We live in a world that is different than just a few years ago. Not only are LEDs everywhere, but VFD controlled appliances and heat pumps and PWM regulated ovens etc. are increasingly common. These loads are rapidly switching causing line voltage to sag and rise over and over. This combination of factors has added a new source of light flicker that apparently hasn't been widely reported on. The old one/off loads would just cause a minor dimming that was normal and hardly noticed. But this rapid switching is very visible now. I first noticed two years ago. I bought a new "inverter direct drive" washer. And the cheap LED in my dining room went crazy when the washer was running. Flicker rate of between 3 and probably 20 Hz. I tried a better quality LED lamp and it definitely helped, but it didn't solve it completely.
I did some experiments with different lamps to see what would work, and of my locally available choices I found that expensive Philips LED bulbs didn't flicker and also incandescent and CFL were steady.
But now, I'm running into trying to explain this to customers. Obviously the best answer for the time being is "don't buy cheap bulbs", but that just isn't going to sit well with them. Already I've seen the skeptical glint in their eyes as I'm explaining the theory. Too bad, I know, but we need to push this out there more. The internet is at present very sparse on this info. Searching for this exact phenomenon leads to the classic explanations of light flicker: bad connections, large loads momentarily kicking on, etc.
One job I have has the inverter-driven mini-split heat pumps making 300 cheap LEDs in a ballroom flickering. They were unwilling to change the bulbs because they aren't satisfied with the look of the lamps necessary to be effective. So I installed a double conversion online UPS for the lighting circuits. This works very well... EXCEPT every now and then, when the heat pumps begin to ramp up, the UPS goes to battery only mode for a few minutes with subsequent annoying alarm. At this job I have the freedom to casually poke around and so I took the heat pump cover off and temporarily added 50000 uF of capacitance to the DC bus ahead of the VFD. There is 2000 uF already built in. This experiment worked like a charm. Even without the UPS, the flicker is ALMOST unnoticeable. This tells me that appliance manufacturers could solve the problem, but probably won't.
So please spread the word and let me know what other angles we can attack. Sorry for the long winded post.
I did some experiments with different lamps to see what would work, and of my locally available choices I found that expensive Philips LED bulbs didn't flicker and also incandescent and CFL were steady.
But now, I'm running into trying to explain this to customers. Obviously the best answer for the time being is "don't buy cheap bulbs", but that just isn't going to sit well with them. Already I've seen the skeptical glint in their eyes as I'm explaining the theory. Too bad, I know, but we need to push this out there more. The internet is at present very sparse on this info. Searching for this exact phenomenon leads to the classic explanations of light flicker: bad connections, large loads momentarily kicking on, etc.
One job I have has the inverter-driven mini-split heat pumps making 300 cheap LEDs in a ballroom flickering. They were unwilling to change the bulbs because they aren't satisfied with the look of the lamps necessary to be effective. So I installed a double conversion online UPS for the lighting circuits. This works very well... EXCEPT every now and then, when the heat pumps begin to ramp up, the UPS goes to battery only mode for a few minutes with subsequent annoying alarm. At this job I have the freedom to casually poke around and so I took the heat pump cover off and temporarily added 50000 uF of capacitance to the DC bus ahead of the VFD. There is 2000 uF already built in. This experiment worked like a charm. Even without the UPS, the flicker is ALMOST unnoticeable. This tells me that appliance manufacturers could solve the problem, but probably won't.
So please spread the word and let me know what other angles we can attack. Sorry for the long winded post.