AN IMPROVED INSULARION SYSTEM FOR THE NEWEST GENERATION OF STATOR WINDINGS OF ROTATING MACHINES
Summary
In recent years there has been a distinct trend to utilize machines with indirectly cooled stator windings also for the higher ratings up to about 300 MVA with air cooling and about 450 MVA with hydrogen cooling This imposed new demands on the wellknown dielectric requirements as this is a key item when laying out the machine
This report describes the modified structure of an improved synthetic resin insulation MatadorPlus The most significant change was the introduction of powdered metaloxyde to the insulation structure used hitherto which it enable the thermals conductivity to be doubled The resulting characteristically changes are described relative to both short and long term behaviors of the insulation system
Based on the improved insulating qualities it was possible to reoptimize machine designs which is fundamentally demonstrated
Key words
Turbogenerator stator winding insulation system indirect conductor cooling thermal conductivity
1Introduction
Over the last decades the development of turbogenerators with indirect conductor cooling in the stator winding has led to ever increasing ratings Today machines are being built with this technology for ratings which just a few years ago were only possible with direct water or hydrogen cooling of the stator winding conductors
Air—cooled machines with ratings of up to 130 MVA were already in service by 1970With the development of gas turbines with larger unit ratings there is a trend today for aircooled turbogenerators with ratings of 300 MVA Hydrogen cooling in turbo generators permitted much higher unit ratings By the of the 50’s machines with indirect conductor cooling had been realized up to 250 MVA and today the limit is above 350 MVA
Compared with direct conductor cooling used on larger generators indirect cooling of the stator ending has the advantages that bar production is simple and less expensive the space needed for coolant flow with direct cooling is available for instance with water cooling
On the other hand indirect cooling requires that the heat losses generated in the conductors ate dissipated via the insulation wrapping on the stator winding bars which is a poor thermal conductor Depending on the case under consideration the temperature drop involved represent 20…40 of the total temperature rise
Besides the need to optimize the cooling technique on machines with indirect conductor cooling there was also the continuous requirement to improve the insulation system which helped to make this course in development possible The change in the 60’s from thermoplastic micafolium insulation system which helped to make thermoplastic micafolium insulations to epo
xy resin bases\d synthetic resin insulation led to considerable improvement in the physical and particularly in the dielectric properties of the insulation material A further step in the 70’s saw the introduction of total immersion impregnation also for large generator[45] The now further improved thermal conductivity allows a better dissipation of the winding heat losses and so a further increase in the ratings for indirect cooled machines
2Effect of the improved insulation system on machine design
21 Cooling principle
The laminated core is built up from varnish insulated electrical sheet segments and is subdivided into packets by radial duct spacers which form passages for the cooling gas flow In one of the most common designs the core is split up into different cooling zones whereby the cooling gas is led in through axial tubes located in the stator housing
The gas flows radically through the core ducts and absorbs the iron losses produced in the core and the copper losses generated in the stator bars The total temperature drop due to convection and thermal conduction The gas absorbs other heat losses before reaching the cooling surfaces of the stator winding and therefore already has a certain temperature which increases further after absorbing the iron and copper losses The winding copper losses must be dissipated by thermal conduction via the insulation In the regions of the cooling ducts heat transfer is by convection directly to the cooling gas flowing over the bar surfaces The larger portion of the winding losses in the active part is first transferred to the stator teeth and then dissipated to the gas flowing through the cooling ducts
22 Example of an aircooled turbogenerator
In a typical example dissipation by convection represents approximately 35 of the total temperature rise This portion could theoretically be reduced by increasing the velocity of the cooling gas However from a certain flow velocity heat transfer can hardly be improved upon and moreover in order to achieve higher flow velocity of the cooling gas However from a certain flow velocity heat transfer can hardly be improved upon and moreover in order to achieve higher flow velocities excessive fan pressures and consequently fan performances are necessary therefore this possibility does not offer much chance of reduction
The heat from the bar must be dissipated through the insulation by thermal conduction For a first approximation the temperature difference between the copper and the core can be taken as being
TiPdrs
Where PLosses to be dissipated
DInsulation thickness
SHear transfer area
RThermal conductivity
The insulation thickness is dependent on the rated voltage of the machine and therefore can nit be changed at all will Nevertheless the temperature difference between the copper and the core can be decreased thanks to an improved thermal conductivity of the insulation material It is therefore possible to increase the losses to be dissipated from the winding while maintaining the total temperature rise As an example the temperature difference between copper and core decreases while the convection part between copper and core decreases while the convection part becomes more dominant
The possible increase in rating depends on various parameters Increase voltage results in increased insulation thickness and therefore the temperature difference copper to core has a greater part of the total temperature rise The improved thermal conductivity of the stator insulation permits a possible increased rating for air—cooled generators in the r\range of 5…10 The rotor must be able to cover the higher back ampereturns produced by the stator by higher field ampere turns
D．C．MACHINE PRINCIPLES
1 Introduction
Direct current machines as a class include those machines that either produce or utilize direct current In either case the machine function as an energy conversion is from mechanical to electrical energy the machine is termed a generator If the conversion process proceeds in the other direction the machine is a motor There is no different principles involved in each case There principles are now discussed
2 Generator and Motor Action
Generator action is based upon the fact an emf (electromotive force) is induced in a conductor when the conductor moves in such a direction relative to a magnetic field that the conductor cuts the rate at which the conductor is moving relative to the magnetic field
Motor action is based upon the fact that a mechanical force is exerted on a currentcarrying conductor in a magnetic field The magnitude of the force is proportional to the product of the field strength and the current
There are definite relationships between the direction of the induced emf field and conductor motion in the case of a generator and the direction of the developed force conductor current and field in the case of a motor
For a generator the relationship is summarized in what is termed Flemings Right Hand Rule
Where a motor is being considered the basic rule is Flemings left Hand Rule
Where a machine operates as a motor or a generator in a given situation is largely independent of the machine conditions and parameters but depends on the direction of power flow between the machine and the electrical supply system
3 Generator Construction
The following descriptions and explanations apply to both motors and generators In the descriptions a material having good magnetic characteristics is one that can be worked at high values of flux density without saturation occurring and with a low hysteresis loss Where an alternative name for a component is common it is given in brackets
31 (Frame B Yoke ody)
This is the base on which the machine is built It has the following functions and characteristics
(1) The yoke completes the magnetic circuit comprising the poles air gaps and armature and gives a return path for the field flux
(2) Modern practice is to make the yoke of steel plate or cast steel of a good magnetic characteristic In this instance a low hysteresis loss is not important as the flux can be assumed to be constant
(3) The yoke also acts as a rigid frame to which piles and end shields are bolted and to which holding down feet are welded These are all an integral part of the yoke when the yoke is cast
32 Main pole System
(1) Each main pole is an assembly of steel laminations of good magnetic characteristics between 10 and 15 mm thick riveted together and of the same length as armature core
(2) Each pole provides a level seat for supporting a main field excitation coil The body of the pole is reduced to keep the mean length of turn of a main field coil to a minimum thereby reducing the coil resistance and losses
(3) Generally a given number of poles covers a given output range It will be appreciated that the number of poles will be an even number In general the larger the out put the greater the number of losses
33 Inter poles (Commutating Poles)
(1) Inter poles are fitted in the inter polar arc between the main poles and there are generally the same number of inter poles as main plows In some cases however only every alternate pole carries an excitation winding
(2) The poles can be either rectangular in shape and solid construction or alternatively they can be of laminated construction similar to the main pole
(3) Where steel bar parallel construction is used the inter pole coil held in position by clips or a similar device
34 Armature Core
(1) This is made up of iron laminations with very good magnetic characteristics and low iron loss since as will be seen later the armature winding carries an alternating current In addition each lamination is insulated to reduce eddy current losses further
(2) Slots are notched on the periphery of the core to take the coilsthe armature coils are fitted into these slots
(3) The cote is clamped firmly between two endplates and is keys to the shaft and on large machines pole vents are provided in the core to allow cooling air to pass through
35 Commutator
The commutator bars (or segments) are made of hard drawn or silvered copper held in place by steel vees which are rather of cast steel or machined from a bar The segments are insulate from the holding vees Insulation vees are made of mica In order to make the connections each bar is dotters in the riser portion and armature conductors ate then soldered in
Commutators must be machined to a very high degree of accuracy to ensure a smooth true surface for brushes to run on at all speeds
36 Brushes
The function of the brushes is to collect current from or supply current to armatures Depending on the purpose of the machine the brushes are made of special types of carbon Ideal carbon has long life negligible wearing effect on commutators and good commutating properties
37 Brushes Holder (Brush box)
The brush holder holds the brushes is the brush in position in contact with the commutator allowing it to slide up and down but without allowing side movement In order to maintain the correct pressure aspiring arrangement presses the brush firmly on to the commutator
The brush holder is clamped to the rocker arm
38 Brush Rocker
The brush rocker consists of two parts a rocker ring and a rocker arm The rocker arm is clamped into position on to the rocker ring and is insulated from it The bruch rocker generally fits on a spigot inside the end shield enabling the brushes to be rotated round the commutator until the best brush position is obtained The rocker is clamped in this position and very often dowelled to the end shield
39 End shiled
(1) The end shield is bolted to the frame and held true by spigot Ensiled
(2) It holds the armature bearings in position and also provides a base for the brush assembly
(3) Generally end shields contain suitable openings for servicing of brushes and have inlets and outlets for cooling air if required
310 Main Field Winging
The purpose of the magneto motive force produced by this winding is to establish the magnetic field through which the armature conductors move It is possible to construct a curve showing the relationship between field current and magnetic flux for a given magnetic circuit This is termed the magnetization curve and usually applies to a given specified speed
311 Inter pole Coil
This coil produces a magnetic field which helps the armature coil current to reverse or commutate It also helps to overcome the magnetic field produced by the armature and is connected in series with the armature The number of turns on this coil are related to the number of turns and type of connection used on the armature winding and to the number of compensating poles relative to main poles
312 Compensating Winding
This winding is generally only used on large highly rated machines Very simply it compensates for and cancels out the detrimental effect of the armature magnetic field on the main magnetic field The shoe portion of the main field pole lamination is made deeper and slots are punched in the pole face facing the armature to take the compensating winding
313 Armature Windings
The emf or the force produced by one conductor in a motor or generator is insufficient for practical purposes and as a result armatures in practical machines require many conductors to perform effectively The method of interconnection of these conductors and the connection to the commutator to enable the necessary transfer of electrical energy form to armature system to the external circuit to be effected are termed the armature winding The two types of windings are termed lap windings and wave wondings
新代旋转电机定子绕组改进绝缘系统
摘
年明显趋势：较高额定功率（空冷电机功率高达300MVA氢冷电机功率约450 MVA）电机采定子绕组绝缘系统提出新求设计电机时项文述改良合成树脂绝缘改进结构MicadurPlus改变绝缘结构中加入金属氧化物粉末导热系数提高1倍叙述产生提高绝缘系统短期长期性变化提高绝缘质量基础重新优化电机设计点根证实
关键词
汽轮发电机定子绕组绝缘系统导体间接冷导热系数
1：前言
十年里定子绕组导体间接冷汽轮发电机进行研究已功率提高目前针年前绕组导体直接水冷氢冷实现单机额定功率正制造采述间接冷技术电机
1970年投入输出功率130MAV空冷电机直运行着具更单机额定功率燃气轮机发展目前趋势300MAV功率空冷汽轮发电机汽轮发电机采氢冷允许更高单机额定功率50年代末导体间接冷电机功率已达250MAV目前达350MAV
较发电机导体直接冷相定子绕组间接冷优点：
：线棒制造简单费较少
二：直接冷时冷剂需占空间绕组铜线
三：需辅助设备（例水冷时需）
方面间接冷需通绕包定子绕组线棒绝缘导体产生热损失散逸出定子绕组热良体根面研究情况涉温降整温升20~40
导体间接冷电机选择佳冷技术外需断改进绝缘系统助课题发展60年代热塑性云母箔绝缘环氧树脂基合成树脂绝缘变革改进绝缘材料物理性特进步型发电机采整体浸渍热导体系数进步改善绕组热耗更散逸进步提高间接冷电机功率
2改进绝缘系统电机设计影响
21冷原理
碟片铁心涂绝缘漆电工硅钢片叠成径通风糟钢铁芯分成干段普通设计中铁心分成冷区域通固定定子机座中轴道引入冷空气
气体径流铁心通风槽吸收铁心产生铁损定子线棒产生铜损放出热量定子绕组总温升包括冷剂温升流热传导产生温降气体冷定子绕组表面前吸收热损已具定温度该温度吸收铁损铜损进步升高通绝缘热传导必须散逸绕组铜损散发掉风道区利冷空气直流流线棒表面产生流进行热传导带电部件部分绕组损耗首先传递定子齿然散逸流通风道气体中
22 空冷汽轮发电机实例
典型实例中流损耗约占总温升35理通冷气体速度减少部分损耗助定流速难改善热传导外获更高流速需非常风机压力风机性项措施减少损耗寄予较希
利热传导线棒产生热通绝缘发散掉首先铜铁心间温差似表示Tipdrs
式中p散逸耗损
d 绝缘厚度
r导热系数
s热传导面积
绝缘厚度取决电机额定电压便更改改进绝缘材料热导系数减少铜铁芯间温差保持温升变情况增加绕组散逸损耗做实例流占导位时铜铁心间温差降
外实例绕组中散逸约14热损耗铜损耗负载电流方增加线电流密度约增加7电机功率线电流密度成正电机功率样例增加
增加额定功率性取决参数提高电压增加绝缘厚度铜铁心间温差占总温升份额较改善定子绝缘热导系数空冷发电机额定功率提高510较高励磁安匝转子必须够承受定子产生较高反安匝
直流电机原理
1 概述
作电机中类直流电机包括发出直流电直流电电机种情况电机量转换装置转换机械电时装置发电机果转换方进行装置便做电动机发电机电动机基结构细节间存差异两种情况原理相面原理进行讨
2 发电机发电机作
发电机产生作基础样事实导体相磁场作切割力线（磁场）运行时导体中感应出emf （电动力）电动力取决导体磁场中运动速度
电动机述事实基础磁场处中载流导体施加机械力机械力磁场强度电流积成正发电机中感应出电动力场导体运动方间存着确定关系电动机中产生力导线中电流磁场间存着确定关系
发电机中种关系概括说右手定电动机中基规左手定
定条件电机作发电机运行做电动机运行程度取决电机状态参数取决电机供电系统间电流动方
3 发电机结构
面描述解释应发电机应电动机描述中具良电磁特性材料指够高铜密度工作会产生饱磁滞损耗低材料括号中部件常名
31 机座
制造电机基础结构具述作特点：（1）包括磁极气隙电枢磁场形成完整磁路磁场磁通提供返回通路（2）现代实物中机座具良电磁钢板铸铁制成时磁滞损耗低重假设磁通恒定（3）机座刚性支架磁极端盖螺栓拧合支脚焊边机座铸造成时整体机座组成部分
32 级系统
（1）板10—15毫米优质电磁钢片叠装成铆合起长度电枢铁芯样（2）磁板提供水支座支撑励磁绕组极身缩短保持磁场线圈匝均长度短减少线圈电阻损耗（3）通常情况定输出范围采磁极数目定磁极数目偶数输出越高磁极数目越
33 换阀
（1）换极安装极间圆弧部分通常换极数目级数目相等情况致隔格磁极安装励磁绕组（2）换极形状矩形实心结构积累似层压结构（3）采行钢棒结构时换极线圈夹子类似装置固定
34 电枢铁芯
（1）电枢铁芯层压钢板制成具非常电磁特性铁损低电枢绕组需载通交流电点外层钢片进行绝缘进步减少涡流损耗（2）铁芯周角开槽承接线圈电枢线圈安装槽中（3）铁芯两块端板紧紧夹住键装配轴型电机磁极铁心通风结构冷气体通
35 换器
换器片（扇形片）硬拉镀银钢材制成V形钢槽固定V形钢槽铸钢加工成换片支撑V形间进行绝缘绝缘V形云母制成换片间绝缘云母进行连接换片升角开槽焊接电枢导线焊里面
36 电刷
电刷作电枢搜集电流电枢提供电流根电机途种专碳材料制造电刷理想碳材料寿命长换器磨损忽略具良换性
37 刷架
刷架电刷固定定位置换器相接触滑动侧移动电刷正确压力换器相接触采系列弹簧电刷牢固压换器
38 刷握
刷握两部分组成刷握环刷握杆刷握杆夹刷握环定位置刷握环相绝缘刷握通常固定端盖鸽尾槽中电刷绕换器转动直位置刷握夹定位置常常铰接端盖
39 端盖
（1）端盖螺栓合机座套加固（2）支撑电枢轴承题供安装基础（3）端盖通常带适开口维护电刷果需冷气体进出通道
310 磁场绕组
绕组产生磁动力作建立磁场没电枢导线中运动建立定雌路磁场电流磁通间关系曲线条曲线做磁化曲线常定速
311 换极线圈
线圈产生磁场磁场帮助电枢线圈电流反换帮助克服电枢产生磁场换极线圈电枢串联连接线圈匝数电枢绕组匝数连接方式关补偿极数极极数关
312 补偿绕组
种绕组型高功率电机非常简单补偿消电枢磁极磁场磁场害影响磁极层压铁芯极靴部分做较深磁极表面电枢面槽容纳补偿绕组
313 电枢绕组
电动机发电机中根导体产生emf电动力足
进行实际应实际电机中需许许根导线效运行完成电电枢系统外电路传送必须导线相互连接起连接换器连接线圈做电枢绕组两种形式电枢绕组种做绕组种做叠绕组
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Summary
In recent years there has been a distinct trend to utilize machines with indirectly cooled stator windings also for the higher ratings up to about 300 MVA with air cooling and about 450 MVA with hydrogen cooling This imposed new demands on the wellknown dielectric requirements as this is a key item when laying out the machine
This report describes the modified structure of an improved synthetic resin insulation MatadorPlus The most significant change was the introduction of powdered metaloxyde to the insulation structure used hitherto which it enable the thermals conductivity to be doubled The resulting characteristically changes are described relative to both short and long term behaviors of the insulation system
Based on the improved insulating qualities it was possible to reoptimize machine designs which is fundamentally demonstrated
Key words
Turbogenerator stator winding insulation system indirect conductor cooling thermal conductivity
1Introduction
Over the last decades the development of turbogenerators with indirect conductor cooling in the stator winding has led to ever increasing ratings Today machines are being built with this technology for ratings which just a few years ago were only possible with direct water or hydrogen cooling of the stator winding conductors
Air—cooled machines with ratings of up to 130 MVA were already in service by 1970With the development of gas turbines with larger unit ratings there is a trend today for aircooled turbogenerators with ratings of 300 MVA Hydrogen cooling in turbo generators permitted much higher unit ratings By the of the 50’s machines with indirect conductor cooling had been realized up to 250 MVA and today the limit is above 350 MVA
Compared with direct conductor cooling used on larger generators indirect cooling of the stator ending has the advantages that bar production is simple and less expensive the space needed for coolant flow with direct cooling is available for instance with water cooling
On the other hand indirect cooling requires that the heat losses generated in the conductors ate dissipated via the insulation wrapping on the stator winding bars which is a poor thermal conductor Depending on the case under consideration the temperature drop involved represent 20…40 of the total temperature rise
Besides the need to optimize the cooling technique on machines with indirect conductor cooling there was also the continuous requirement to improve the insulation system which helped to make this course in development possible The change in the 60’s from thermoplastic micafolium insulation system which helped to make thermoplastic micafolium insulations to epo
xy resin bases\d synthetic resin insulation led to considerable improvement in the physical and particularly in the dielectric properties of the insulation material A further step in the 70’s saw the introduction of total immersion impregnation also for large generator[45] The now further improved thermal conductivity allows a better dissipation of the winding heat losses and so a further increase in the ratings for indirect cooled machines
2Effect of the improved insulation system on machine design
21 Cooling principle
The laminated core is built up from varnish insulated electrical sheet segments and is subdivided into packets by radial duct spacers which form passages for the cooling gas flow In one of the most common designs the core is split up into different cooling zones whereby the cooling gas is led in through axial tubes located in the stator housing
The gas flows radically through the core ducts and absorbs the iron losses produced in the core and the copper losses generated in the stator bars The total temperature drop due to convection and thermal conduction The gas absorbs other heat losses before reaching the cooling surfaces of the stator winding and therefore already has a certain temperature which increases further after absorbing the iron and copper losses The winding copper losses must be dissipated by thermal conduction via the insulation In the regions of the cooling ducts heat transfer is by convection directly to the cooling gas flowing over the bar surfaces The larger portion of the winding losses in the active part is first transferred to the stator teeth and then dissipated to the gas flowing through the cooling ducts
22 Example of an aircooled turbogenerator
In a typical example dissipation by convection represents approximately 35 of the total temperature rise This portion could theoretically be reduced by increasing the velocity of the cooling gas However from a certain flow velocity heat transfer can hardly be improved upon and moreover in order to achieve higher flow velocity of the cooling gas However from a certain flow velocity heat transfer can hardly be improved upon and moreover in order to achieve higher flow velocities excessive fan pressures and consequently fan performances are necessary therefore this possibility does not offer much chance of reduction
The heat from the bar must be dissipated through the insulation by thermal conduction For a first approximation the temperature difference between the copper and the core can be taken as being
TiPdrs
Where PLosses to be dissipated
DInsulation thickness
SHear transfer area
RThermal conductivity
The insulation thickness is dependent on the rated voltage of the machine and therefore can nit be changed at all will Nevertheless the temperature difference between the copper and the core can be decreased thanks to an improved thermal conductivity of the insulation material It is therefore possible to increase the losses to be dissipated from the winding while maintaining the total temperature rise As an example the temperature difference between copper and core decreases while the convection part between copper and core decreases while the convection part becomes more dominant
The possible increase in rating depends on various parameters Increase voltage results in increased insulation thickness and therefore the temperature difference copper to core has a greater part of the total temperature rise The improved thermal conductivity of the stator insulation permits a possible increased rating for air—cooled generators in the r\range of 5…10 The rotor must be able to cover the higher back ampereturns produced by the stator by higher field ampere turns
D．C．MACHINE PRINCIPLES
1 Introduction
Direct current machines as a class include those machines that either produce or utilize direct current In either case the machine function as an energy conversion is from mechanical to electrical energy the machine is termed a generator If the conversion process proceeds in the other direction the machine is a motor There is no different principles involved in each case There principles are now discussed
2 Generator and Motor Action
Generator action is based upon the fact an emf (electromotive force) is induced in a conductor when the conductor moves in such a direction relative to a magnetic field that the conductor cuts the rate at which the conductor is moving relative to the magnetic field
Motor action is based upon the fact that a mechanical force is exerted on a currentcarrying conductor in a magnetic field The magnitude of the force is proportional to the product of the field strength and the current
There are definite relationships between the direction of the induced emf field and conductor motion in the case of a generator and the direction of the developed force conductor current and field in the case of a motor
For a generator the relationship is summarized in what is termed Flemings Right Hand Rule
Where a motor is being considered the basic rule is Flemings left Hand Rule
Where a machine operates as a motor or a generator in a given situation is largely independent of the machine conditions and parameters but depends on the direction of power flow between the machine and the electrical supply system
3 Generator Construction
The following descriptions and explanations apply to both motors and generators In the descriptions a material having good magnetic characteristics is one that can be worked at high values of flux density without saturation occurring and with a low hysteresis loss Where an alternative name for a component is common it is given in brackets
31 (Frame B Yoke ody)
This is the base on which the machine is built It has the following functions and characteristics
(1) The yoke completes the magnetic circuit comprising the poles air gaps and armature and gives a return path for the field flux
(2) Modern practice is to make the yoke of steel plate or cast steel of a good magnetic characteristic In this instance a low hysteresis loss is not important as the flux can be assumed to be constant
(3) The yoke also acts as a rigid frame to which piles and end shields are bolted and to which holding down feet are welded These are all an integral part of the yoke when the yoke is cast
32 Main pole System
(1) Each main pole is an assembly of steel laminations of good magnetic characteristics between 10 and 15 mm thick riveted together and of the same length as armature core
(2) Each pole provides a level seat for supporting a main field excitation coil The body of the pole is reduced to keep the mean length of turn of a main field coil to a minimum thereby reducing the coil resistance and losses
(3) Generally a given number of poles covers a given output range It will be appreciated that the number of poles will be an even number In general the larger the out put the greater the number of losses
33 Inter poles (Commutating Poles)
(1) Inter poles are fitted in the inter polar arc between the main poles and there are generally the same number of inter poles as main plows In some cases however only every alternate pole carries an excitation winding
(2) The poles can be either rectangular in shape and solid construction or alternatively they can be of laminated construction similar to the main pole
(3) Where steel bar parallel construction is used the inter pole coil held in position by clips or a similar device
34 Armature Core
(1) This is made up of iron laminations with very good magnetic characteristics and low iron loss since as will be seen later the armature winding carries an alternating current In addition each lamination is insulated to reduce eddy current losses further
(2) Slots are notched on the periphery of the core to take the coilsthe armature coils are fitted into these slots
(3) The cote is clamped firmly between two endplates and is keys to the shaft and on large machines pole vents are provided in the core to allow cooling air to pass through
35 Commutator
The commutator bars (or segments) are made of hard drawn or silvered copper held in place by steel vees which are rather of cast steel or machined from a bar The segments are insulate from the holding vees Insulation vees are made of mica In order to make the connections each bar is dotters in the riser portion and armature conductors ate then soldered in
Commutators must be machined to a very high degree of accuracy to ensure a smooth true surface for brushes to run on at all speeds
36 Brushes
The function of the brushes is to collect current from or supply current to armatures Depending on the purpose of the machine the brushes are made of special types of carbon Ideal carbon has long life negligible wearing effect on commutators and good commutating properties
37 Brushes Holder (Brush box)
The brush holder holds the brushes is the brush in position in contact with the commutator allowing it to slide up and down but without allowing side movement In order to maintain the correct pressure aspiring arrangement presses the brush firmly on to the commutator
The brush holder is clamped to the rocker arm
38 Brush Rocker
The brush rocker consists of two parts a rocker ring and a rocker arm The rocker arm is clamped into position on to the rocker ring and is insulated from it The bruch rocker generally fits on a spigot inside the end shield enabling the brushes to be rotated round the commutator until the best brush position is obtained The rocker is clamped in this position and very often dowelled to the end shield
39 End shiled
(1) The end shield is bolted to the frame and held true by spigot Ensiled
(2) It holds the armature bearings in position and also provides a base for the brush assembly
(3) Generally end shields contain suitable openings for servicing of brushes and have inlets and outlets for cooling air if required
310 Main Field Winging
The purpose of the magneto motive force produced by this winding is to establish the magnetic field through which the armature conductors move It is possible to construct a curve showing the relationship between field current and magnetic flux for a given magnetic circuit This is termed the magnetization curve and usually applies to a given specified speed
311 Inter pole Coil
This coil produces a magnetic field which helps the armature coil current to reverse or commutate It also helps to overcome the magnetic field produced by the armature and is connected in series with the armature The number of turns on this coil are related to the number of turns and type of connection used on the armature winding and to the number of compensating poles relative to main poles
312 Compensating Winding
This winding is generally only used on large highly rated machines Very simply it compensates for and cancels out the detrimental effect of the armature magnetic field on the main magnetic field The shoe portion of the main field pole lamination is made deeper and slots are punched in the pole face facing the armature to take the compensating winding
313 Armature Windings
The emf or the force produced by one conductor in a motor or generator is insufficient for practical purposes and as a result armatures in practical machines require many conductors to perform effectively The method of interconnection of these conductors and the connection to the commutator to enable the necessary transfer of electrical energy form to armature system to the external circuit to be effected are termed the armature winding The two types of windings are termed lap windings and wave wondings
新代旋转电机定子绕组改进绝缘系统
摘
年明显趋势：较高额定功率（空冷电机功率高达300MVA氢冷电机功率约450 MVA）电机采定子绕组绝缘系统提出新求设计电机时项文述改良合成树脂绝缘改进结构MicadurPlus改变绝缘结构中加入金属氧化物粉末导热系数提高1倍叙述产生提高绝缘系统短期长期性变化提高绝缘质量基础重新优化电机设计点根证实
关键词
汽轮发电机定子绕组绝缘系统导体间接冷导热系数
1：前言
十年里定子绕组导体间接冷汽轮发电机进行研究已功率提高目前针年前绕组导体直接水冷氢冷实现单机额定功率正制造采述间接冷技术电机
1970年投入输出功率130MAV空冷电机直运行着具更单机额定功率燃气轮机发展目前趋势300MAV功率空冷汽轮发电机汽轮发电机采氢冷允许更高单机额定功率50年代末导体间接冷电机功率已达250MAV目前达350MAV
较发电机导体直接冷相定子绕组间接冷优点：
：线棒制造简单费较少
二：直接冷时冷剂需占空间绕组铜线
三：需辅助设备（例水冷时需）
方面间接冷需通绕包定子绕组线棒绝缘导体产生热损失散逸出定子绕组热良体根面研究情况涉温降整温升20~40
导体间接冷电机选择佳冷技术外需断改进绝缘系统助课题发展60年代热塑性云母箔绝缘环氧树脂基合成树脂绝缘变革改进绝缘材料物理性特进步型发电机采整体浸渍热导体系数进步改善绕组热耗更散逸进步提高间接冷电机功率
2改进绝缘系统电机设计影响
21冷原理
碟片铁心涂绝缘漆电工硅钢片叠成径通风糟钢铁芯分成干段普通设计中铁心分成冷区域通固定定子机座中轴道引入冷空气
气体径流铁心通风槽吸收铁心产生铁损定子线棒产生铜损放出热量定子绕组总温升包括冷剂温升流热传导产生温降气体冷定子绕组表面前吸收热损已具定温度该温度吸收铁损铜损进步升高通绝缘热传导必须散逸绕组铜损散发掉风道区利冷空气直流流线棒表面产生流进行热传导带电部件部分绕组损耗首先传递定子齿然散逸流通风道气体中
22 空冷汽轮发电机实例
典型实例中流损耗约占总温升35理通冷气体速度减少部分损耗助定流速难改善热传导外获更高流速需非常风机压力风机性项措施减少损耗寄予较希
利热传导线棒产生热通绝缘发散掉首先铜铁心间温差似表示Tipdrs
式中p散逸耗损
d 绝缘厚度
r导热系数
s热传导面积
绝缘厚度取决电机额定电压便更改改进绝缘材料热导系数减少铜铁芯间温差保持温升变情况增加绕组散逸损耗做实例流占导位时铜铁心间温差降
外实例绕组中散逸约14热损耗铜损耗负载电流方增加线电流密度约增加7电机功率线电流密度成正电机功率样例增加
增加额定功率性取决参数提高电压增加绝缘厚度铜铁心间温差占总温升份额较改善定子绝缘热导系数空冷发电机额定功率提高510较高励磁安匝转子必须够承受定子产生较高反安匝
直流电机原理
1 概述
作电机中类直流电机包括发出直流电直流电电机种情况电机量转换装置转换机械电时装置发电机果转换方进行装置便做电动机发电机电动机基结构细节间存差异两种情况原理相面原理进行讨
2 发电机发电机作
发电机产生作基础样事实导体相磁场作切割力线（磁场）运行时导体中感应出emf （电动力）电动力取决导体磁场中运动速度
电动机述事实基础磁场处中载流导体施加机械力机械力磁场强度电流积成正发电机中感应出电动力场导体运动方间存着确定关系电动机中产生力导线中电流磁场间存着确定关系
发电机中种关系概括说右手定电动机中基规左手定
定条件电机作发电机运行做电动机运行程度取决电机状态参数取决电机供电系统间电流动方
3 发电机结构
面描述解释应发电机应电动机描述中具良电磁特性材料指够高铜密度工作会产生饱磁滞损耗低材料括号中部件常名
31 机座
制造电机基础结构具述作特点：（1）包括磁极气隙电枢磁场形成完整磁路磁场磁通提供返回通路（2）现代实物中机座具良电磁钢板铸铁制成时磁滞损耗低重假设磁通恒定（3）机座刚性支架磁极端盖螺栓拧合支脚焊边机座铸造成时整体机座组成部分
32 级系统
（1）板10—15毫米优质电磁钢片叠装成铆合起长度电枢铁芯样（2）磁板提供水支座支撑励磁绕组极身缩短保持磁场线圈匝均长度短减少线圈电阻损耗（3）通常情况定输出范围采磁极数目定磁极数目偶数输出越高磁极数目越
33 换阀
（1）换极安装极间圆弧部分通常换极数目级数目相等情况致隔格磁极安装励磁绕组（2）换极形状矩形实心结构积累似层压结构（3）采行钢棒结构时换极线圈夹子类似装置固定
34 电枢铁芯
（1）电枢铁芯层压钢板制成具非常电磁特性铁损低电枢绕组需载通交流电点外层钢片进行绝缘进步减少涡流损耗（2）铁芯周角开槽承接线圈电枢线圈安装槽中（3）铁芯两块端板紧紧夹住键装配轴型电机磁极铁心通风结构冷气体通
35 换器
换器片（扇形片）硬拉镀银钢材制成V形钢槽固定V形钢槽铸钢加工成换片支撑V形间进行绝缘绝缘V形云母制成换片间绝缘云母进行连接换片升角开槽焊接电枢导线焊里面
36 电刷
电刷作电枢搜集电流电枢提供电流根电机途种专碳材料制造电刷理想碳材料寿命长换器磨损忽略具良换性
37 刷架
刷架电刷固定定位置换器相接触滑动侧移动电刷正确压力换器相接触采系列弹簧电刷牢固压换器
38 刷握
刷握两部分组成刷握环刷握杆刷握杆夹刷握环定位置刷握环相绝缘刷握通常固定端盖鸽尾槽中电刷绕换器转动直位置刷握夹定位置常常铰接端盖
39 端盖
（1）端盖螺栓合机座套加固（2）支撑电枢轴承题供安装基础（3）端盖通常带适开口维护电刷果需冷气体进出通道
310 磁场绕组
绕组产生磁动力作建立磁场没电枢导线中运动建立定雌路磁场电流磁通间关系曲线条曲线做磁化曲线常定速
311 换极线圈
线圈产生磁场磁场帮助电枢线圈电流反换帮助克服电枢产生磁场换极线圈电枢串联连接线圈匝数电枢绕组匝数连接方式关补偿极数极极数关
312 补偿绕组
种绕组型高功率电机非常简单补偿消电枢磁极磁场磁场害影响磁极层压铁芯极靴部分做较深磁极表面电枢面槽容纳补偿绕组
313 电枢绕组
电动机发电机中根导体产生emf电动力足
进行实际应实际电机中需许许根导线效运行完成电电枢系统外电路传送必须导线相互连接起连接换器连接线圈做电枢绕组两种形式电枢绕组种做绕组种做叠绕组
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