On 8/7/24 10:28, Viesturs Lācis wrote:
Viesturs
trešd., 2024. g. 7. aug., plkst. 15:35 — lietotājs gene heskett
(<ghesk...@shentel.net>) rakstīja:
T=RC will give an answer for (IIRC) a 67% charge. Where T is time in
seconds, R is ohms and C is farads. 5T will give essentially a full
charge time. Its the low R from the powerline that is clearing your
fuse/breaker. :o)
Thank you Gene for detailed explanation, I appreciate it!
Ok, let it be a permanently connected resistor with a relay that
bypasses resistor when capacitor is charged.
I think that this should do the trick:
https://www.tme.eu/lv/en/details/ahp100w-47rj/power-resistors/sr-passives/
Now what about the relay? That page has SSR relays for 400V DC but
they are above 100 EUR. Is it ok to use "normal" relay as the
switching is expected without the load? I am slightly puzzled that
some relays/contactors are rated for 600V AC or 28V DC.
For discharge I think this should do (1KOhm would be 0.34A at 340V and
that is 115W):
https://www.tme.eu/lv/en/details/hs200-1kf/power-resistors/arcol/hs200-1k-f/
The same question about relay applies here as well.
Viesturs
The SSR has the advantage of a zero current turn off, no arc to quench.
In 20 years of using a 60 amp crydom lookalike by the chinese maker
hayac, about $10 a copy, rated for 600 volts, I have had one probably
lightning caused failure. And no failures since I brought my service
grounding up to NEC specs. i'm actually doing essentially the same
thing twice since the go704 has grown a 4th A axis meaning more and
bigger switching psu's. All the switchers now get a 1 second charge time
while the spindle motor gets 3 seconds. Same basic circuit now ties up 4
gpio pins in .hal. Its a 1hp rated motor, but my supply can make it
twist like a 3+. Been doing it for a decade, oem brushes in it yet.
Viesturs
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Cheers, Gene Heskett, CET.
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