电机标幺值系统研究

Research on Per Unit System of Electric Machines

标幺值是"电机学"课程的重要内容之一。本文提出以频率、容量、电压、绕组有效串联匝数和每极电枢表面积为电机基本物理量来定义基值,从而导出电枢相关各物理量的基值以及基于磁通不变性的直流励磁和异步转子回路各物理量基值的确定方法,从而形成完整的电机标幺值系统。该标幺值系统具有与相数和绕组连接方式无关的特点,保持基本方程形式的不变性,并简化了电机特性表达式,凸现了电机的本质特征,有助于激发学生研究电机的兴趣。

Per-unit concept is one of key contents of Electric Machinery course. Frequency,capacity,voltage,ef-fective series turns and area of armature per pole defined as fundamental quantities are proposed in this paper. Their base values are defined as the rated values or structure parameters of electric machines. Other quantities re-lated to armature windings are further determined. Based on invariance of the main flux,the base values of quanti-ties for the windings like DC excitation and asynchronous rotor with different frequencies are obtained. Therefore,a set of per unit system is completely built up,which is independent of phase number and connection modes,keeps invariance of equations,reduces the expressions of characteristics of electric machines,such that the nature of elec-tric machines is outstanding and the students are interested in this phase.