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Introduction of Governor in Diesel Generator

Aug. 22, 2018

The function and type of diesel generator set governor


1. The function of the governor of diesel generator set


The function of the governor is to adjust the fuel supply automatically with the change of the external load of the diesel engine within the required speed range of the diesel engine, so as to keep the diesel engine speed basically stable.

Introduction of Governor in Diesel Generator.jpg


When the diesel engine drives other working machinery (such as generator, pump, etc.), if the output torque is equal to the torque (drag moment) required by the working machinery to overcome the working resistance, then the engine is in a stable state (the rotational speed is basically stable). If the resistance moment exceeds the output torque, the speed of the diesel engine will decrease, and the diesel engine will stop working. When the output torque is greater than the resistance moment, the rotational speed will increase, if the new balance is not reached, the rotational speed will continue to rise and the "flying car" accident will occur. Because the resistance moment of the working machine will change frequently with the change of the working condition, it is impossible for the operator to adjust the fuel supply sensitively and in time, so that the output torque of the diesel engine can be adapted to the external resistance. In this way, the speed of the diesel engine will fluctuate violently, thus affecting the normal operation of the working machinery. Therefore, the diesel engine for construction machinery must be equipped with governor. In addition, due to the characteristics of diesel spatter pump itself, it is not easy to maintain stability at idle speed, and it is easy to overspeed or even "fly" at high speed. Therefore, the governor must be installed on the diesel engine to keep its idle speed stable and prevent the phenomenon of "flying car" at high speed.



2. Type of governor

A. According to the different classification of governor regulating mechanism, it can be divided into four types: mechanical type, hydraulic type, pneumatic type and electronic type.


(1) ]mechanical governor

The sensing element of the mechanical governor is a flying block or a flying ball, which directly pushes the actuator. Simple structure, reliable work, widely used in medium and small power diesel engines.


(2) hydraulic speed governor


The pressure governor generally uses the flying block as an inductive element to push the piston to operate the hydraulic server. This governor has small induction elements and strong versatility. A few series of dimensions can be used to meet the requirements of tens to ten thousand horsepower diesel engines. It has good stability, high adjustment precision and large driving force, and is easy to realize automatic control of diesel engine. But the structure is complex, the craft request is high, suitable for the high power diesel engine.



(3) Pneumatic governor


The moving governor uses the diaphragm to induce the change of the vacuum of the inlet pipe, and then to promote the actuating mechanism. The governor has simple structure and high sensitivity at low speed, but the power is decreased due to the throttle valve installed in the intake pipe. Therefore, it is only suitable for low power diesel engines.


(4) electronic governor

The electronic governor converts the change of diesel engine speed into the change of electric quantity, and controls the actuator after sampling and amplifying. This governor can adjust the fuel supply before the speed of diesel engine changes obviously, and obtain high adjusting precision, and realize parallel operation without difference. Mainly used for diesel generator sets.



3. According to the speed range of the governor, it can be divided into three types: single program, two-pole type and whole course type.



(1) Single program governor

A single program governor works only at a certain speed (usually a calibrated speed). Suitable for diesel engine with constant speed, such as driving generator, air compressor, centrifugal pump and so on.



(2) Two-pole governor

The two-pole speed governor works only in the case of idle speed and calibrated speed of diesel engine. Mainly used in cars, to maintain idling stability and prevent high-speed "flying". In other cases, the operator operates the throttle to adjust the fuel supply.


(3 )Whole speed governor


The whole-course governor works in the range of diesel engine speed. After the operator chooses any speed according to the need of the operation, the governor can make the diesel engine work steadily at the speed automatically. It greatly improves the working conditions of the operators under the condition of frequent load changes, and also improves the working quality and production efficiency. Therefore, most construction machinery uses this governor.


The failure of the electronic governor will cause the performance of the diesel engine to decline so that the diesel engine can not run. If it can be clearly judged as the fault of the electronic governor, the power can be replaced by the governor. If it is a fault of diesel engine and its auxiliary system, it is possible to meet the operational requirements through the speed of the diesel engine, and the replacement of electronic governor will not solve the problem. Therefore, the cause of the failure should be analyzed through the comprehensive analysis of the system. One by one, check and check to judge.


Fault Phenomenon

Detection Site

Test Method

Diesel engine can't start

Battery voltage

Measuring the voltage of 5 ~ 6 terminal battery should be 24VDC


1. speed sensor bad installation gap too large


2. Speed sensor cable broken, measured DC resistance should be 300-500 ohms

The actuator cannot open the oil valve completely

Battery voltage

The battery voltage is measured when starting. If the voltage is below the rated working voltage, the battery is undervoltage and the battery needs to be charged.


Clamping phenomenon in the linkage between actuator and rack of oil pump.

Diesel engine speed instability


1. Adjust the stability and gain potentiometer on the controller

2. .The measuring voltage of 14m 7 terminal should be 10 ±0.5 V


Check for loosening of the linkage between actuator and oil pump rack.

Diesel engine overspeed


1. The number of teeth of diesel engine is wrong and the rated speed is too high.

2. Too low gain setting and poor sensitivity, which results in the rotational speed passing in an instant.

3. Malfunction of rotational speed controller should be replaced


1. Check for stuck or loose connection between actuator and oil pump rack

2. The actuator does not match the oil supply zero of the oil pump, and the actuator can't shut off the oil supply after the power is off.

revolution speed transducer

Speed sensor signal error, wiring damage

Turn off the diesel engine before running speed to the option


Speed sensor signal error, wiring damage



Signal of Insufficient magnetic speed sensor: When the rotational speed sensor signal is strong, it can resist the external pulse interference, and the rotational speed controller can measure the RMS signal above 3V output from the rotational speed sensor. When the voltage is lower than 3V, the clearance between the speed sensor and the engine should be reduced (the gap should be less than 0.45mm), which can increase the amplitude of the signal. When the voltage is still below 3 V, check if the magnetic properties of the speed sensor are too weak.



The cable or direct radiation control circuit signal is a great interference source, which will bring bad effect to the side speed system. The speed sensor should be connected with a shielded cable. Since the source of interference is different, it is recommended to use the shielded cable, and the metal plate of the speed controller is grounded or installed in the inner sealed metal clamp to protect against electron radiation. Use metal covers or metal containers to work better. Shielding wire is the most common anti-interference measure. If the generator is equipped with brush, the EDM interference can not be ignored, so special shielding measures should be adopted in the large disturbance environment.



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