Togle switch amps

Why are switches being rated at different amps ?

I see lots of them on ebay rated for 10 maps at 240 volts and 20 amps at

120 volts.

Looks to me they should have the same amp rating at all voltages. The do not specify any kind of load like something that would draw a larger current at startup with a higher voltage.

Reply to
Ralph Mowery
Loading thread data ...

It's because of the arc ratings on switching to off.

--
"I am a river to my people." 
Jeff-1.0 
 Click to see the full signature
Reply to
Fox's Mercantile

'tain't the turn-on that's the issue, it's the turn-off. That's why fuses rated at 250VAC are also rated at 32VDC.

A friend of a friend was severely injured a couple of weeks ago by an arc flash at a 480V breaker panel. Turning off high-energy circuits is no joke.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
 Click to see the full signature
Reply to
Phil Hobbs

** The same switch is likely rated at 20 maps for DC switching up to 24V. Above that voltage, contact to contact arcing will become very severe or continuous.
** You gotta be kidding.

Inrush surge capacity is another matter, requiring both heavier contacts plus a strong switch off force to pull contacts apart that have become slightly welded.

.... Phil

.... Phil

Reply to
Phil Allison

I have seen the results of a 480 volt 3 phase 'blow up', Fellow at work turned on a breaker that was only a 20 amp rating for a small motor. Not sure what hapened, but it melted down a whole bank of about 30 or 40 cubicals in a load control center. That bank ws fed with around 400 amps from a larger breaker in what we called a substation room. It meleted out the bus bars on that load control center.

When working I dealt with 480 V 3 phase equipment almost daily. Lots of

10 to 100 hp motors and some heaters that were fused at 250 amps.
Reply to
Ralph Mowery

It's good to wear the Nomex suit and helmet when hacking with that stuff. The FOAF was burned over more than 50% of his body. :(

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
 Click to see the full signature
Reply to
Phil Hobbs

higher voltage means more energy in the arc for a given current. It also means more ability to sustain the arc. DC is more able to sustain an arc than ac, for the same v,i.

NT

Reply to
tabbypurr

They say that those make good body bags.

--
Boris
Reply to
Boris Mohar

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.