试画出既能使三相异步电动机正、反连续运行，又能在正转或反转时点动的控制电路，要求具有过载、短路、欠压（失压）保护。

【参考答案】

用SB₄作正转点动，SB₅作反转点动，画出控制电路如图所示。
图中：......

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