TMS320F28069M: Motor has sometimes Current Overshoots when start spinning the Motor

Hi guys,

My Motor is an 230 BLDC Motor. When I set an Motor Speed the Motor has sometimes Current Overshoots at Startup.

Then comes the protection circuit triggers from the electronics

I use the PROJ_LAB05e with this Motor Parameters.

#define USER_SYSTEM_BANDWIDTH                        (10.0)
#define USER_MOTOR_TYPE                                        MOTOR_Type_Pm
#define USER_MOTOR_NUM_POLE_PAIRS              (4)
#define USER_MOTOR_Rr                                              (NULL)
#define USER_MOTOR_Rs                                             (1.38470221)
#define USER_MOTOR_Ls_d                                          (0.0027)
#define USER_MOTOR_Ls_q                                           (0.0027)
#define USER_MOTOR_RATED_FLUX                          (0.8508)
#define USER_MOTOR_MAGNETIZING_CURRENT   (NULL)
#define USER_MOTOR_RES_EST_CURRENT            (6.0)
#define USER_MOTOR_IND_EST_CURRENT             (NULL)
#define USER_MOTOR_MAX_CURRENT                     (40.00)
#define USER_MOTOR_FLUX_EST_FREQ_Hz            (5.0)
#define USER_MOTOR_MAX_SPEED_KRPM              (3.0)
#define USER_SYSTEM_INERTIA                                    (0.06704008579)
#define USER_SYSTEM_FRICTION                                  (-0.09187704325)

With Lab5c i learned the Inertia und Friction Values.
Is this correct that Friction can be negativ ?

Can you give my an advice why i become sometimes overshoots at startup.
 
Thanks

Alex