2014.04.05【英译中】交流发电机②

猫四狗八 (ho) 路人甲
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发表于:2014-04-05 19:31 [只看楼主] [划词开启]

5. So far, alternator construction has considered the armature rotating and the field coils stationary; the same electricity generating effects is produced if the reverse occurs. That is, the field coils rotate and the armature is stationary. This is in fact the arrangement adopted for a large, heavy duty alternator.

5. 目前,交流发电机的结构都是电枢旋转磁场静止的,如果是相反的情况(磁场旋转而电枢静止)也同样能产生电流,这多用于大功率发电机。

 

6 The field current supply in order machines comes from a low voltage direct current generator or exciter on the same shaft as the alternator. Modern machines however are either statically excited or of the high speed brushless type. The exciter is required to operate to counter the effects of power factor for a given load. The power factor is a measure of the phase difference between voltage and current and is expressed as the cosine of the phase angle. With a purely resistance load, the voltage and the current are in phase, giving power factor of one. The power consumed is therefore the product of voltage and current. Inductive or capacitive loads, combined with resistance load, produce lagging or leading power factors which have a value less than one. The power consumed is the product of current, voltage and the power factor. The alternating current generator supplying a load has a voltage drop resulting from the load. When the load has a lagging power factor, this voltage drop is considerable. Therefore the exciter, in maintaining the alternator voltage, must vary with load current and also the power factor. The speed change of the prime mover must be taken into account.

6. 磁场电力的供应种类有低压直流发电机或励磁机与发电机连接在同一个轴承上作为发电机。现代的机器一般是静励磁或高速无电刷的。励磁机需要能抵抗负载功率因数带来的影响。功率因数是指电流和电压之间相位差的度量,用相位角的余弦来表示。纯电阻电路中,电压和电流是同相位的,功率因数是1,电功就是电压和电流的乘积。结合电阻的电感或电容电路,功率因数是滞后或超前的,大小是小于1的,电功就是电压电流和功率因数的乘积。交流发电机提供给电路的电压有一个很大的压降,当电路的功率因数是滞后时,压降就非常大。因此,励磁机为了保持发电的电压,就必须随着随电路调整,此时就要考虑改变原动机的速度。

 

7 Hand control of excitation is difficult, so use is made up of a automatic voltage regulator (AVR). The AVR consists basically of a circuit fed from the alternator output voltage which detects small changes in voltage and feeds a signal to an amplifier which changes the excitation to correct the voltage. Stabilizing features are also incorporated in the circuits to avoid “hunting” (constant voltage fluctuations) or overcorrecting.

7 .手动控制励磁机很困难,所以需要用到自动变压调节器,它是由发电机的输出电压来供电的,能够发现电压极小的变化,然后给放大器一个信号,改变励磁调整电压。电路中还有稳压元件,除了能避免振荡还能避免过度调节。

 

8. The statically excited alternator has a static excitation system instead of a DC exciter. This type of alternator will more accept the sudden loading by direct on-line starting of large squirrel cage motors. The static excitation system uses transformers and rectifiers to provide series and shunt components for the alternator field, that is, it is compounded. Brushes and slip rings are used to transfer the current to the field coils which are mounted on the rotor. The terminal voltage from the alternator thus gives the no load condition. The compensation necessary for speed variation requires that a voltage regulator be also built into the system.

8.  静励磁发电机有一个静止的励磁系统代替了直流励磁机。这种励磁机能够承受鼠笼式电动机启动带来的突然的负载。静励磁系统用变压器和整流器为交流励磁提供串励和并励分量,这就叫做复励。电刷和滑环将电流传递到转子线圈上。端电压就能实现发电机的空转。为了调节速度变化系统也需要一个电压调节器。


最后编辑于:2014-04-05 19:36
分类: 英语

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