performance. On the other hand, higher draft tube call for more concrete, thereby building up the cost of the power house. For this reason, an optimum must be found that would be economical of materials and still ensure an acceptable performance, as too low draft tubes have proved to be very little help.
至于尾水管的形状，直锥形尾水管可能获得最佳性能。不幸的是，由于其喉部直径，它的长度将较大，而且因此，对于大型机械，它可能会需要非常可观的开挖量。因此，它仅用相对较小的机械，对于大型垂直轴水轮机的尾水管，通常是弯肘建筑物。事实上，弯肘型尾水管目前最普遍地应用于水轮机安装中。对于这种类型，垂直段通常开始于直锥段，它在肘管段逐渐趋于复杂形状，随后水流通过大致呈矩形的扩散段水平地流向尾水。考虑结构因素，在尾水管的水平部分设置了一个或两个垂直支墩。任何尾水管的基本尺寸都是高度h。很明显，尾水管越高，其性能越好。另一方面，较高的尾水管需要更多的混凝土，由此增加了厂房的成本。基于此，必须在材料经济性和确保能接受的性能之间作出最佳选择，因为太低的尾水管已经被证明没有太多用处。
Empirical relations and experience curves have been developed to make preliminary determinations for Francis turbines draft tube design. The turbine discharge diameter, D3 and specific speed, ns are used as reference parameters for developing the appropriate controlling dimensions according to de Siervo and de Leva(1976). The absolute velocity at the inlet to the draft tube is given by the following equation:
248
??3=8.74+ ????where ??3=water velocity at the draft tube inlet section, m/sec; ????=turbine specific speed.
对于弗朗西斯水轮机尾水管的设计，已经获得了初步确定的试验关系和经验去西安。根据西尔沃和德勒瓦，将水轮机泄流直径D3和比转速ns作为确定合适的控制尺寸的参考参数。尾水管进口处的绝对速度用下式表示：
248
??3=8.74+ ????其中??3=尾水管进口处的水流速度，米/秒； ????=水轮机比转速。
As the specific speed increases, there is a tendency for controlling dimensions to be increased because the amount of kinetic energy within the draft tube relative to the potential energy is larger, but countering that is the higher cost for the civil works to accommodate the larger dimensions. The experience curves tend to indicate that the civil works cost limitations control the relative size at higher values of specific speed.
当比转速增加，控制尺寸有增加的趋势，因为在尾水管内的动能相对于势能变大，但是容纳较大尺寸的土建工程的成本反而更高。经验公式趋于表明，土建工程成本的限制控制着更高比转速度值处的相对尺寸。
12. Synchronous Generators 12. 同步发电机
Converting water energy to electric energy at hydropower plants is possible through the
operation and functioning of electrical generators. The phenomenon of producing an electrical current in a conductor, discovered by Michael Faraday, involves moving a copper coil through a stationary magnetic field or moving a magnet through a copper coil. In the practical generator, an induced voltage is caused by the magnetic field of a rotor sweeping by the coils of the stator. The rotor of an electrical generator in the case of hydropower developments is driven by the rotation of the turbine. Usually, the turbine and generator are directly connected on a common shaft. Most generators used in hydropower developments are alternating current (AC) synchronous generators. These require excitation current which is usually provided by a small auxiliary generator that supplies direct current to create the magnetic field of the rotor.
在水电厂房中，通过发电机的操作和功能可以将水能转换成电能。由米歇尔·法拉第发现的在一个导体产生电流的现象，包括在恒定磁场中移动铜绕组或在铜绕组中移动一个磁铁。在实际的发电机中，由转子上的磁场切割定子上的绕组就产生了一个感应电势。在水电开发中，发电机的转子是由水轮机的转动而驱动的。通常，水轮机和发电机直接在一个普通的轴上直接连接。在水电开发中应用的大多数发电机是交流同步发电机。这些要求通常是由一个小的辅助发电机供给直流电流来创建所述转子的磁场提供励磁电流。
The basic components of generators as used with hydraulic turbines are (1) supporting frame, (2) shaft that transmits the rotating motion of the turbine, (3) exciter, (4) assembly of the built-up rotor, (5) rotor poles, (6)stator and its component coils, (7) stator coil supports, (8) air cooler, (9) thrust bearings for vertical shaft machines, and (10) brake.
用在水轮机上的发电机的基本组成部分是（1）支持框架，（2）传递水轮机转动运动的轴，（3）励磁器，（4）装配式转子支架，（5）转子磁极，（6）定子及其组件绕组，（7）定子绕组支架，（8）空气冷却器，（9）对垂直轴机械的推力轴承，以及（10）闸。
The stator contains the armature in conventional ac generators and consists of windings of coils pressed into slots in a symmetrical pattern. The core of stator is composed of laminated steel sheets to reduce power losses by eddy currents.
常规发电机的定子包括有铁芯和一些列以对称布置方式压进铁芯槽中的绕组。定子的核心由压层钢板组成以减少由涡流造成的电力损失。
The rotor contains the coils that make up the electromagnets or field winding. The windings surround the individual poles that are mounted on structure that makes up a wheel attached to the rotary shaft. If the windings surround each pole in a symmetrical fashion and are wound individually around a pole that extends out from a cylindrical surface, they are termed salient-pole fields.
转子包括组成电磁体或磁场绕组的线圈。绕组围绕在安装于组成附着于转轴的轮毂的结构上。如果绕组对称地围绕着每个磁极，且分别缠绕于从圆柱体表面延伸出来的磁极上，那么它们被称为凸极磁场。
The number of coils, the wire size and number of turns in a coil, and the number of slots in a stator are design considerations by which size and capacity of the generator are varied. These windings may be connected in series or parallel to achieve the desired voltage or current ratings. For actual functioning of the generator, it is then necessary to have twice the number of coils per phase per pair of poles.
线圈的数量、线径和线圈中的匝数，以及定子中的插槽数的设计考虑是根据发电机变化尺寸和容量而定。这些绕组可以是成串联或并联，以获得所需的额定电压或电流。对于发电机的实际功能，每对磁极的每相的绕组数都必须翻倍。
The field winding magnetic circuit and rotor consists of poles that are duplicates of each
other that they are arranged alternately north and south magnetically. A full cycle of alternating current is developed for each pair of magnetic poles swept by the winding, that is, one cycle per two poles. The fixed number of poles is provided in a full circle and must be an even-integer number of poles, because a north pole must exist for each south pole. The following fundamental formula must be met:
??????
120where f=frequency, Hz(=cycles/sec); ????=number of poles; n=speed, rpm.
??=
该励磁绕组磁路和转子由可互相代替的磁极组成，交替排列在南北磁性。每对磁极切割绕组产生的完整周期的交流电，即，每两个磁极一个循环。一个完整周期中提供固定数目的磁极，且该磁极数目必须为偶数，因为每个北极必须对应一个南极。必须满足以下基础公式：
??????
120其中f=频率，赫兹（=圈/秒）；????=磁极数；n=速度，转每分钟。
There are only a limited number of frequencies used for ac power frequencies. The usual ones are 25, 50, 60, and 400Hz. The most common frequency used with hydropower generators in North America is 60 Hz.
对于交流电流仅应用有限的频率。通常的频率是25、50、60和400赫兹。在北美水力发电机所应用的最普遍的频率是60赫兹。
??=
13. Speed Control and Governors（1） 13. 调速与调速器（1）
Much equipment connected to a hydroelectric system is sensitive to frequency variation. Therefore, speed control of the system is a necessity. Regulating the quantity of water admitted to the turbine runner is the usual means of regulating and maintaining a constant speed to drive the generator and to regulate the power output. This is done by operating wicket gates or valves. Such action requires a mechanism to control the wicket gates, which is the governor or governor system. At decreasing load, the speed tends to rise, and the governor has to close the wicket gates to such an extent that the torque created by the turbine equals the torque offered by the electrical load on the generator and the speed returns to the desired synchronous speed. As the wicket gates open, the speed adjustment is lowered and the inherent tendency of the turbine unit is to pick up additional load in response to a decrease in system speed.
很多与水电系统相连的设备都对频率变化很敏感。因此，系统的调速是必需的。调节进入水轮机转轮的水量是调节和维持一个恒定速度以驱动发电机和调节电力输出的通常手段。这是通过操控导水叶或阀门而完成的。这个操作需要一个控制导水叶的机制，也就是调速器和调速器系统。在减少负荷时，速度趋于增加，且调速器不得不调整导水叶使得水轮机产生的扭矩与调速器上电力负荷提供的扭矩相同，并且其速度发过来达到所期望的同步速度。随着导水叶的开启，速度调节器随之降低且水轮机机组的固有趋势是拾起额外负荷以应对系统速度的降低。
The function of the governor is to detect any error in speed between actual and desired values and to effect a change in the turbine output. This is done so that the system load is in equilibrium with the generating unit output at the desired speed.
调速器的功能是检测实际速度与期望值之间的任何错误，且影响水轮机输出的变化。这样做是为了使得系统负荷与机组输出在期望的速度下相平衡。
The governor system of the turbine acts as an opening, closing, and gate-setting mechanism for starting, stopping, and synchronizing the turbine which allows for matching output to the system load to maintain the system frequency and creates the necessary adjustment on Kaplan turbine blade angles for optimum operation at synchronous speed.
水轮机调速系统的作用类似于一个开启、关闭和定位阀门的装置，使水轮机能够开机、关机和保持同步转速运行，维持水轮机负荷与系统负荷之间平衡，确保系统频率稳定。同时，该系统还能调节卡普兰水轮机的叶片转角，从而保证水轮机以同步转速在最优工况下运行。
Governor systems can be classified as either mechanical-hydraulic governors or electro-hydraulic governors. The three elements of operation are (1) the speed-responsive system for detecting changes in speed, (2) the power component for operating the wicket gates, and (3) the stabilizing or compensating element that prevents runaway speed in the turbine and holds the servomotor in fixed position when the turbine output and the generator load are equalized. The servomotor is the oil pressure system and piston arrangement used to operate the wicket gates.
调速器系统可以被划分为机械液压式调速器或电气液压式调速器。操作的三个要素是：（1）检测速度变化的速度响应系统；（2）操作导水叶的电力组件；（3）稳定或补偿元件，当水轮机输出趋于与发电机负荷相等时，防止水轮机中的飞逸转速并在固定位置稳住住接力器。接力器是用于操作导水叶的油压系统和活塞装置。
A mechanical-hydraulic governor is a unit in which a mechanical centrifugal pendulum acts as a sensor. The flyballs of the pendulum move outward with increasing speed and inward with decreasing speed. The movement of the flyballs is transferred by means of a rod and links to the pilot valve of the governor, which in turn operates the servomechanism for changing the position of the wicket gates. In a Kaplan turbine, the propeller blades are controlled by a separate servomotor with a series of cams or a microprocessor to maintain a position relative to the head and gate position. The flyball mechanism does not have power output necessary to move the wicket gates on a hydraulic turbine. The power for moving the wicket gates is normally supplied by a hydraulic system controlled by the flyball action.
机械液压式调速器是一个机械离心飞摆作为传感器的单元。离心飞摆在向外运动时速度增加，在向内运动时速度降低。离心飞摆的运动通过杆的装置传送，且与调速器的引导阀相连。这反过来操作伺服机构以改变导水叶的位置。在卡普兰水轮机中，螺旋桨式叶片收到一个独立的伺服机构控制，其中一系列的凸轮或微处理器维持在相对于水头和闸门位置的位置。离心飞摆机制没有移动水轮机导叶的必需的电力输出。移动导水叶的电力通常由离心飞摆运动控制的液压系统提供。
14. Speed Control and Governors（2） 14. 调速与调速器（2）
The power component of the entire governor system and gate operating system consists of (1) the servomotor, a fluid-pressure-operated piston or pistons to move the wicket gates; (2) the oil pressure supply, which furnishes the power for the action of the servomotor; and (3) a control valve, which regulates oil pressure and flow of oil in the servomotor.
整个调速器系统和闸门操作系统的电力元件包括（1）伺服电动机，一个移动导水叶的流体压力操作的活塞或活塞；（2）油压供给，它为伺服电动机的运动提供电力；和（3）控制阀，它调整伺服电动机中的油压和油的流动。
The sequence of governor operation consists of the action of flyballs, which respond to the speed change and transmit motion through the system of floating levers to the pilot valve. The pilot valve equipped with relay valves causes oil pressure to be transmitted to one side or the other of the servomotor. The action of the piston of the servomotor in turn opens or closes the turbine wicket gates and regulates the flow of water to change the speed.
调速器操作序列包括离心飞摆的运动，它通过浮筒杆系统向先导阀响应速度变化和传递动作。配备配压阀的先导阀引起油压传递到伺服电动机的一边或另一边。伺服电动机活塞的运动反过来开启或关闭水轮机导叶并调节水流以改变速度。
The speed of a turbine will deviate from normal synchronous speed for a certain percentage of load change. The amount of deviation of speed will depend on (1) the time required to alter the flow of the hydraulic oil in the governor system to correspond with action necessitated by the change in load, (2) the amount of flywheel effect of the entire rotating mass of the turbine and generator, and (3) the time required for the water flow to respond to action caused by the change in the turbine operating point.
水轮机的速度会由于一定百分比的负荷变化而偏离正常的同步速度。速度偏离量取决于（1）改变调速器系统中的液压油以响应负荷变化所必需的动作所需的时间，（2）整个水轮机和调速器旋转系统的飞轮影响的数量，以及（3）水流响应由水轮机工况点变化引起的动作所需的时间。
The simple governor and control system is an isochronous governor. The isochronous governor is inherently unstable, and although some stabilization results from the characteristics of the turbine and connected load, these are generally inadequate and an additional means of stabilization effect of the inertia of the water flow in the penstock. The necessary stability is provided by feedback from the servomotor, which, by means of the dashpot, temporarily restores the control valve toward the null position, and dampens the servomotor movements. The dashpot functions with a spring-loaded valve that is mechanically linked to the servomotor and controls from the pilot valve and the flyball mechanism.
简单的调速器和控制系统是一个同步的调速器。该同步调速器本质上并不稳定，且尽管水轮机特性和连接负载之间稳定的结果，这些通常是在压力钢管中水流惯性的稳定影响的不充足和附加方法。伺服电动机提供了稳定性必需的反馈，而这通过缓冲器方法，暂时恢复向空白位置的控制阀，并抑制了伺服电动机的运动。缓冲器的运行要有一个弹簧式阀门，它机械地连接到伺服电动机并控制先导阀和离心飞摆机制。
To control the turbine speed, the governor must sense the system speed and compare it to a standard. In the case of a mechanical governor, the flyball mechanism is driven by a permanent magnet generator (PMG) attached to the generator shaft, or by a potential transformer (PT) so that any change in system speed results in a change in the flywheel mechanism’s position. In an electronic governor, the frequency may be sensed directly from a potential transformer or the output frequency of a speed signal generator (SSG) attached to the generator. The output