I forgot to mention that the transformers also have 2 seperate pairs of 115V mains connectors, marked PRI1 115V BROWN -BLACK, PRI2 115V BROWN -BLACK


I did little drawing, so would this be right way to drive a 12V computer fan with two of these trannys?

 

If each transformer has two of the 115 volt primaries, they are already 230 volt transformers.
and you don't need the 10 ohm resistor to get rid of 3 volts. A 12 volt fan will not drop dead at 12.7 volts. If you want to "fix" that non-problem, just add another diode to get rid of the extra 0.7 volts.

 

If each transformer has two of the 115 volt primaries, they are already 230 volt transformers.
and you don't need the 10 ohm resistor to get rid of 3 volts. A 12 volt fan will not drop dead at 12.7 volts. If you want to "fix" that non-problem, just add another diode to get rid of the extra 0.7 volts.

I got the fan running by connecting two of these transformers in series, but I when I tried only one with both of its primary connectors on 230V, the transformer just made weird buzz and the fan didnt spin.. I Hope i didnt break it, it was only couple of seconds though..

 

I got the fan running connecting two of these transformers in series, but I when I tried only one with both of its primary connectors on 230V, the transformer just made weird buzz and the fan didnt spin.. I Hope i didnt break it, it was only couple of seconds though..

No, I doubt you broke it, but not for lack of trying.
So why did you connect it different from the way your were told?
Random connections to electrical devices often don't end well.
As I stated, you need to connect both transformers to the same load, so that the secondary, and thus the primary currents are the same in both transformers.
Otherwise one transformer tries to supply the current but is blocked by the other primary carrying no current, which looks like a high impedance inductor (the primary magnetizing inductance).
The transformers then just sit there and do nothing but buzz, as you noted.
Any other random experiments you'd like to try?

 

No, I doubt you broke it, but not for lack of trying.
So why did you connect it different from the way your were told?
Random connections to electrical devices often don't end well.
As I stated, you need to connect both transformers to the same load, so that the secondary, and thus the primary currents are the same in both transformers.
Otherwise one transformer tries to supply the current but is blocked by the other primary carrying no current, which looks like a high impedance inductor (the primary magnetizing inductance).
The transformers then just sit there and do nothing but buzz, as you noted.
Any other random experiments you'd like to try?

I tried cuz the other dude told that they were 230V transformers... Ill now connect two in series and check the outputs with multimeter to find out if its broken.

Okay, connected them back to series and all the outputs are seeming to give what they should. I just dont under stand why there is four connectors for input current, cause when I connect only one pair from them they work fine..

 

Hello,

Could you post a picture of the transformers?
Also a picture of the label on the transformers will help.

Bertus

 

It they have two 110V windings on the transformer then you can connect the two input windings in series on one transformer with the proper polarity (brown to black) and you don't need the other transformer.
To prevent blowing anything when testing this configuration I recommend placing a 220V incandescent bulb in series with the primary when connecting it to the mains.
If the light doesn't light or glows dimly you are okay.
If the light shines brightly then the connection is wrong.

 

Hello,

Could you post a picture of the transformers?
Also a picture of the label on the transformers will help.

Bertus

The abbrevitios are in finnish, KE = YEL, HA = GREY, LI = VIO, VI = GRE, MU = BLK, RU= BROWN, VA= WHITE, PU = RED, SI = BLUE

 

I think Ill go with just one 230V primary voltage transformer, that I have, on my project .. I have tranny which has 230V input and 18VAC 120W output, im planning to drive 10, 10W power leds and their max current is marked at 1050mA, trough vellemans K8042 ( http://www.velleman.eu/products/view/?country=be&lang=en&id=353668) It has 1A max input so the current would be too much for ten leds, but I intend to drop the voltages to 10V with resistors for each (theres 5 blue power leds which want 8-10V and 5 daylight leds that want 9-11V), For just incase I ordered two K8042's for connecting five leds per, How would I connect those to the normal toroidal transformer with four output wires?

 

Hello,

It looks like you are having two black (MU and MU1) and two brown (RU and RU1) wires on the transformer.
Those are the connections for the two 115 volts entrances of the transformer.
I assume that the MU connections are one side of the winding and RU the other side.
As crutshow said, connect them in series and use a lamp for test as he said.



Bertus

 

Hello,

It looks like you are having two black (MU and MU1) and two brown (RU and RU1) wires on the transformer.
Those are the connections for the two 115 volts entrances of the transformer.
I assume that the MU connections are one side of the winding and RU the other side.
As crutshow said, connect them in series and use a lamp for test as he said.

View attachment 102046

Bertus

Wow, thanks, this actually worked... both different voltage outputs with different watts are giving what they should, Do you think by leaving open or connecting them somehow together the unused outputs, would give more wattage handling to the used ouputs?

 

The core has a certain VA rating. You cannot exceed this. When the transformer was designed, the wire size was selected to support a certain amount of current without overheating. So, the tradeeoff is operating a little warmer with a larger voltage drop when other windings are unused and the used windings are overloaded.

Nonetheless, a 5W fan will only draw 5W even when connected to a 1,000,000 Watt power source.

 

Hey, Is it somehow possible to get, with two, of these transformers or even with four, 48V provided to 48VDC>12VDC transformer, via two of vellemans
K7203 transformers? ( http://www.velleman.eu/products/view/?id=9381 )