I have a 12 0 12 transformer which works on 220 V 50 hz system.
I have to use it for 24 v output and 12 v output.
For 24v output, i connectwd it with 220 v 50 hz and secondary is not centre tapped.
For 12 v output, Can I connect it with
1) 120v 50 hz input , secondary not centre tapped. Or
2) 120 v 60 hz, secondary not centre tapped,
3) 220v 50 hz, secondary centre tapped.

What precautions I need to do before doing this?

 

What are the 12 and 24V loads. Are you using diodes? You have two 12V outputs. You can use only one.

1) 120v 50 hz input , secondary not centre tapped. Or
2) 120 v 60 hz, secondary not centre tapped,

NO

 

What are the 12 and 24V loads.
View attachment 335430

12 v and 24 v loads are ic whose supply input is mentioned as 12 v and 24 v.

From figure, is it not okay to connect with point 2 & 3 to get 24 v output at 220v,

Or 12 v output at 120v(or110v) ?

 

You can get both voltages from the 220V input and center tapped secondary. One method is to put the 24V to a bridge rectifier, with the negative diode side to "ground". That then gives the center tap as a 12V DC tap.
ie: (example at bottom is for 600/300V, but works for 24V/12V). Hope it shows ok...

https://el34world.com/Forum/index.p...ion=dlattach;topic=25003.0;attach=78693;image

 

You can get both voltages from the 220V input and center tapped secondary. One method is to put the 24V to a bridge rectifier, with the negative diode side to "ground". That then gives the center tap as a 12V DC tap.
ie: (example at bottom is for 600/300V, but works for 24V/12V). Hope it shows ok...

https://el34world.com/Forum/index.p...ion=dlattach;topic=25003.0;attach=78693;image

SAGOR is exactly correct!! I have done that for industrial machines that ran with no problems, until they became obsolete years later. The only limit is the total power drawn must not exceed the transformer ratings. And the diode current ratings must be adequate.