A solid state circuit breaker (100) is disclosed, which includes a solid state switch (SW), an inductor (L) in series connected with the solid state switch (SW), and a fault detection circuit (1). The solid state switch (SW) has a gate electrode (g), a source electrode (s) and a drain electrode (d). The fault detection circuit (1) is configured for detecting health status of the solid state switch (SW) and identifying faulty type of the solid state switch (SW) in the condition that the solid state switch (SW) occurs fault based on one or more of a measured voltage (V 1 ) of the solid state switch between the source electrode (s) and the drain electrode (d), a measured voltage (V m ) of the inductor, a reference voltage (V r ) and a switching control signal (S g ) provided to the gate electrode of the solid state switch. A motor driving system (200) is also disclosed.