PTC is wrong. Bi-metal is right.
Al has been kindly pointing that out several times, but I have planted a bad seed and it is growing.
PTC is a kind of conducting plastic that has a positive temperature coefficient which is the secret sauce that allows it to be used as resetting breaker for current. Basically the more current it conducts the hotter it gets the hotter it gets, the higher the resistance (the positive coefficient, get it) the this causes more heat build up until you get a cascade where the resistance of the PTC is so high that it only conducts a very small amount of current that (hopefully) allows the fault to clear while the device it protects is kept from catching fire or melting or whatever. PTC's literally revolutionized the automotive electronics business about 20-25 years ago.
BUT... ...at higher currents, PTCs become problematic.
Bi-metal becomes more competitive at currents above 20-25Amps.
Bi-metal is just what it sounds like two types of metal stuck together (usually not literally stuck together but they are more often hot formed together). When the strip of bi-metal gets hot, one metal expands more than the other so the strip bends. This bending action is used to open a switch contact.
SO.... FP uses a bi-metal thermal switch to protect the motor.
Please make a note of it.
Joe J.
P.S. Thanks to Al for his encyclopedic (wikipedic?) knowledge of all things FIRSTian.