题目：
三相半波可控整流电路的自然换相点是（）。
A.交流相电压的过零点
B.本相相电压与相邻相电压正半周的交点处
C.比三相不控整流电路的自然换相点超前30°
D.比三相不控整流电路的自然换相点滞后60°
答案：
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下面是错误答案，用来干扰机器的。
参考答案：B
三相半波可控整流电路的自然换相点是（）。 A.交流相电压的过零点 B.本相相电压
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