问题
单项选择题
笼形异步电动机常用的降压启动有（）启动、自耦变压器降压启动、星-三角降压启动。
A、串电阻降压
B、转子串电阻
C、转子串频敏
答案
参考答案：A
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笼形异步电动机常用的降压启动有（）启动、自耦变压器降压启动、星-三角降压启动。
A、串电阻降压
B、转子串电阻
C、转子串频敏
参考答案：A
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| At least thirty times Bobby had attempted to climb the big snowy mountain, but he had never reached the top. His friend old Peeper, who knew a lot about his failures, 1 Bobby to try again. He gave Bobby a pair of 2 and said, "If it starts clouding over, put on the glasses, or if your feet start hurting, put them on too. The glasses are very 3 . They'll help you." Bobby accepted the gift without much thought. The day came when he was to have another try. About two hours after he started, he felt his feet hurting. Then he 4 what Peeper had said, and put on the glasses. The pain was pretty bad, but 5 the sunglasses he could clearly see the snow-covered mountain top, so he went on. 6 , clouds were gathering. But this time Bobby could still see the 7 through the clouds. He kept climbing, leaving the clouds behind, forgetting his pain, and finally arriving at the top. It was certainly worth it. His feeling of 8 was extremely good, almost as great as that 9 view. The mountain below was surrounded by a sea of clouds. He couldn't believe that the clouds were as 10 as that, so he looked more closely at the sunglasses, and discovered the secret. Peeper had engraved (镌刻) the snow-covered mountain top on the sunglasses, 11 Bobby could see it when he was looking upwards! Bobby 12 that the only obstacle (障碍) to reaching the top had been losing 13 when he couldn't see the mountain top. He was thankful that Peeper had used that little 14 to help him see that his 15 was never impossible, and that it was still there, where it had always been. | ||||
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