本指南描述了测量感应低压（1000 V及以下）测试电路功率因数时使用的三种方法。这些方法可在任何频率下使用；然而，表中的值专门用于60 Hz测试电路。这些方法如下:a）比率法；b） 直流衰减法；c） 相位关系法。 表1列出了用于不同测试电流水平和不同功率因数水平的首选方法。虽然本指南主要用于低压测试电路，但所讨论的方法也适用于更高的电压。

This guide describes three methods used in the measurement of the power factor of inductive low-voltage (1000 V and lower) test circuits. These methods may be used at any frequency; however, the values in the tables are specifically for 60-Hz test circuits. These methods are as follows: a) Ratio method; b) DC decrement method; c) Phase relationship method. Table 1 lists the preferred methods to be used for different levels of test currents and for different levels of power factor. While this guide is primarily intended for use on low-voltage test circuits, the methods discussed are also usable at higher voltages.