Electronic – Electric fly zapper – how is this safe

capacitorhigh voltagesafety

My trusty electric fly-zapper broke, so I opened it up to have a look in case it was something simple. I have to say I was a little surprised by what I found inside: the capacitor reads 473K, meaning the capacitance is 47nF (I was able to confirm this with my multimeter).

As the charged voltage of the fly-zapper is about 2.5kV, that gives a total charge of around 120uC. I'm surprised this is so high – as electrical regulations usually say anything above 45uC can be dangerous (see, for instance, IEC 61010-1).

My question is: how is it possible this got through the regulations? Surely as it's almost 3-times the safe charge for a capacitive discharge it should be considered dangerous?

PS: this particular fly-zapper (The Executioner) doesn't have a protective 3-layer grill like some: it's pretty easy to touch the live terminals and it just feels like a static shock.

Best Answer

I don't know if this file zapper meets any standard, or how it does it. But it's extremely unlikely that the 4.7nF cap is 4.7nF at 2.5KV, particularly if 4.7nF is what you measured with your multimeter.

If you told me that the effective capacitance as 2.8nF I wouldn't be surprised. If you suggest that the working capacitance is 1n5F, I'd just say that I don't have the specifications for that capacitor.