Electronics > Beginners
Brymen BM235 10A fuse silently destroyed by a switched off UPS leakage current..
IanB:
It was a fast blow fuse. Maybe the fuse blew before the RCD had time to act?
hgg:
Fast blow fuse, but with how much energy?
From its data sheet : "Intended to carry 100% of rated current indefinitely." which is 11A.
The RCD tripped with less than 30mA @ 230V in a couple of milliseconds.
How much energy did the fuse receive in order to blow before the RCD?
Its obviously less than the energy received by the RCD.
Somebody to do the math? ???
malagas_on_fire:
Look at page 2 of the datasheet , the graph and watch the time vs possible Amps on the fuse and compare to the RCD one :
http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/product-datasheets-a/Bus_Ele_DS_1047_DMM-B.pdf
Enough energy to prevent further damaged to meter or user
IanB:
--- Quote from: hgg on March 06, 2019, 08:23:49 pm ---The RCD tripped with less than 30mA @ 230V in a couple of milliseconds.
--- End quote ---
The RCD will also trip with 30 A in a couple of milliseconds. It will trip with 300 A in a couple of milliseconds. How do you know how much current actually was present when the RCD tripped and when the fuse blew? (You said a 40 W bulb tripped the RCD, so that was 40 W / 230 V = 170 mA. Already much more than 30 mA.)
Bear in mind that based on the previous comments in this thread where you had the mains polarity reversed, it appears you had the full power of the mains live conductor available to supply current. If you connect that to earth/ground you could expect to see hundreds of amps flowing in cases where the earth conductor is bonded to neutral at the supply.
Since you blew a 10 A fuse, you can deduce that much more than 10 A flowed through the fuse at the time it opened.
malagas_on_fire:
The BM235 has low-z mode but be carefull AutoV (LoZ). Check page 7 of its manual .
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