The null point shift in three-phase load is studied by using the equation of circumference and an arc and the changing law of the null point shift is discussed qualitatively.

• 运用圆弧方程和圆图分析了三相负载中点位移的特性，定性讨论了中点位移的变化规律，这对加深理解中点位移和实际应用有参考意义.