[slp_prlzys]

Hi,
can I use a transformer from a UPS? (Uninterruptible Power Supply)
I acquired an APC 520ES UPS, and looking
inside it I found a huge transformer, and I was wondering
if I could use it as a power supply, if so, what current
capability can I expect from it? I'm guessing it's
a kind of step-up transformer, but does it work the other
way?

thanx.

[PEU]

I used one from an UPS, but I rewired it (actually a shop did it )so I can have multiple secondaries:




Pablo

[slp_prlzys]

I got brave enough and tried it,
with the transformer that I have
I'm getting 16V AC not using the center tap
so, basically I have two 8V which would drop
when I use bridge rectifier. I might try rewinding,
but need to do a lot more reading from the other thread.
Actually I just wanted to build a bench PSU so I guess 12VDC
should be enough for now, I'm just curious how much current this
thing could handle.

[smarbaga]

with bench supplies you very seldom need much more that 1 or 2 amps.
maybe you should consider using a variac with its o/p into a bridge/ cap filter setup for larger current needs.
you can feed the variac into transformers as well.
this way one can bring the ac/dc up slowly in experimental circuits, before the fireworks.
been there , done that , lol

[slp_prlzys]

I forgot about this.
I'm reviving the thread for yet another question.

BTW I built a simple PSU using LM317 and a walwart trnsformer,
found a circuit online.

My new quest.
I decided to use the txformer from UPS to power
my steppers( currently have one), but I'm
not quite sure how much current it could supply.
How do I determine the current.
this txformer used to have two 6Ah batteries connected
to it( though not directly).

Also can bridge rectifiers be paralleled, ( I'm thinking I could,
since diodes could be paralleled right?) I just happen to have
a bunch I took from old AT PSUs, and I'm cheap I'm trying
(to save)let me rephrase, not to spend as much
If it could be paralleled, I still need to know the current from the txformer.
The bridges I have can handle 4A, (it says so in the datasheet I got).

tia.

BTW why(how come)does some transformer hum? 'cause this one hum
noticeably.

[vulcom1]

If you have 16vac without the centre tap you should get 16vdc using a bridge rectifier. Connect your 2 ac lines from the transformer to the ac lines on the bridge and there should be a + - on the bridge for your dc out. The rectifiers I have seen are all marked.
Hope this helps.
John

[slp_prlzys]

vulcom1:
thanks, but I'm more concern 'bout current capability
of the transformer, and the possibility of using
two bridge rectifier parallel.( and the humming )
but I guess the hum is no big deal, I hear the
the transformer on the lamp post accross the street when
I walk by, nobody seems to care.

[Al_The_Man]

You can get an idea of the VA from the physical size of the core. Transformer hum is often caused by either loose laminations or also increases when under load.
Al.

[H500]

Diodes cannot be hooked in parallel. They will not split the load equally.

[slp_prlzys]

Diodes cannot be hooked in parallel. They will not split the load equally.

Dang, I was hoping I could make use of those bridges if
the txformer is more than 4A


Al_The_Man: I just thought that I could derive the value
from available info i.e. 6Ah batteries used, and the unit's
output is [email protected] when it's still a UPS as you
can see in the pic it's been stripped off.

.thanks.

[Al_The_Man]

There's no definitive rule, but I would guess the size to be around 200~250va tops.
Al.

[slp_prlzys]

I'll try to test it like this, say, I use the bridge that is rated 4A,
would the bridge blow up if the txformer can supply more than 4A,
or do I have to put load first then I'll know if it will blowup?
That way I could assume that I have more than 4A txformer,
then figure up another test

[Al_The_Man]

The current is dependant on the load, no load - no current.
If you exceed the va rating of the transformer it will overheat and the voltage may start to collapse.
Al.

[slp_prlzys]

Thanks, I should have known that, still a lot to learn.