The Design Of Three-Phase Current Motor Protect And Monitor System

The electromotor as the power device is widely used in the power plants and industrial enterprises. With the development of the economy in our country, the electromotor will continue to be used in the field of oil, chemical industry and metallurgy, etc. So, it is very important to research the field of electromotor protection and produce electromotor protector with good characters.The meaning of the electromotor protection , present development and the existing problems are introduced in this paper, the general faults of the electromotor running is described .According to the characters of the various fault , the mathe model is established, and the theory and arithmetic of the electromotor sequencing protection are put forward.The construction of th hardware system for electromotor protector and the characteristics of the AVR high-speed singlechip are described in detail, some kinds of the general field bus and ModBus field bus used in the electromotor protector are discussed. A real-time monitering and intelligent pretecting system for three-phase current electromotor are developed . the system is based on the computer , the PLC or touchsecreen as the host computer , the intelligent electromotor protector as the nodes ,building the communication nets with the ModBus field bus ,and monitering and protecting the working status of the electromotors in real time.According to the ModBus field bus ,The host computer can moniter the protectors, get the working datas of the electromotors and start or stop the electromotors with the protectors. The protector is based on the AVR high-speed singlechip as the CPU, measuring the three phase voltage and current with AC sampling, figuring out the negative sequence current and zero sequence current and protecting thelectromotors. The methods of the assignment the singlechip CPU and the establishment ModBus communication prototol are discussed in this paper, the monitering software of the host computer is authorized with the Visual Basic senior language, some interface and resource procedure codes are offerd in this paper.At last, the effective methods and datas are offerd in this paper ,the validity and utility of the system are tested.