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What is the true definition of the clamping voltage on a surge protector?

3K views 1 reply 2 participants last post by  Bird dog 
#1 ·
Unfortunately, my high school actually had a really horrible physics teacher and we literally learned nothing about circuits. Doubly unfortunate is that I regularly work with electricians for my job so I'm always trying to learn this stuff from the web which isn't always the best way.

Anyway, this might sound like a stupid question but what is the exact definition of the clamping voltage on a surge protector? What is the exact definition of the let-through voltage?

I ask this question because there seem to be different definitions of these two simple terms online. My two additional questions still deal with figuring out what clamping voltage is.

On the below website, the two terms appear to be defined to be almost the same. The let-through voltage rating equals the total voltage allowed to reach your equipment, taking into account: surge suppression, noise reduction, and line conditioning.

people.richland.edu/dkirby/172surgesuppressors.htm

On many websites, "experts" agree with the definitions of these 2 words. Look at: zerosurge.com/glossary/

However, in the article below, it's defined slightly differently. The clamping voltage is the voltage in which the MOV clamps and so is the voltage that is allowed to reach your plugged-in device. But, let-through voltage is the difference between the clamping voltage and the peak of the nominal AC voltage of the power line (which is about 170V). (Look at the first sentence in the second paragraph.)

arstechnica.com/gadgets/2016/06/from-the-wirecutter-the-best-surge-protector-for-your-home-electronics/2/

Is the writer of this article totally wrong about what let-through voltage is?

However, Tripp Lite seems to define clamping voltage (RMS) totally differently. In Tripp Lite's technical specifications (link below) for most of their surge protectors, the clamping voltage (RMS) is stated to be 150V. It appears that they are incorrectly defining the clamping voltage to be the difference between the voltage when the MOV clamps and the peak of the nominal AC voltage (170V). In other words, the MOV clamps at 320V (170V + 150V).

tripplite.com/protect-it-12-outlet-surge-protector-8-ft-cord-2880-joules-tel-modem-coaxial-ethernet-protection~TLP1208SAT

Strangely, in the white paper below by Tripp Lite, it seems to define clamping voltage and let-through voltage correctly this time, sort of stating that the two terms are the same thing. It's not really clear. (Look at the bottom paragraph on page 6.)

assets.tripplite.com/white-paper/how-to-choose-the-right-surge-protector-white-paper-en.pdf

Now, the website below suggests something weird about clamping voltage. The website below states that the lowest possible voltage protection rating (same thing as clamping voltage, right?) is 400V for AC power applications? (Look at the last sentence in the second-to-last paragraph.) Why can't it be 330V? I've seen many surge protectors with UL 1449 ratings of 330V.

lowellmfg.com/wp-content/uploads/LowellSSlet.pdf

Are the online "experts" using the same definitions of let-through voltage and clamping voltage but I'm having a brain fart somewhere?
 
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