[SML] PLASA public Review documents

[e-mail frank.wood95]

It all depends on the type of brealer, and on the nature of the load.
Motor start rated breakers are designed to handle start-up surges, and
work for incandescent lamp loads too, where the cold current at switch
on is typically ten times the running current. Some DC power supplies
also have start surges.

Magnetic breakers are the most susceptible to surge currents, although
ELCBs (GFCIs), while magnetic, probably are not, since they are only
looking for out-of-balance currents in the live and neutral lines.

As for harmonics, these can only come from funny loads, such as big
rectifier sets such as you find in big welding shops. Thermal breakers
make a true RMS current measurement, and can be slugged with a small
heat sink of some sort.

On 5 October 2014 00:55, bruce--- via Stagecraft
<stagecraft at theatrical.net> wrote:
>>Just for curiosity, I read some of these drafts.
>
>>I shall never, never ever, understand the approach to overcurrent
>>production that means that a 100A breaker may be loaded to 80A, and no
>>more. If I buy a 100A breaker, I expect it to carry a load of 100A for
>>ever and a day. How long it takes to trip with an overcurrent depends
>>on the magnitude of that overcurrent, its duration, and on the detail
>>design of the breaker. The manufacturer's data usually include this
>>information.
>
>>If I want an 80A breaker, I will buy one, and expect not to get a 64A
> breaker!
>
> ++++++++++++++++
>
> Startup current and temporary surges, not to mention harmonics on the line.
> Measurement of current flow is a game of averages when dealing with AC
> current, and so de-rating at least partially attempts to account for this
> and prevent so-called 'nuisance trips'.
>
>   Your quibble is with the labeling?  You'd prefer the manufacturer to
> de-rate and then label as such?  What happens when some intrepid soul
> discovers the 'secret' capacity left and loads to that capacity and then
> has a nuisance trip every day and so jams a clothespin against the handle?
> Or even just goes on the net spouting about the terrible design of company
> X?
>
> My admittedly testy .02
>
> :Bruce Cooper
>
>
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-- 
Frank Wood