【作者】 曲弋；

【导师】 蔡志远；

【作者基本信息】 沈阳工业大学 ， 电气， 2002， 硕士

【摘要】 电动机在运行过程中往往会因绕组温度过高而影响其绝缘性能，为此要求热保护电器能及时给予跳闸保护。随着微型计算机技术、电子技术和信息处理技术的发展，单片机式电动机热保护器正迅速发展，并越来越受用户青睐。 目前，发展单片电动机热保护器的关键是探索合理的热过载保护模型。为研究电动机的热特性，本文以一台2.2kW的三相笼形异步电动机为研究对象，预先在其内部埋设了6枚热敏电阻。为实现测试过程的自动化，本文研制了一套微型计算机控制的自动测试装置。利用该装置测试了被试样机在不同负载率下的发热和冷却过程，并把实际测试结果同现有的电动机热保护标准和热过载保护模型作了对比，在分析和讨论了各种标准和热过载保护模型建模机理的基础上，得出了最佳的、可供单片机式热保护器使用的热过载保护模型，即双时间常数的指数发热和冷却方程。 在确定了热过载保护模型的基础上，本文设计了一单片机式电动机热保护继电器。该电器以PIC16F873单片机为核心，配以检测电路和接口电路等外围电路，体积小、可靠性高，具有参数整定、状态显示和故障诊断及处理等多种功能。运行结果表明，本文所研制的单片机式热保护电器能较好地动态跟踪负载变化，其热保护特性能较好地与电动机的允许过载特性相匹配，有一定的工程实用价值。更多还原

【Abstract】 During operating, the insulation properties of motors will decrease due to over temperature of stator winding, thus thermal protectors are needed in order to protect motor. With the development of microcomputer and electronics as well as information processing technique, motor protectors with single-chip have came forth, and been favored increasingly by users.In order to develop motor protectors with single-chip, it is important to research a reasonable overload protection model. In this paper, a 2.2 kW motor is used for researching thermal property. 6 thermistors are encased in stator winding, thus the temperature of stator winding can be measured. The automatic measure device with microcomputer is designed. The heating and cooling process are measured by means of the above device. The experimental results are compared with the existing criterion and model so as to obtain the optimal overload protection model, viz. exponential heating and cooling equations, which can be used for protecting motors.Based on the selected overload protection model, a thermal protector with single-chip is designed in this paper. The protector uses PIC16F873 single-chip as the center, adds measuring circuit and interface circuit etc. And the protector has the features of small volume and high reliability as well as multi-functions such as setting parameters and displaying status and diagnosing faults so on. According to the operation condition, it is shown that the protector presented in this paper can duly follow the motor’s load fluctuation and capitally match with motor’s tolerance overload characteristic, thus it is valuable to be actually used.更多还原