Abstract : This paper analyzes the AC power supply, rectification stage, inverter stage, and motor of a practical motor system as a whole. For ease of analysis, conducted interference is divided into common-mode interference and differential-mode interference. The main common-mode and differential-mode interference channels in the PWM motor drive system are analyzed. Since the path of conducted interference is greatly related to the turn-on and turn-off of the upper and lower bridge arm IGBTs, the propagation paths of common-mode and differential-mode interference under different IGBT switching states are analyzed. The consistent conclusions drawn from three different simulation results demonstrate the correctness of the mechanism analysis in this paper. Keywords : PWM motor drive, conducted interference, mechanism analysis 1. Introduction Since PWM technology is applied to motor drive systems, the power converter uses switching devices such as MOSFETs, IGBTs, and turn-off thyristors. In order to obtain better motor system control performance indicators, the operating frequency of the switching devices is getting higher and higher. Large voltage and current change rates are generated at the moment of switching and turn-off, which is the cause of strong electromagnetic interference (EMI), far exceeding the allowable values ​​specified by current electromagnetic compatibility standards. The electromagnetic interference generated is mainly propagated in the form of conduction. Mechanism analysis is the basis for establishing mathematical models. Therefore, mechanism analysis is of great significance for the study of conducted interference in PWM motor drive systems. Many domestic and foreign literatures have done some research in this regard. Literature [1] focuses on the serious common-mode electromagnetic interference problem caused by the high du/dt of IGBT to power electronic devices and analyzes the common-mode interference of Buck circuit in depth. Literature [2] establishes an input common-mode interference analysis model based on circuit theory, which is formed by the parasitic capacitance between the drain of the power MOSFET and the ground heat sink in a single-ended forward converter. I will not introduce them one by one here. The mechanism analysis in this paper studies the motor drive system as a whole, which is rarely found in the literature. Download the full text of the mechanism analysis of conducted interference in PWM motor drive system.