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Unread 24-09-2016, 14:08
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
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Re: LED bulb question

The two bulbs might operate at different power factors (PF).

Power factor is defined as the ratio of power (Watts) consumed to apparent power (Volt-Amperes) drawn. Resistors and old-fashioned incandescent light bulbs operate at unity power factor, because all the current they draw follows the applied voltage instantaneously; no lag, no distortion. Inductive loads such as transformers and AC motors operate at less than unity power factor because their current draw lags the applied voltage. Electronic loads, such as the AC to DC converter circuits inside LED light bulbs, operate at less than unity power factor because their current draw is distorted relative to the line voltage. But, not all AC to DC converter circuits are created equal; some distort more than others, so some operate at lower power factor.

The first bulb in your example operates at PF = 8.5 / (120 x 0.15) = 0.47

The second bulb operates at PF = 10 / (120 x 0.12) = 0.69

It would be worthwhile to test these two bulbs using an inexpensive meter such at the Kil-A-Watt, to see how well actual performance tracks their markings.
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I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
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