A Novel Coupled Auto-transformer and Magnetic Control Soft Starter for Super Large Capacity High Voltage Motor

The start current can reach up to as high as 4–7 times of the motor's rated current when high voltage motors start directly. For super large capacity motors (voltage above 6 kV, power above 10000 kW), the direct start current could reach 5000 Ampere or more [1]. Such large start current will not only have a huge impact on the motor itself but also cause a sudden decline of the grid voltage [2], [3]. In order to resolve this issue, a novel coupled auto-transformer and magnetic control (CATMC) soft starter method was proposed in this paper. The new structure of CATMC soft starter combines the two functions of the auto-transformer and the magnetic control reactor (MCR) through ingenious electric and magnetic circuit design. Hence the start current is reduced in two ways and the structure becomes more compact and flexible.