自动化专业英语 - 原文和翻译 - P1U5-

1、A Types of DC Motors直流电机分类The types of commercially available DC motors basically fall into four categories: permanent-magnet DC motors, series-wound DC motors, shunt-wound DC motors, and compound-wound DC motors. Each of these motors has different characteristics due to its basic circuit arrangemen

2、t and physical properties.1现在可以买到的直流电机基本上有四种:永磁直流电机,串励直流电机,并励直流电机,复励直流电机。每种类型的电动机由于其基本电路和物理特性的不同而具有不同的机械特性。Permanent-magnet DC Motors永磁直流电机The permanent-magnet DC motors, shown in Fig. 1-5A-1, is constructed in the same manner as its DC generator counterpart. The permanent-magnet DC motor is used fo

3、r low-torque applications.When this type of motor is used, the DC power supply is connected directly to the armature conductors through the brush/commutator assembly. The magnetic field is produced by permanent magnets mounted on the stator. The rotor of permanent magnet motors is a wound armature.永

4、磁直流电机,如图Fig. 1-5A-1所示,是用与直流发电机同样的方法建造的。永磁直流电机用于地转矩场和。当使用这种电机时,直流电源与电枢导体通过电刷/换向器装置直接连接。磁场由安装在定子上的永磁磁铁产生。永磁磁铁电机的转子是绕线式电枢。This type of motor ordinarily uses either alnico or ceramic permanent magnets rather than field coils. The alnico magnets are used with high-horsepower applications. Ceramic magnets

5、 are ordinarily used for low-horsepower slow-speed motors. Ceramic magnets are highly resistant to demagnetization, yet they are relatively low in magnetic-flux level. The magnets are usually mounted in the motor frame and then magnetized prior to the insertion of the armature.这种电机通常使用铝镍钴永磁合金或陶瓷永磁磁铁

6、而不是励磁线圈。铝镍钴永磁合金用于大功率电机。陶瓷永磁磁铁通常用于小功率、低速电机。陶瓷永磁磁铁抗退磁性能高,但它产生的磁通量较低。磁铁通常安装在电机外壳里边,在安装电枢前将其磁化。The permanent-magnet motor has several advantages over conventional types ofDC motors. One advantage is reduced operational cost. The speed characteristics of the permanent-magnet motor are similar to those of

7、 the shunt-wound DC motor. The direction of rotation of a permanent-magnet motor can be reversed by reversing the two power lines.永磁电机相对于常规直流电机有几个优点。优点之一是减少了运行损耗。永磁电机的转速特性类似于并励式直流电机的转速特性。永磁电机的旋转方向可通过将电源线反接来实现。Series-wound DC Motor串励式直流电动机The manner in which the armature and field circuits of a DC mo

8、tors are connected determines its basic characteristics. Each of the types of DC motors are similar in construction to the type of DC generator that corresponds to it.The only difference, in most cases, is that the generator acts as a voltage source while the motor functions as a mechanical power co

9、nversion device.2直流电机电枢和激磁电路的连接方式确定了直流电机的基本特性。每一种直流电机的结构与与其对应的直流发电机的结构类似。大部分情况下,二者的唯一区别在于发电机常作为电压源,而电动机常作为机械能转换装置。The series-wound motor, shown in Fig. 1-5A-2, has the armature and field circuits connected in a series arrangement. There is only one path for current to flow from the DC voltage source

10、. Therefore, the field is wound of relatively few turns of large diameter wire, giving the field a low resistance. Changes in load applied to the motor shaft cause changes in the current through the field. If the mechanical load increases, the current also increases. The increased current creates a

11、stronger magnetic field. The speed of a series motor varies from very fast at no load to very slow at heavy loads. Since large currents may flow through the low-resistance field, the series motor produces a high-torque output. Series motors are used where heavy loads must be moved and speed regulati

12、on is not important. A typical application is for automobile starter motors.串励式直流电动机,如图1-5A-2所示,电枢和激磁电路串联连接。仅有一个通路供电流从直流电压源流出。因此,激磁绕组匝数相对少、导线直径大,以使激磁绕组阻抗低。电机轴上负载的变化引起通过激磁绕组电流的变化。当负载从零增加到很大时,串励式电机的转速从很高变化到很低。如果机械负载增加,电流也增加。增加的电流建立了更强的磁场。由于大电流可以流过低阻抗的激磁绕组,串励式电动机产生一个高转矩输出。串励式电动机用于启动重负载,而速度调节并不重要的场合。一个典

13、型应用是车辆启动电机。Shunt-wound DC Motor并励式直流电动机Shunt-wound DC motors are more commonly used than any other type of DC motor. As shown in Fig. 1-5A-3, the shunt-wound DC motor has field coils connected in parallel with its armature. This type of DC motor has field coils which are wound for many turns of smal

14、l-diameter wire and have a relatively high resistance. Since the field is a high-resistant parallel path of the circuit of the shunt motor, a small amount of current flows through the field. A strong electromagnetic field is produced due to the many turns of wire that form the field windings.并励式直流电动

15、机是最常用的一种直流电机。这种直流电机的激磁绕组匝数多、导线直径小,因而阻抗相对比较高。由于激磁绕组是并励式电动机电路的高阻抗并联通道,流过激磁绕组的电流很小。由于形成激磁绕组的导线的匝数多,产生的电磁场很强。A large majority (about 95% of the current drawn by the shunt motor flows in the armature circuit. Since the current has little effect on the strength of the field, motor speed is not affected ap

16、preciably by variations in load current. The relationship of the currents that flow through a DC shunt motor is as follows:并励式电动机的大部分电流(大约95%流过电枢电路。由于电流对磁场强度几乎没有什麽影响,电机转速不受负载电流变化的影响。流过并励式直流电动机的电流关系如下:IL=Ia+IfWhere ILtotal current drawn from the power source;Ia armature current;If field current.公式中,I

17、L电机总电流Ia 电枢电流If 激磁电流The field current may be varied by placing a variable resistance in series with the field windings. Since the current in the field circuit is low, a low-wattage rheostat may be used to vary the speed of the motor due to the variation in field resistance.As field resistance increa

18、ses, field current will decrease. A decrease in field current reduces the strength of the electromagnetic field. When the field flux is decreased, the armature will rotate faster, due to reduced magnetic-field interaction.3 Thus the speed of a DC shunt motor may be easily varied by using a field rhe

19、ostat.通过在激磁绕组中串联一个可变电阻可以题解激磁电流。由于激磁回路电流小,低功耗可变电阻器可用于改变激磁绕组阻抗,进而改变电机转速。激磁阻抗增加,几次电流会减少。励磁电流的减小会使磁场减弱。当磁通减少时,转子会由于与减弱的磁场相互作用而加速旋转。因此使用励磁变阻器,并励式直流电动机的转速很容易调节。The shunt-wound DC motor has very good speed regulation. The speed does decrease slightly when the load increases due to the increase in voltage d

20、rop across the armature. Due to its good speed regulation characteristic and its ease of speed control, the DC shunt motor is commonly used for industrial applications. Many types of variable-speed machine tools are driven by DC shunt motors.并励式直流电动机具有优良的转速调节功能。当负载增加时,由于增加了电枢绕组上的压降,转速稍微有一点降低。由于它的优良的

21、转速调节特性和转速控制的简易性,并励式直流电动机通常用于工业场合。许多种可调速机床由并励式直流电动机驱动。Compound-wound DC Motors复励式直流电动机The compound-wound DC motor shown in Fig. 1-5A-4, has two sets of field windings, one in series with the armature and one in parallel. This motor combines the desirable characteristics of the series-wound and shunt-

22、wound motors. There are two methods of connecting compound motors: cumulative and differential. A cumulative compound DC motor has series and shunt fields that aid each other. Differential compound DC motors have series and shunt fields that oppose each other. There are also two ways in which the se

23、ries windings are placed in the circuit. One method is called a short shunt (see Fig. 1-5A-4, in which the shunt field is placed across the armature. The long-shunt method has the shunt field winding placed across both the armature and the series field (see Fig. 1-5A-4.图1-5A-4所示的复励式直流电动机有两个激磁绕组,一个与电

24、枢绕组串联,一个与电枢绕组并联。这种电机综合了串励式电机和并励式电机的预期特性。复励式电动机有两种连接方法:累加与差动。累加复励式直流电动机的串联和并联绕组的激磁方向一致。差动直流电动机的串联和并联绕组的激磁方向相反。串联绕组的连接方法有两种。一种方法较短并联(见图1-5A-4,这种方法是将并联绕组跨接在电枢绕组两端。长并联方法是将并联绕组跨接在电枢绕组和串联绕组的两端(见图1-5A-4。Compound motors have high torque similar to a series-wound motor, together with good speed regulation si

25、milar to a shunt motor. Therefore, when good torque and good speed regulation are needed, the compound-wound DC motor can be used.A major disadvantage of a compound-wound motor is its expense.复励式电机具有类似于串励式电机的高转矩,同时也具有类似于复励式电机的优良的速度调节。因此,当既需要良好的转矩特性又需要良好的速度调节时可采用复励式直流电动机。复励式直流电动机的一个主要缺点价格贵。DC Motor S

26、peed-torque Characteristics直流电机速度-转矩特性In many applications, DC motors are used to drive mechanical loads.Some applications require that the speed remain constant as the mechanical load applied to the motor changes. On the other hand, some applications require that the speed be controlled over a wide

27、 range. An engineer who wishes to use a DC motor for a particular application must therefore know the relation between torque and speed of the machine.在许多应用场合,滞留电机用于驱动机械负载。某些应用场合要求电机驱动的机械负载变化时,电机的转速保持恒定。另一方面,某些应用场合要求调速范围宽。想把直流电机用于特定场合的工程师必须了解电机的转矩和速度之间的关系。Initially our remarks are confined to the shunt motor, but a similar line of reasoning applies for the others. For our purposes the two pertinent equations are those for torque and current. Thus首先我们讨论并励式电机,再把这种方法用于其它电机。为此,两个相关的公式是转矩和电流公式。因此Fig.1-5A-5 sho