The above method will also work if your light fitting uses 2, 3 or more LEDs in parallel.

You need to use a high voltage bipolar capacitor rated for 250VAC or 630VDC, or higher.  A 100nF capacitor will dim a light substantially.  You might want to use capacitor values from about 47nF, 100nF, 150nF, 220nf and 470nF.  Or get a bunch of 100nF and connect 2 or 3 in parallel.  The simplest way to implement this, is to simply connect both light switches in SERIES and then wire the capacitor across one of the switches.

I got tired of these LED flood-lights not lasting and always having to climb up with a ladder and replacing these.  I don't need the full brightness, I am happy with even a 10% power output.  So I replaced the LED-PCB in the flood light with that of an ordinary 5W LED bulb and then modified the small constant-current SMPS to only push about 1W into the LED cluster.  The consumption is so low that I removed the PIR movement detector and run the light 24/7.  I now expect that light to last many, many years.

Perhaps the flicker is caused because inverter voltage is steady at 230V, where as Eskom varies between 228.3V-243.5V, avg is 235.0V
Below chart is from average per day from 1 Dec 2022 to 4 Apr 2023 (load shedding excluded [V below 210 & Hz below 45])
Definite rise from ~1 Nov 2022.

Edited April 4, 20233 yr by system32

What is the THD of the inverter?

Possibly an earth neutral bonding issue.  I have seen LED lights "glow" even with the light switch OFF when on generator or inverter without earth neutral bonding.

1 hour ago, system32 said:

Perhaps the flicker is caused because inverter voltage is steady at 230V, where as Eskom varies between 228.3V-243.5V, avg is 235.0V
Below chart is from average per day from 1 Dec 2022 to 4 Apr 2023 (load shedding excluded [V below 210 & Hz below 45])
Definite rise from ~1 Nov 2022.

Interesting that you find a rising voltage. This should be area specific as in our area in Tshwane the voltage is rock steady over the same period. The min to max varies about 8V between normal day time and peak. Below is an example between LS events. 

33 minutes ago, TimCam said:

Possibly an earth neutral bonding issue.  I have seen LED lights "glow" even with the light switch OFF when on generator or inverter without earth neutral bonding.

I have a good grid N to E bond on the grid and a very slight glow is present and more so after switching the lights off even when on grid supply. My LEDs showing the glow are 1W LEDs but not visible in my 3W downlights. 

Maybe high levels of RF affecting  LED's driver circuitry? Plenty 2G and 5G RF even from local house routers. 🤔

Not enough power to drive 3W LED's but enough for the 1W LED's.

Edited April 4, 20233 yr by TimCam

19 hours ago, TimCam said:

Maybe high levels of RF affecting  LED's driver circuitry? Plenty 2G and 5G RF even from local house routers. 🤔

Not enough power to drive 3W LED's but enough for the 1W LED's.

The LEDs that I used have no normal driver. 4 of them in series on a 12V PSU for my entrance. In 2005 I used a 1W LED per room driven from a 12V battery with day/nite switch and manual override. Never thought of LS then but the system is plain and works. 

Yes without driver they can flicker when on but due to a large lead acid battery the voltage is very stable. Even these will glow directly after switch off. Luckily it does not bother me. 

Here is an explanation of what can cause correctly functioning LEDs to flicker.  (Faulty LEDs can also flicker during normal on conditions).

230VAC LED lights fall into two general groups.  Those that use a so-called transformer-less power supply and those that use a proper SMPS (switched-mode power supply).

The transformer-less designs use a non-polarised capacitor in series that acts as a voltage dropping element.  The capacitor is followed by a bridge rectifier, a smoothing capacitor and maybe a resistor and/or zener diode (A zener is a voltage clamp).  These circuits are cheap and are used for low wattage LEDs (typically anything up to 3W).  These LEDs should NOT flicker.  Any leakage current that might arise from capacitive cross-coupling between long cable runs or other conditions, will turn these LEDs on at reduced brightness.  Sometimes so dim that you can hardly see it.

Good quality LEDs and the higher powered LEDs (typically 5W and more) use a small SMPS.  Here a PWM regulator chip is used to drive the LEDs at a constant current.  The 230VAC is first rectified in a bridge rectifier, then smoothed by an electrolytic capacitor and then chopped in a step-down PWM regulator.  The regulator IC will require a minimum operating voltage to wake up and become active.  This voltage might be as low as 40V or higher than 90V.  There are many different PWM regulators on the market.  Each one will have it's own characteristics.

So here is what can happen.  The leakage current will find it's way through the rectifier and slowly charge the smoothing capacitor.  The voltage over this cap will gradually rise.  At some point the voltage will have reached the threshold where the PWM regulator chip will wake up.  The chip will now attempt to turn on the LED at it's designed brightness/current.  The smoothing capacitor will now be discharged near instantaneously.  The voltage will drop below threshold and the PWM regulator chip will shut down.  The leakage current will again start charging the capacitor and the cycle will repeat.

To prevent this, one could connect a resistor across the LED, but this will waste some power when the LED is on.  Alternatively, a capacitor can be wired across the LED.  This will also bleed away the voltage.  The advantage is that the cap will not consume (real) power when the LED is turned on.

I have found certain PWM chips that will not cause flicker and the bulb will sometimes behave in a similar way as a transformer-less LED bulb.  It all depends on the PWM regulator's internal design and component values of the circuit.  I would be surprised to find a Osram or Philips LED flickering.  It's the Chinese manufactures that want to save every last cent and take shortcuts...

I have this issue when the batteries on the inverters finally fail and the generator kicks in. Strangely it doesn't seem to affect down lights on dimmers.

40 minutes ago, Tallboy said:

I have this issue when the batteries on the inverters finally fail and the generator kicks in. Strangely it doesn't seem to affect down lights on dimmers.

Non dimmable LEDs are very sensitive from the controller side. As the voltage drops they tend to flicker. This is for a LED that is still in good order. 

The cost of dimmable controllers are higher so most sold are not dimmable. Having said that I found they cheaper one are quit tolerant of a good % of lower voltage than the spec. Around 10.5V some of mine will start to flicker - this for the 12V AC type. 

LEDs are constant current devices although we use them on voltage circuits. This is the function of the controller. 

Edited April 23, 20233 yr by Scorp007