Other people have asked this question and it seems like all are dual voltage.
[http://www.ifixit.com/Answers/View/18609/Is+PS3+Dual+Voltage|#1] [http://www.ifixit.com/Answers/View/20398/Playstation+3+CECH-2101A+dual+voltage|#2] [http://www.ifixit.com/Answers/View/22827/PS3+slim+dual+voltage|#3]
If you're really worried about it, you can always try taking it apart to double check. [[Device:PlayStation 3|PS3 Guides]]