Permanent magnet synchronous machine

Hi, I am using a permanent magnet synchronous machine as a generator for my wind turbine. I am giving a constant torque input but the rpm of the machine increases and it does not damp. Due to which the output voltage is also increasing. I am not using a preset model for the simulation. I am giving the Flux linkage established by magnets (V.s) to be around 0.111. I am a newbee to simulink and also to Permanent magnet synchronous machine. Any help would be greatly appreciated.