the symptoms were relay arcing on the apc backups pro. it was producing the buzzing sound. while it was running off the batteries. output to load was ok in both cases, running off the mains or from the battery.
so i take the backups apart and replace all 3 untransparent relays even though only one was damaged(the one in the middle). (i did the same for my smaller backups device, so i thought it should work here too...come to think of it on my backups symptoms were slightly different; buzzing and flickering the load(for example lightbulb hooked to it flickers) was happening even when it was on mains...first symptom was it suddenly gave up.
otoh backups pro was not turning off the load or flickering it, it was just struggling...)
then i got to play with outputs: i notice the following: no arcing buzz when pc is not connected.
connect monitor, connect amp etc. it's ok, but as soon as you connect pc, it gets confused and it buzzes when running off the batteries.
(smaller backups unit(like the one i have...300va) was shutting down when mains was disconnected....it was supposed to run from batteries but it would just shut down).
then i remembered this psu has a-pfc, so i fetch p-pfc fortron and hook it up, and sure enough everything is back to normal, no buzzing when it's running off the batteries, and smaller backups unit is working as expected.
the only explanation i came up with so far:
a-pfc circuitry is somehow cycling the energy so that backups pro(650va, i think) is on the limit of what it can and can't do.
at one moment load is acceptable, at another it goes over the top and then protection shuts it down.
but this is happening at such frequency that it's destroying the relay rather fast. big arcs etc.
smaller backups was not affected because it's weaker, it cannot provide enough energy at any point, it just shuts off immedietely and stays shut.
the whole thing is probably connected to something we discussed earlier
https://www.badcaps.net/forum/showth...&highlight=apc
but it's not just that old design ups' can damage the psu, but some a-pfc designs can damage the ups units.
huh...
one backups 650 already paid this with its life. but perhaps i'll be fixing that one...it seems switchers (and offcourse relay) pay in the end.
found this
http://episteme.arstechnica.com/eve/...1#725004899831
"Power fails
UPS starts supplying square/jagged wave 'power'.
PSU chokes and shuts down.
UPS shuts down, since there is no load.
(all happening within the first few milliseconds of the event)"
that's consistant with what i've said, only in my situation ups is shuting down, but then turning on again, in rapid succesion.
could probably be explained by psu choking and shutting down/powering up in a same manner.
either way, a bad-bad a-pfc on that chieftec!
this one
https://www.badcaps.net/forum/showth...light=chieftec
bad for these old apc backups anyway.
backups pro
http://www.apc.com/resource/include/...TOKEN=80837878
(offourse, 230v model here)
the one it already destroyed
http://www.apcc.com/resource/include...se_sku=BK650MI
something else i've found
http://www.hardforum.com/showpost.ph...9&postcount=10
apparently designing ups doesn't have much to do with trying them in the field...
gee is one dumb bastard...but also a "professional"...huh...
i should buy few more fortrons with p-pfc as sine wave ups are too expensive.
so i take the backups apart and replace all 3 untransparent relays even though only one was damaged(the one in the middle). (i did the same for my smaller backups device, so i thought it should work here too...come to think of it on my backups symptoms were slightly different; buzzing and flickering the load(for example lightbulb hooked to it flickers) was happening even when it was on mains...first symptom was it suddenly gave up.
otoh backups pro was not turning off the load or flickering it, it was just struggling...)
then i got to play with outputs: i notice the following: no arcing buzz when pc is not connected.
connect monitor, connect amp etc. it's ok, but as soon as you connect pc, it gets confused and it buzzes when running off the batteries.
(smaller backups unit(like the one i have...300va) was shutting down when mains was disconnected....it was supposed to run from batteries but it would just shut down).
then i remembered this psu has a-pfc, so i fetch p-pfc fortron and hook it up, and sure enough everything is back to normal, no buzzing when it's running off the batteries, and smaller backups unit is working as expected.
the only explanation i came up with so far:
a-pfc circuitry is somehow cycling the energy so that backups pro(650va, i think) is on the limit of what it can and can't do.
at one moment load is acceptable, at another it goes over the top and then protection shuts it down.
but this is happening at such frequency that it's destroying the relay rather fast. big arcs etc.
smaller backups was not affected because it's weaker, it cannot provide enough energy at any point, it just shuts off immedietely and stays shut.
the whole thing is probably connected to something we discussed earlier
https://www.badcaps.net/forum/showth...&highlight=apc
but it's not just that old design ups' can damage the psu, but some a-pfc designs can damage the ups units.
huh...
one backups 650 already paid this with its life. but perhaps i'll be fixing that one...it seems switchers (and offcourse relay) pay in the end.
found this
http://episteme.arstechnica.com/eve/...1#725004899831
"Power fails
UPS starts supplying square/jagged wave 'power'.
PSU chokes and shuts down.
UPS shuts down, since there is no load.
(all happening within the first few milliseconds of the event)"
that's consistant with what i've said, only in my situation ups is shuting down, but then turning on again, in rapid succesion.
could probably be explained by psu choking and shutting down/powering up in a same manner.
either way, a bad-bad a-pfc on that chieftec!
this one
https://www.badcaps.net/forum/showth...light=chieftec
bad for these old apc backups anyway.
backups pro
http://www.apc.com/resource/include/...TOKEN=80837878
(offourse, 230v model here)
the one it already destroyed
http://www.apcc.com/resource/include...se_sku=BK650MI
something else i've found
http://www.hardforum.com/showpost.ph...9&postcount=10
apparently designing ups doesn't have much to do with trying them in the field...
gee is one dumb bastard...but also a "professional"...huh...
i should buy few more fortrons with p-pfc as sine wave ups are too expensive.
Comment