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181·电流继电器是用于电动机的过载及短路保护，直流电机的磁场控制或失磁保护等场合。
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触头的初压力可以防止触头接触时的碰撞。
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触头的开距必需保证触头经的住电压的冲击而不被击穿。
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触头的开距、超程、压力都是检修中必须进行检测的主要参数。
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真空接触器易出现电弧电流过零前就熄灭，出现截流现象，因而在电感电路中产生过电压。
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接触器在电力机车上是用来频繁地接通或切断没有负载的主电路。
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接触器在电力机车上是用来频繁地接通或切断没有负载的主电路。
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稳压二极管是二极管的一种，它在电路中的使用方法和普通二极管一样。
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硅整流管上所标电压为反向不重复峰值电压。
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硅整流管的额定电流，指的是它可通过的最大电流。
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在使用’TY型绝缘检测仪时，泄漏电流选择开关先放到最大量程挡
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’rz型接触电阻检测仪配有专用测笔，测笔与仪器之间的接线可长达10余m，测试时被测表面与测笔之间的接触电阻并不影响测试数据。
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’rY型绝缘检测仪两根高压绝缘导线的一端各插至仪器面板上的高压插座内，有红色鳄鱼夹头的一根插入“一”端，有黑色鳄鱼夹头的一根插入“+”端。
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’F-Z-1型接触电阻睑测仪测量电感性元件时，应在被测元件两端串接电阻器。
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司机控制器是利用控制电路的低压电器来间接控制辅助电路的电气设备。
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’rKSl4A型司机控制器手柄在“前”或“后”位时，手轮只可转向“牵引”区域。
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’rKSl4A型司机控制器手柄在“制”位时，手轮只可转向“制动”区域。
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’rKSl4A型司机控制器手轮在“0”位时，手柄只可移向“前”、“后”、“制”位。
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‘TKSl4A型司机控制器手轮在“牵引”区域时，手柄只能在“I”、“II”、“Ⅲ”位间移动，或被锁在“后”位。
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TKH4型位置转换开关中，每组两触指应与安装板垂直，相互间不应有卡滞或平行现象。
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TKS6E型司机控制器有：“”后、“前”、“制”、“I”、“II”、“Ⅲ”6个位置。
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当ss9型电力机车速度达到119km／h时，牵引电机电压限制值为l 100v。
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SS9型电力机车微机控制装置设A、B组，采用转向架独立控制。
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电力机车作为牵引动力，它的牵引特性主要取决于电动机的工作特性。
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SS4型电力机车发生主接地故障后，如运行途中不能及时处理而需要维持机车运行时，可以用故障开关将接地继电器切除。
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一般带有传动件的电器要进行过电压保护。
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和单臂受电弓相比，双臂受电弓结构对称，侧向稳定性好，但结构复杂，调整困难。
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A. such an important and helpful job B. so important and helpful work
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21. —The 2010 World Expo which will last 184 days will be held in Shanghai on May 1st.
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25. — David, look at the man in white over there．Can you tell me _______ ?
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( ) 26.With help from a Mr. H, you can__________.
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( ) 27. A PENGO WATCH CONTROL can help you to ______________.
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( ) 28. You can get your Mr. H for___________.
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( ) 29. When was canned food invented?
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( ) 30. After the trip to the Arctic, Clarence Birdseye invented ____________.
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( ) 31. Changes in weather _____________ in Willis Carrier's company.
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( ) 32. According to the passage, which of the following may lead to inventions?
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( ) 33. What is the writer's main purpose（目的）in writing this passage？
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B．To tell people what kind of person his father was．
C．To tell the readers what present he got from his father．
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( ) 34. Why did the father not ask his son not to do this and do that？
A．Because he felt quite confident of his son．
B．Because he was born from a poor family．
C．Because he was a man of few words．
D．Because he didn't want to be much too strict with his son．
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( ) 35. What would someone learn from this passage？
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( ) 36. What may be the proper Chinese for the underlined part in the passage？
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( ) 37. The Chinese Yellow Sea Wetlands are in the _______ of China．
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( ) 38. Usually the weather in the wetlands is _______．
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( ) 39. The World Wetlands Day is on _______．
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( ) 40. We must protect wetlands because _______．
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) 1. —Is it far from here to the bank?
—Not very, only________．
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— Thats great!
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3. Yesterday Tommy walked past my table and ______ my bowls and dishes.
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A. knocked off B. took off C. showed off D. turned off
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