Motor starting, including the motor access to the power from the rotor to reach the full speed of the whole process. Motor should be with a sufficiently large locked rotor torque and minimum torque and to drive mechanical load quickly starting, and reaches the rated speed and normal work; at the same time should have sufficient for the maximum torque, to ensure certain overload capacity. And for blocking the current (or blocking to the power), should be limited, so as to avoid the power supply has a large voltage drop and affect the normal operation of other electrical equipment connected to the same power supply. In addition, the starting current is too large, it will cause the motor winding overheating and subjected to too large electromagnetic force impact. Starting requirements motor is allowed in cold continuous starting twice (between the two starts the motor should be natural stop), or in rated operation in hot state starting once, and the provisions of the driven load inertia value.