The pantograph-catenary system is a critical component for trains required to run at higher speeds. The pantograph often includes nonlinear characteristics and the scope of this work is to investigate if nonlinear dynamic phenomena can occur in an existing design. A model of a pantograph suspension subsystem has been developed according to physical parameter values of the head suspension of the Schunk WBL88/X2 pantograph, providing electric power to the Swedish high-speed train X2. Studies of the system response for different force excitation show both harmonic, subharmonic and chaotic behaviour for the investigated parameter regions.