轮机英语教学课件(24)-Switchboard.ppt

1、Lesson 24 Switchboard配电板1.Focus2.Vocabulary3.Analysis of long and difficult sentences4.Review questions5.Choices related to the competency testFocus:1.Different kinds of switchboards and their characteristics and application2.ExercisesVocabularymain switchboard emergency switchboard section board di

2、stribution boardopen type deadfront type operating handle compare with main bus-bar emergency generator insulation breakdown earth fault TEXT：SWITCHBOARDSwitchboard:to control and distribute the electrical energy generated by generators.Main switchboard:to connect the main generators Emergency switc

3、hboard:to connect the emergency generator or battery Section boards/sub-boardsDistribution boardsequipmentequipmentequipmentEmergency generatorsBatteryEmergency switchboardEmergency equipmentDistribution boardSection boardSection boardDistribution boardequipmentMain generatorsMain switchboardShore p

4、owerEmergency equipmentSwitchboard for A.C.system and D.C.system vOpen type switchboard vDead front typeOpen type switchboard nall the essential switch gears are exposed on the front of the panel.nNotes:Open type switchboard are generally not permissible for A.C.system.Dead front type nall the live

5、parts are installed behind the panels and only the operating handles and instruments are on the front.n Two patterns:One having manually operated switches and circuit-breakers with the handles on the front of the panel and the live parts at the fear.The other having electrically operated circuit-bre

6、akers operated by push bottoms on the front of the panels.Generally the panels are interlocked with isolators,so that the panels can be made dead before the doors are opened.Notes:A.C.switchboard is usually smaller and lighter than D.C.switchboard.Meters and equipments on the front of the switchboar

7、d:Meters D.C./A.C.ammeter voltmeter circuit-breaker tipping devices A.C.frequency meter synchroscopes wattmeter voltage and current transformers ammeter switch voltage regulator Equipments Bus-bar is continuously alive throughout the life of the ship.Sentence analysis:1.In small equipment,particular

8、ly in small cargo ships,most of the motors can be fed directly from the main switchboard,but as the size and multiplicity of services increase,it becomes necessary to reduce the number of outgoing circuits on the main board.小型设备，尤其在小型货船上，大多数电动机都直接由主配电板供电，但随着设备的尺寸和用途多样性的增加，就有必要减少主配电板上输出电路的数量。该句为由转折连词

9、but连接的并列句组成。第一分句的主语是most of the motors谓语是be fed;from the main switchboard 和In small equipment,particularly in small cargo ships分别为方式状语和地点状语。第二句中的as从句为条件状语，It为主句形式主语，真正的主语是to reduce the number of outgoing circuits;on the main board 是circuits的后置定语。2.Switchboards may be of the open type in which all th

10、e essential switch gears are exposed on the front of the panel,or of the deadfront type in which all the love parts are installed behind the panels and only the operating handles and instruments are on the front.配电板可以是开式的，即所有重要的开关都暴露在面板上，或者是不带电式的，即所有的带电部件安装在面板背面，只有操作手柄和仪表在上面。该句中of the open type 和or

11、of the deadfront type为并列的表语。in which 引导定语从句。第二个in which 引导的定语从句为并列句，第二分句的主语是handles and instruments.Reading material:A.Emergency generator supply In the event of a main generating system failure an emergency supply of electricity is required for essential services.Provide power for the driving motor

12、s of the emergency equipment and emergency lighting,navigation lights,and alarm system.Emergency switchboard normally consist of a generator control panel,a bus-bar and distribution panel and 24V,120V,and 450V distribution panels It is not usual for an emergency generator to require paralleling.B.Ma

13、intenance of electrical equipment Cleanliness is essential for good operation.The accumulation of dirt,moisture and oil deposits on electrical equipment will affect insulation resistance.The oil deposits should be removed if found.Regular insulation measurement.Electrical connection must be sound an

14、d any sign of sparking should be investigated.Totally enclosed machined should be periodically opened for inspection and cleaning.Parts subject to wear must be examined and replaced.The contactor contact surfaces of frequently used equipment should be regular inspections Note:Care must be taken to e

15、nsure isolation of equipment before any inspections or maintenance is undertaken.Review Questions1.On most large ships,what kind of switchboard is the emergency generator or emergency battery connected to?2.What kind of switchboard are the main generators connected to?3.What is a dead front switchboard?4.What is the difference between d.c.switchboard and a.c.switchboard?5.Prior to any overhaul work on electric equipment,what should we do?