再论“因三相”正本清源——兼答姚南强先生

运用因明与逻辑的基本常识,对姚南强《再论“因三相”———对郑伟宏〈“因三相”正本清源〉的几点质疑》一文进行反质疑。     

断零的危害及其防范

在三相四线制配电回路中,有时会发生某一相或两相设备大量烧坏的情况,一般会被认为是三相负载不平衡造成三相电压不平衡引起的,这一结论显然是不完善的.必须考虑到三相不平衡负载状态下的零线断路同样可以造成这种危害.因此,防止三相四线制配电回路断零事故的发生,具有更广泛的意义.     

饰品之王从不足百元到亿万富翁

本文提出了采用DPS数字信号处理器并辅以单片机的无刷直流电动机的无位置传感器数字控制系统设计方案.该方案既可降低电路的复杂性,又可获得较高的性价比.     

“三相变压器联接组别”之创新教学

作者通过长期的实践探索,总结出一种关于三相变压器联接组别的新的判断方法--坐标法.本文具体讨论了这一方法的教学过程和相关理论.     

三相鼠笼式异步电动机的星—三角起动

三相鼠笼式异步电动机星-三角起动的控制线路用时间继电器完成，既可达到减小起动电流，又可防止电流短路事故，且延长了接触器的寿命。     

三相ZVS逆变器磁链轨迹

ZVS（zero voltage switching） PWM（pulse width modulation） inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every carrier period so that each power device can commutate when voltage of the main circuit＇s DC bus line is zero. To ensure the resonant circuit to operate properly, sawtooth with alternate slope （positive or negative） is used as carrier. But the time of zero voltage vectors with such PWM pattern is greatly different from traditional hard-switching PWM pattern. This paper discusses the locus of flux linkage under soft-switching PWM pattern by using space voltage vector. It is pointed out that, under the hard-switching PWM pattern, speed of flux linkage is adjusted by zero space voltage vector. When soft-switching PWM pattern is used, however, effective time of space voltage vector varies considerably, sometimes even without zero space voltage vector. Therefore non-zero space voltage vector has been used to make the speed of flux linkage locus equal to that of hard-switching PWM pattern. The cause of current distortion in soft-switching PWM inverters is also discussed. Based on the flux linkage locus circle, corresponding compensation methods are proposed. Experimental results show that the described method can effectively improve output current waveform of inverter.     

1600KW变频调速异步电机V—F参数的研究

本文介绍了1600KW 16P 6KW变频调速VVVF高压三相异步电动机驱动水泵负载变频调速时不同的V－F参数对电机的效率特性,功率因数特性的影响,提出了最佳V－F参数值。     

大型立式三相异步电动机新系列的开发

本文简要介绍了大型立式三相异步电动机新系列,指出了开关的关键是使用弹性支撑推力滑动轴承,并由此而采用的整机安装的结构及优点。     

农村配变三相负载不平衡运行后果分析与对策

分析配电变压器三相负载不平衡运行对县级供电公司用电管理的不良后果,并提出加强三相负载平衡管理的措施。