joules

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thomasf

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Hi everyone, (New Guy here, well last couple months, anyway so go easy on me)
In a clsoed post I read about what CharlieB wrote about S and P ok what about Joules how do they fit in to this mix ??
The surge suppressors they sell are all rated in joules not watts or VA.
Why is that. and what exactly is a joule.

Tom
 
Re: joules

watts/second is the answer, its an energy measurement. For surge protection, some suppliers viewed this as almost a joke. If you have resistance, then you have joules. The more resistance, the worse the surge protective device. I am seeing units sized in KA.
 
Re: joules

NEMA requires TVSS's to have a kA/mode (thousands of amps per mode of protection)rating.
It is too easy to fool an observer with a joule rating. A joule rating is watts x second.
So some manufacturers will show a tremendously high joule rating, but it is a low wattage passed over a very long period of time.

edited for formula accuracy - rs

[ October 22, 2003, 01:53 PM: Message edited by: ron ]
 
Re: joules

In TVSS the Joule rating is meaningless unless quantified with time verse amps. Ignore the Joule rating, it is a gimmick as Ron mentioned.

"AMPS PER MODE" is one of the ratings you want to look at. Ignore "amps per phase", again another gimmick, it is an simple addition of all the "modes" connected on each phase and cannot be tested or proved.
 
Re: joules

Others have correctly identified ?Joule? as a unit of energy. However, it was incorrect to express a Joule in terms of ?Watts/second.? The correct relationship is

(1 Joule) = (1 Watt) TIMES (1 second)

Looking at it from the other direction, ?power? is the rate at which energy is being generated, transmitted, or used. This could be expressed as follows (actually, this is the definition of a ?Watt?)

(1 Watt) = (1 Joule) / (1 second)

Taking it one step further, consider your home electricity bill. It is based on energy usage in units of ?kilowatt-hours.?
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">(*) (1 kilowatt-hour) = (1000 watts) times (1 hour)
    (*) (1 kilowatt-hour) = (1000 watts) times (3600 seconds)
    (*) (1 kilowatt-hour) = 3,600,000 Joules</font>
<font size="2" face="Verdana, Helvetica, sans-serif">
And just in case you have not yet had enough, consider the following definitions:
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">(*) A ?volt? is the amount of energy (in Joules) that it takes to move one unit of charge (in Coulombs) from one point to another.
    (*) An ?Amp? is one unit of charge (in coulombs) passing a given point in one second.
    (*) Multiplying (1 volt) times (1 amp) is the same as (1 Joule/1 Coulomb) times (1 Coulomb/1 second).
    (*) Therefore (1 volt) times (1 amp) gives (1 Joule/1 second)
    (*) This is the basis of the formula P = V x I</font>
<font size="2" face="Verdana, Helvetica, sans-serif">
 
Re: joules

Thanks Charlie. Thats the best explaination I have seen.
I feel one of the reasons we don't understand power is we use different units and don't understand how they relate: BTU's, HP, Watts, Tons of AC....
 
Re: joules

Charlie
Thanks for the clarification.
So if 1 watt = 1 joule/ 1 second then the amount of power or energy for one cycle would be, assuming AC, would be Volts * amps / 60.
So a 100 watt bulb for one cycle / 60 would be 1.66 joules per cycle.
The statement that the advertising on these surge strips is 'bogus', makes me wonder maybe they are saying for a surge/transient, which by themselves are not long in duration that this is the energy absorbed before the 'surge-strip' opens to protect the circuit.
I dont know thats why I am asking
Thanks again
Tom
 
Re: joules

Originally posted by itreader:What does NEC have to say about this?
Click to expand...
Say about what? What does the NEC say about Joules? That word does not appear in the NEC. What does the NEC say about surge suppressors? 285.2 defines Transient Voltage Surge Suppressors, and talks briefly about their connections. But the NEC has nothing to say about the way they are rated. If that doesn?t help, then I guess that I don?t understand the question.
 
Re: joules

DereckBC: NEMA has a specifiers guide to TVSS units. Have you seen it? It is a form you fill in with the various ratings of the TVSS.
 
Re: joules

This sounds alot like the major false selling spree that has seem to have taken a grip on our manufactures in our country (United States) as any more I cant think of any thing that is not being misrepresented! from HP of car engines to the power output of stereo systems. Even vacuum cleaners and air compressors, Down the common hair dryer in our bathrooms 1800 watts yea right!
When are we going to put a stop to this false advertising? It was never allowed before and when we saw this kind of claims we called it flea market junk. but it is now rampant through out the market. and needs to be stopped as the unknowing public is getting ripped off!
 
Re: joules

As far as the surge-surpressors go, the Joule rating is not a rip-off( or Slick Marketing and Packageing) but rather rating of the energy absorbtion level of the device.
If a unit had a rated level of 1200 J. Then
W = Pt = EIt:
If say a 5000 volt spike came down the line. The product It = W/E = 1200 J/5000 V = 240mA x S
The rated energy level shows that a current of 100 amps could be sustained for t = 240mA x S/100 amps = 2.4 mili-seconds.
When looking at from this perspective the word joule has quite a different meaning and is certainly Truth in advertising.
Most of these units have a 180 volt MOV acros the line which is the heart of the device, and alot of these units come with a lifetime guarantee not bad for about 20 bucks.

WOC
 
Re: joules

The measurmeent of joules is not standardized enough.
My TVSS can supress the wattage equal to a 5W light bulb for 60 minutes and my TVSS will essentially Blow if anything significant of a spike should hit it. :D
 
Re: joules

WOC, I respect your opinion, but the Joule rating is only the combined value of all the MOV?s installed in the TVSS unit. It does not take into the account of the unit?s total impedance, and quantified with a time and amperage value. A 5 KV @ 2.4 milli seconds is not a transient voltage surge event, it is an over voltage condition, which would fry any TVSS device on the market. Test waveforms are on the order of 8/20us

Instead what you should look for in a TVSS is a published UL-1449 Second Edition SVR rating of 330 volts and ignore the ANSI clamping voltage. You should also look for the ?amps per mode? and not a joule rating or ?amps per phase?.

The joules, amps per phase, and ANSI clamping voltages are theoretical values and cannot be tested on an assembled unit because it does not take into consideration the lead and fuse impedances with respect to a time value.

It is OK for a manufacture to list the joule and amps per phase rating, but if they are not publishing the UL-1449 Second Edition SVR, ANSI 62.41 cat C3 and/or B3 NEMA LS1 ?amps per mode? rating, and NEC 285 KAIC compliance, they are hiding something they do not want you to know?
 
Re: joules

Dereckbc,

The pulse rating for surge surpressors: "8/20uS", I've never found a really clear explanation of what that meant. Is that just a way of saying eight pulses in 20 microseconds?

Thanks.

-John
 
Re: joules

Originally posted by big john:
Dereckbc,

The pulse rating for surge surpressors: "8/20uS", I've never found a really clear explanation of what that meant. Is that just a way of saying eight pulses in 20 microseconds?

Thanks.

-John
Click to expand...
8000 amps rise in 20 micro seconds up to what ever the publised "amps per mode"
 
Re: joules

Dereckbc:
For some reason I couldnt D/L the info you pasted.
I however did check as many Tvss strips as I could find, and the majority listed UL 1499 and some listed 1497 as the Eval. standard.
I believe we are on the same track here since Energy is what this field is all about. We install a 200 amp service in lieu of saying a 48kva system.
To say that these strips do NOT absorb energy is incorrect, the joule rating is used on a short term basis.
Spikes, transients , surges are short duration, and yes you are correct it will problably be toast when all is said and done.
The more expensive models had a lifetime guarantee, as I said above, but as you have already noted they smoke which is the case.
Spikes and surges are notorious for going through transformers be it lightning or a line abnormality. case in point, Isolation transformers do not protect SCR drives as once believed, drive paks will smoke real quick and the isolation transformer will just carry the spike right through to the scr pak and totally wipe it out. When this first happened, the first to see was the huge MOVs totally blown apart, and of course the first thought was. " Great they did their job, unfortunately, upon closer inspection the whole board was toast.
The 'amps per mode' is understandable, but with out a voltage pushing it, it means little. and hence the power associated with it, however, short the duration.
WOC
 
Re: joules

My experience has been that it is the smoke and mirrors technique applied by many surge suppressor manufacturers. If you look and the ANSI/IEEE waveform standards C62.41 and C62.45, they test in terms of amps times microseconds. To try to convert those proven transient waveforms to a joule rating is crazy. I have found that if you use a quality plug strip with a UL 1449 Listed sticker on the plug strip (not just the box it comes in- which is the case more often than not) and there is a panel unit ahead of the plug strip- you should not have any damage to your electronics.
 
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