What does 'thermally protected' mean on the nameplate of a motor?

That means that there´s a switch which protects the motor of overheating. For instance if on the nameplates is a marking: IsoKl. F it means that the motor is protected up to 155°C. There´s a Thermoswitch on every phase (3) to protect the insulation. The two cables are a little bit thinner than the others.