[christianw.]

Wenn dein Trafo die Polyfuse heizt gibt das m.E. eine Verschiebung des Trip-Punktes.

Blode Frage, was willst du mit einer 5A Polyfuse auf der Sekundarseite? Die Teile sättigen weich, wenn also z.b. 8A gefordert sind, erhöht sich der Innenwiderstand des Netzteils. 

Zitat:Temperature rating: the useful upper limit for a PTC is generally 85° while the maximum operating temperature for fuses is 125°C. Both devices require derating for temperatures above 20°C and a representative curve for that purpose is provided.

The PTC Rerating Curves located on data pages, should be consulted for the proper rerating of the various PTC series at ambient temperatures other than 20°C.

Additional operating characteristics can be reviewed by the circuit designer in making the decision to choose a PTC or a fuse for overcurrent protection.