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This follows on from another question I'd been asking. Having been 'gifted' dozens of mains LED lamps, I've been blithely assuming that they don't offer much in the way of inductive load.

But, of course, they aren't just a mass of LEDs: there's a rectifier, and perhaps an inverter (though a glance at the wiring of the LEDs in my lamps suggests that there's two parallel chains of 65 LEDs, which would be about right to drop 230 V).

I've searched for information, but there's nothing that I've found. Does anyone know a) if there is appreciable inductance in such lamps, and b) how one could set up a test rig to measure it? thanks

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LEDs are a nonlinear load and probably these lamps will not have a power factor correction converter. This means that the current will not be sinusoidal therefore you will have some reactive power flowing. There may be a PFC choke before the rectifier bridge.

If you want to measure the power factor and harmonic content just take a scope with voltage and current probes and measure line voltage and line current.

PS. This it how you distinguish China Export mark from European CE: enter image description here

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  • \$\begingroup\$ The Conformité Européenne vs. China Export thing is a myth: "However, the European Commission says that this is a misconception. ... in its view, the incorrect application of the CE marking on products was unrelated to incorrect depictions of the symbol, although both practices took place". Notably, there are cheap crap items that have the correct "C E" mark but would never pass inspection, and there are conforming products with the incorrectly styled "CE" mark, proving the "this is how you distinguish" advice useless. \$\endgroup\$ – marcelm Mar 18 '18 at 2:09
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I measured a few LED table lamp bulbs. The PF was 0.86. I also measured some CFLs, and the power factor was 0.90.

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The only way to really know would be to get the datasheet of the lamp or to measure it.

However, it sounds like these lamps are wired in a way that would probably not have much inductive component to their load. The large chain of LEDs in series probably means there is a full wave bridge, the LEDs, and a load resistor in there. If so, the power factor won't be great, but there should be little inductive component.

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  • \$\begingroup\$ :-) Alas, the "datasheet" is a crudely-photocopied single page, with mistranslated English instructions; they didn't really get as far as listing the inductance (though there is a cartoon of a smiling person not being electrocuted as they "correct instaliat of bulb or gasket"). (Hmm, how much confidence do I have in that CE mark on the back...?) \$\endgroup\$ – Peter Reid Mar 7 '13 at 17:22
  • \$\begingroup\$ Is it a proper CE mark or the fake? \$\endgroup\$ – Brian Drummond Mar 7 '13 at 17:29

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