柴油发电机组转速测量保护系统工作原理是什么？ What is the working principle of the speed measurement and protection system for diesel generator sets?

　柴油发电机组转速测量保护系统的工作原理：

　　转速是柴油发电机设备中最基本、最重要的参数之一，起动时的点火转速、运行中的转速调整、超速时的停车保护、甚至负荷的大小也能从转速的大小上得到体现，因此转速测定是柴油发电机监控保护的基础。一般柴油机中转速的测量有二处，一是主机转速的测量，二是涡轮增压器转速的测量。

　　（1） 传感器。传感器是一个近程感应开关，不通过接触就可以工作。它由振荡器、触发器及放大器组成，通过振荡器电路线圈产生一交变电磁场。在金属导体接近传感器时交变磁场就会发生变化，振荡器的输出电压随之发生变化，频率也发生变化。主机转速测量的传感器共有4个。2个测量转速并经速度变送器在CMR盘或OCW盘显示转速，另外2个供调速器使用。

　　（2） 速度变送器。将传感器传输来的频率信号转换成4～20 mA的电流信号，传送给转速表。

　　（3） 转速表。显示转速。

The working principle of the speed measurement and protection system for diesel generator sets:

Speed is one of the most basic and important parameters in diesel generator equipment. The ignition speed during start-up, speed adjustment during operation, parking protection during overspeed, and even the size of the load can also be reflected from the speed. Therefore, speed measurement is the basis of diesel generator monitoring and protection. There are two ways to measure the rotational speed in a typical diesel engine: one is to measure the engine speed, and the other is to measure the turbocharger speed.

(1) Sensors. The sensor is a proximity sensing switch that can operate without contact. It consists of an oscillator, a trigger, and an amplifier, which generate an alternating electromagnetic field through the oscillator circuit coil. When a metal conductor approaches the sensor, the alternating magnetic field will change, and the output voltage of the oscillator will also change, along with the frequency. There are a total of 4 sensors for measuring the speed of the host. Two measure the speed and display it on the CMR or OCW panel through the speed transmitter, while the other two are used for the speed controller.

(2) Speed transmitter. Convert the frequency signal transmitted by the sensor into a 4-20 mA current signal and transmit it to the tachometer.

(3) Tachometer. Display the rotational speed.