题目内容

Section One (Questions 13-17)• You will hear five short recordings.• For each recording, decide what the speaker's job is.• Write one letter (A-H) next to the number of the recording.• Do not use any letter more than once.• After you have listened once, replay each recording.

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Section Two (Questions 18-22)• You will hear another five recordings. Each speaker is leaving a message on an answering machine.• For each recording, decide what the main reason is for the phone call.• Write one letter (A-H) next to the number of the recording.• Do not use any letter more than once.

以下不属于电动机减压起动的是()。

A. 星形-三角形
B. 自耦变压器
C. 定子绕组串电阻
D. 延时起动

星角减压起动电路中采用互锁的原因是为了防止（）。

A. 短路
B. 断路
C. 通路
D. 无答案

电动机定子绕组接成星形时，起动电流为角形接法时的（）。

A. 3
B. 1/3
C. 2
D. 4