Abstract : When a medium-voltage motor is started directly at its rated voltage, the large current can disrupt the stability of the power grid, causing other equipment on the same grid to malfunction. This paper introduces several starting methods, new starting technologies from abroad, and medium-voltage frequency converters. Medium-voltage frequency converters are suitable for starting medium-voltage motors. Although they are more expensive, they offer high cost-effectiveness, meeting the requirements of soft starting, frequent starting, and no impact on the power grid. Keywords : Medium-voltage motor; Soft start; Frequency converter 0 Introduction When a squirrel-cage motor is started directly at its rated voltage, the current is large, reaching 5 to 7 times the rated current. This is especially true for medium-voltage motors with voltages of 3 to 10 kV, which generally have large capacities. Starting this motor causes a sharp drop in grid voltage, disrupting grid stability and causing other equipment on the same grid to malfunction. The large current during direct full-voltage starting generates significant impact forces and Joule heat in the stator coils and rotor squirrel-cage bars, damaging the winding insulation and reducing the motor's lifespan. The starting torque during direct full-voltage starting is approximately twice the rated value. The hazards of large impact forces during startup are: for gear transmission equipment, it will accelerate gear wear and even break the gears; for belt transmission equipment, it will aggravate belt wear and even break the belt; for water pumps, it will create a water hammer effect and damage the pipeline. Therefore, solving the starting problem of squirrel-cage motors is of great significance. [b]1 Commonly Used Starting Methods in the Past 1.1 Increasing the Power Grid Capacity[/b] To meet the power requirements of large-capacity motors during startup, people used to often increase the capacity of the power grid itself. For example, in the case of an independent transformer supplying power (for power), the selected transformer capacity was greater than 20% of the motor power. This can solve the problem of excessive starting current, but the load is relatively light during normal operation. The transformer operates under light load, resulting in wasted energy. [b][align=center]For more details, please click: Medium-Voltage Motor Starting Technology[/align][/b]