变频器接线时应注意哪些问题？
参考答案：
①输入电源必须接到R、S、T上，输出电源必须接到端子U、V、W上，若错接，会损坏变频器。②为了防止触电、火灾等灾害和降低噪声，必须连接接地端子。③端子和导线的连接应牢靠，要使用接触性好的压接端子。④配完线后，要再次检查接线是否正确，有无漏接现象，端子和导线间是否短路或接地。⑤通电后，需要改接线时，即使已经关断电源，也应等充电指示灯熄灭后，用万用表确认直流电压降到安全电压（DC25V以下）后再操作。若还残留有电压就进行操作，会产生火花，这时先放完电后再进行操作。
| 阅读下面短文，根据所读内容在表格中的空白处填入恰当的单词。注意：每个空格只填一个单词。 | ||||||||
| Few Americans stay in one a place for a lifetime. We move from the city to the suburbs (郊区), from high school to college in a different state, from a job in one area to a better job elsewhere, from the home where we raise our children to the home where we plan to live in retirement. With each move we are forever making new friends, who become part of our new life. For many of us the summer is a special time for forming new friendships. Today, millions of Americans go on vacation abroad, and we go not only to see new sights but also in those places where we don't feel too strange with the hope of meeting new people. No one really expects a vacation trip to produce a close friend, but the beginning of a friendship is possible. Surely in every country people value friendship. The word "friend" to American people can be applied to a wide range of relationships-to someone one has known for a few weeks in a new place, to a close business companion, to a childhood playmate, to a man or a woman, or to a trusted colleague. There are real differences among these relations for Americans a friendship may be shallow, casual, situational or deep and lasting. But to a European, who sees only our surface behavior, the differences are not clear. As Europeans see it, all kinds of "friends" flow in and out of Americans' homes with little ceremony. They may be parents of the children's friends, house guests of neighbors, members of a committee, business associates from another town or even another country. Coming as a guest into an American home, the European visitor finds no obvious landmarks. The atmosphere is relaxed. Most people, old and young, are called by first names. Americans' characteristic openness to different styles of relationship makes it possible for us to find new friends abroad with whom we feel at home. | ||||||||
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