Depending on context, protector can be translated as:
Beschützer
Panzer, e.g. Brustpanzer - chest protector
Schutz, e.g. Gewebeschutz - textile protector
Schutzschalter, e.g. Stromschutzschalter - surge protector
Schützer, e.g. Knieschützer - knee protector