PWM逆变电路多重化的目的有( )
A. 减小高次谐波
B. 减小低次谐波
C. 提高等效开关频率
D. 减小开关损耗
改变载波频率可改变PWM逆变器的（）
A. 开关频率
B. 输出信号波频率
C. 调制信号波频率
D. 一个周期内的pWM脉冲数
How does the "observer" carry out his assessment?
A. By wandering around the school and observing the teacher in a casual way.
By attending and evaluating the teacher's class in a formal way.
What does "dig into" mean here?
A. The lable rubs against the body in a painful way.
B. The lable pushes hard into the body and it makes Bradley bleed.
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