1_Is there any king of Y capacitors for DC lines? I only can find AC line Y capacitors which as rates for 250V etc.
2_Can i use Y caps after AC to DC converter at 24V voltage stage? Because i can only intervente after AC to DC converter stage.
3_Should i put Y caps on both of 24V line and 0V line. I am asking this question because i think the noise is coming from only 0V line and i am thinking about putting Y cap only between 0V and earth ground.
"X" and "Y" capacitors are capacitors that are specially designed and manufactured for putting across the 230V AC mains. They are designed to fail in a non lethal way.
Now if you want to get rid of noise on a 24V DC line , you can use any capacitor rated for greater then 24V.
Frank