求翻译：主要介绍了直流电动机PWM的系统原理，设计了调速系统，分析了直流脉宽调速系统的机械特性，最后建立了PMW控制与变换器的模型是什么意思？

Introduces the system principle of PWM DC motor, speed control system designed to analyze the DC PWM speed control system of the mechanical properties, and finally established the model PMW control and converter

The principal introduced the DC motors PWM systems theory, and design the speed control system to analyze the DC pulse width speed control system has been established for mechanical properties, and finally the model PMW control and converters

Mainly introduced the direct current motor PWM system principle, has designed the velocity modulation system, has analyzed the direct-current pulse width velocity modulation system physical characteristics, finally has established the PMW control and the converter model

Main DC motor PWM system principle was introduced, designed the speed control system, analysis of mechanical property of DC PWM speed regulating system, and finally established the PMW converter and control model

正在翻译，请等待...