基于PLC的三相异步电机变频调速系统的设计毕业论文重庆科技学院.docVIP

高等教育自学考试本科毕业论文 基于PLC的三相异步电机变频调速系统的设计 高等教育自学考试本科毕业论文 基于PLC的三相异步电机变频调速系统的设计 摘 要 随着科技的进步，电机的运用已经深入到各行各业的各个领域。而现今也是一个资源高度消耗造成能源匮乏的时代，在这个时候考虑如何让其在高可靠性的同时又有效的节约能源耗费提高自身的效率，这不仅可以使企业的生产成本降低，而且对于社会的可持续发展有着重要的意义。本文所讨论的是利用PLC控制的三相异步电机变频调速的基本原理与实现方法。三相异步电机一般的调速方法有：降压调速，转子回路串电阻调速，变极调速，串极调速，变频调速等。但是这些调速方法都有着各自的缺点，降压调速的调速范围很小，没有多大的实用价值；转子回路串电阻调速不利于空载或轻载调速，效率低，经济性差；变极调速调速的平滑性差；串极调速的控制设备复杂，成本高，控制困难。所以调速性能至少需从两方面考虑。第一，应从节能和提高效率的角度考虑，应将损耗在转子附加电阻上的能量吸收，转化成别的有用的能量或反馈到电网，以提高传动系统的效率。第二，应从高性能调速要求考虑，应用控制理论，将其组成闭环调速控制系统，满足调速精度、动态响应等各项指标的要求。 综上所述，利用PLC控制的变频调速系统，是使三相异步电动机实现高性能高效率调速的有效办法。通过改变定子绕组的供电频率f来实现，当转差率s一定时，电动机的转速n基本上正比于f。很明显，只要有输出频率可以平滑调节的变频电源，就能平滑的调节异步电动机的转速。 关键词：变频调速，PLC，异步电机  The three-phase asynchronous motor variable frequency speed regulation system based on PLC design Abstract Human being is seriously threatened by exhausting mineral fuel, such as coal and fossil oil. As a kind of new type of energy sources, solar energy has the advantages of unlimited reserves, existing everywhere,using clean and economical .But it also has disadvantages ,such as low density,intermission,change of space distributing and so on. These make that the current series of solar energy equipment for the utilization of solar energy is not high. In order to keep the energy exchange part to plumb up the solar beam,it must track the movement of solar. In this paper, the solar tracking system of the mechanical part and control system part are designed. Mechanical structure mainly includes the main spindle, stepping motors, gears and gear ring, and so on. When the suns rays has a deviation, small gear are rotated by stepper motor according to the control signal from MCU. And the large gear and main spindle is rotated by small gear in order to track to achieve the level direction. At the same time, another small gear is rotated by another stepper motor according to the control signal.And the large gear and the solar panels are rotated by the small gear in order to track to achieve the vertical direction.