This time, the issue is with cheap capacitors used in some compact fluorescent light (CFL) bulbs. The following photo is taken from the electronic ballast of a CFL that failed during the first year of its use:

Bad Capacitor in CFL electronic ballast

As you can see that the bulging top clearly shows signs of leakage. The capacitor used in this particular CFL is rated 22uf/200V with a maximum operating temperature of 105 degree (Celsius). Under normal conditions, this capacitor should be fine. But with a lot of interior light fixtures that are recessed into the ceiling, the heat generated during normal operation can easily approach this limit and causes the CFL to fail prematurely. Many failed CFLs I had over the past few years exhibited similar capacitor problems. And apparently, the general quality issue of CFLs has been concerning.

It seems to me though that the easiest way to fix this issue is for manufacturers to use electrolytic capacitors with higher operating temperature rating and lower ESR. Since the majority of CFL electronic ballasts utilize only one electrolytic capacitor, the increase in cost should be minimum.

As we know, the power factor of a purely resistive AC circuit is 1.0. Typical household electronics contain inductive or capacitive elements and thus have a non-zero phase angle between the current and voltage. This non-zero phase angle results in a power factor less than 1.0.

To improve power transmission efficiency, we would like to have the collective loads to appear as close to purely resistive as possible. If the power factor of the loads is significantly less than 1.0 then significant amount of energy is wasted during power transmission due to power line resistance.

So as a curiosity, I decided to measure the power factors of a few compact fluorescent lamps. Since one of the primary reasons people chose to use CFL’s is to save electricity, I had expected that the power factor of these CFL’s to be relatively high. But to my surprise, typical CFL’s found common in Home Depot and Walmart have rather low power efficiencies. For the CFLs I measured (ranging from 10W to 40W) they all have a power factor of just above 60%.

Clearly, more energy could be saved if the power factor of these CFLs are higher. But manufactures see no need of adding cost to their final products by adding power factor correction circuitry. After all, typical consumers only care about how much electricity they can save. Whether the power factor is 0.6 or 0.8 it doesn’t matter as the savings are pretty much the same regardless of the power factor. As for the environment it is a totally different story: the higher the power factor, the less energy it is wasted during power transmission and thus the better it is for the environment.