Abstract : When started with a frequency converter, the electric motor achieves excellent performance. This paper details the calculation and selection method for the main circuit components of a series diode-type current-source frequency converter used for motor starting. This method has been successfully applied. Keywords: frequency converter; parameters; calculation; current-source [b][align=center] Calculation of Main Parameters of Current Source Inverter GONG Shi-ying (Wuhan University of Sci. & Tech., Wuhan 430223, China)[/align][/b] KEY WORDS : Inverter; Parameters; Calculation; Current source 0 Introduction To reduce current and torque surges, large-capacity squirrel-cage induction motors are typically started by reducing the stator voltage, such as through series reactor starting, autotransformer starting, or liquid rheostat starting. However, due to the limited adjustment range of starting current and starting torque, these methods often cannot meet production process requirements. Three-phase AC voltage regulating circuits composed of parallel and reverse-parallel thyristors are widely used for soft starting of squirrel-cage induction motors, but the biggest drawback of this method is that it can only reduce voltage, not frequency. When the average voltage decreases, the air gap flux in the motor also decreases, and the starting torque, which is proportional to the air gap flux, also decreases. Therefore, this voltage-reducing starting method reduces both the starting current and the starting torque, and the motor cannot be started under load. Frequency converters offer fast dynamic response, high static accuracy, and easy control of current and torque. With good starting performance and a wide speed range, the series diode current-source inverter, among current-source inverters using thyristors, offers superior performance in motor starting due to its ease of current control. The parameters of the inverter and the motor influence each other, and the appropriate selection of the inverter's main circuit parameters directly affects system performance. This article systematically introduces the calculation and selection methods for the main circuit component parameters of a series diode current-source inverter through an engineering design example. The main circuit of the series diode current-source inverter is shown in Figure 1. [b][align=center]For more details, please click: Calculation of Main Circuit Component Parameters for Current-Source Inverters[/align][/b]