Can I exchange my power beats for another set? The one I have is defective, had them fit 3 yrs.

The support article you came here from should provide you with the steps needed to try to resolve this issue. Have you tried them all yet? If so, and they didn't help, I suggest that you contact Apple Support directly. To do so, simply select the "Get Support" link in the upper right-hand side of this forum's web page.

However, if you are actually asking, can you get them replaced for free, then the article that Rudegar has provided you should provide you the answer.

you can try reading Service And Warranty (beatsbydre.com)

and or contacting apples support Apple Support