A novel soft start method of super large capacity high voltage motor

The large current generated by starting directly of super large capacity and high voltage induction motor would have a huge impact on the grid as well as the motor itself. The variation of the power factor and electromagnetic torque during direct start of motors with different capacity and voltage levels are obtained. Aiming at the problem that the secondary impact of auto-transformer starter is too large and the cost of magnetic control starter is too high, the auto-transformer and magnetic control soft start method of super large capacity and high voltage motor is proposed and the basic working principle is analyzed. The calculation formula of cost for magnetic control soft starter and auto-transformer and magnetic control soft starter is deduced, and specific examples are analyzed and compared. It is concluded that the choice of auto-transformer with appropriate tapping ratio can greatly reduce the cost of auto-transformer and magnetic control soft starter compared with the other one. Finally, the simulation and experiment results show that the start method can effectively avoid secondary current impact and constrain the motor starting current to less than 2.5 times the rated current.