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Need help to reuse UPS transformer

druiddroid

New Member
I have the following transformer salvaged from a broken UPS:

20210923_093950.jpg


I would like to reuse it as a lab (bench power supply). I'm not sure about which color wire which. This also have some inverter windings in it, I assume this is the same what its using to charge the battery the blue and red.

What can the 3 other pins be where should I connect the main 230V?

I don't need this for inverting but just get the max out of it, whether that is 12V 24V.
Thanks
 

Externet

Well-Known Member
Red and blue are for low voltage and high current.


Blue-black-yellow are for the high voltage. If the inverter was 230V or 115V, you will have to measure them to figure which may be a center tap. Feed about 6 to 12VAC to red/blue to measure unplugged from the board.
 

druiddroid

New Member
This was NOT a good idea I just killed another AC powersupply doing so :(
With the continuity meter I get nowhere it shows basically that both black-yellow black-blue blue-yellow are connected the ohm meter is jumping all over the place I guess you cant use it to determine this.
 

Diver300

Well-Known Member
Most Helpful Member
With the continuity meter I get nowhere it shows basically that both black-yellow black-blue blue-yellow are connected the ohm meter is jumping all over the place I guess you cant use it to determine this.
If your Ohm-meter setting on a multimeter has auto-ranging, it can be upset by the inductive loads and the range changes and never give a correct answer. On most multimeters, you can put it onto manual range setting, and the readings will be correct, even if you have to wait a moment or two for them to settle to the correct value.
 

druiddroid

New Member
This video actually helped:


Here is the info (maybe it will be useful for someone else in the future):

230V main on BLK-BLUE -> 15V AC output
230V main on BLK-YLW -> 12V AC output

Interesting construction tho, I dont know if they jjust wanted to make a 2x12V AC supply which ended up like this or why the voltages anyway I will be using the 15V with a buck converter for lower voltages I need.
 

tomizett

Active Member
These transformers have a "high" and "low" voltage mains winding, so that they can be used for both charging and discharging (inversion) the battery. The "low" mains winding is used to give battery charge voltage from nominal mains, and the "high" is used to give nominal mains from loaded battery voltage (the battery voltage being lower under load than when charging). Fine voltage control is, I believe, done by PWM.
 

gary350

Well-Known Member
LOOK at where 230 vac connects to the circuit board then follow it to the transformer. Now you know which wires on transformer are 230 vac. Connect 230 vac to the transformer then use VOM to see what voltage you get on the other wires. No guess work involved.
 

druiddroid

New Member
This topic can be closed already as it is resolved however maybe 1 more thing if you want to still keep discussing it. I wondering without the datasheet is there any way to determine how many AMPs that transformer can provide without burning it down? :)


I bought an 50A graetz bridge for it but the transformer might wont be able to do that. The numbers on it don't make much sense I already tried to google all of them so thats a railroad.
 

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