I'm developing a model in MATLAB of BLDC motor with 6-step commutation, for testing purpose considering only current control loop of cascade control, where reference current is given as input to the model consist of PD controller, PWM technique and sensor unit , here on the load side of the motor constant speed is given as load input(angular velocity) along with rotor inertia kindly help to understand why the output torque is negative (since current is proportional to torque, current is also negative)

At 30 rad/s torque output is good

At 300 rad/s torque is negative

Max operation speed of motor is 366 rad/s