English to Chinese Tech/Engineering Mechanics / Mech Engineering 自动化

One type of semiconductor is the SCR (silicon controller rectifier) which will be connected to the AC line voltage. This type of device is usually employed where large amounts of power must be regulated, motor inductance is relatively high and accuracy in speed is not critical (such as constant speed devices for fans, blowers, conveyor belts). Power out of the SCR, which is available to run the motor, comes in discrete pulses. At low speeds a continuous stream of narrow pulses is required to maintain speed. If an increase in speed is desired, the SCR must be turned on to apply large pulses of instant power, and when lower speeds are desired, power is removed and a gradual coasting down in speed occurs. A good example would be when one car is towing a second car. The driver in the first car is the SCR device and the second car, which is being towed is the motor/load.

其中一类半导体是连接到交流线电压的可控硅（SCR） 。这种设备通常运用在必须对大量的电力加以调节，电机电感相对较高，以及速度精度不太重要的地方（如风扇、鼓风机和传送带的恒速装置 ）。由可控硅输出的用以运行电机的电源为离散脉冲。在低转速时，窄脉冲连续流 必须保持一定的速度。如果需要增加速度，必须打开可控硅，施加大量的瞬间脉冲电源，而当需要较低的速度时 ，电源被移走，速度逐步向下滑。一辆车拖着第二辆车就是一个很好的例子。第一辆汽车的驱动机是可控硅设备，而被拖走的第二辆车是马达/负载。

come in 在这儿怎么理解？是电源以什么方式运行的意思吗？