In the industrial field, diesel generator sets are indispensable backup power equipment. Whether dealing with sudden power outages or providing reliable power support when the power grid is unstable, diesel generator sets play an important role. To ensure that the generator set runs efficiently and stably, properly adjusting its speed is one of the key links. This article will delve into the importance of diesel generator set speed adjustment, the different types of governors and their working principles, as well as specific adjustment methods and steps, to help you better manage and maintain generator sets.
The speed of a diesel generator set is usually expressed by the number of crankshaft revolutions per minute, namely r/min. Different usage scenarios have different requirements for the speed of diesel generator sets. For example, fixed equipment such as diesel generator sets and pump units usually use constant-speed diesel engines. Taking the 50Hz diesel generator set as an example, its speed is 1500 r/min. Maintaining a reasonable working speed range is crucial for diesel generator sets, because it can effectively reduce wear and extend the service life of the unit.
When the diesel generator set starts, the crankshaft speed is low, the oil pump cannot supply oil in time, and coupled with the low oil temperature and high viscosity, it is difficult for the friction surfaces to establish good liquid lubrication, and the wear will be very serious. As speed and load increase, friction will also increase accordingly. This is because when the load increases, the unit pressure on the friction surface increases and the heat condition worsens; when the speed increases, the number of friction occurrences per unit time also increases. At the same power, an increase in speed causes more wear than an increase in load. Too low a speed will also lead to increased wear because it cannot ensure good liquid lubrication conditions. In addition, when the diesel generator set frequently accelerates, decelerates, stops, and starts, due to frequent changes in speed and load, poor lubrication conditions, and unstable thermal states, wear will also increase. Therefore, when using a diesel generator set, adjusting the speed to a reasonable range can reduce wear and maximize performance.
The speed control of a diesel generator set cannot be separated from the governor, which is the key component to maintain stable operation. The governor monitors and adjusts the engine speed to ensure it maintains the set speed under different load conditions. According to working principles and technical characteristics, governors are mainly divided into three types: mechanical governors, electronic governors, and hydraulic governors. The following introduces their principles, advantages, and disadvantages.
The mechanical governor is one of the earliest speed control devices applied to diesel generator sets. It mainly works based on the principle of centrifugal force, with a pair of flyweights (or flyballs). When the speed of the diesel generator set changes, the centrifugal force of the flyweights also changes. For example, when the speed increases, the centrifugal force of the flyweights increases, swinging outward, and through a lever mechanism reduces the fuel supply of the injection pump; conversely, when the speed decreases, the centrifugal force of the flyweights decreases, retracting inward, and increases the fuel supply.
The mechanical governor is usually equipped with an adjusting screw or knob, which is used to adjust the preload of the governor spring. By rotating the screw or knob, the initial set speed of the governor can be changed. For example, rotating the adjusting screw clockwise will increase the spring preload and raise the working speed set point; rotating counterclockwise will lower it. During operation, if small fluctuations in speed are found, some mechanical governors are also equipped with fine-tuning devices. This may be a small adjusting nut or a movable stopper, which can subtly adjust the movement range of the flyweights, thus better controlling the fuel supply and stabilizing the speed. However, such fine-tuning is relatively complex and requires some experience and skill.
The advantages of the mechanical governor are simple structure, high reliability, no need for an external power supply, and the ability to work in relatively harsh environments. However, its adjustment accuracy is relatively low, the response speed is slow, and after long-term use, wear of mechanical parts may cause performance decline.
With technological development, the electronic governor has gradually become the mainstream speed control device for diesel generator sets. The electronic governor uses electronic sensors to monitor the speed of the diesel generator set. The sensor converts the speed signal into an electrical signal and transmits it to the electronic controller. The electronic controller compares and calculates the preset speed value with the actual speed signal, and then controls the actuator (such as the electronic fuel injection system) to adjust the fuel supply. For example, when the actual speed is higher than the preset speed, the electronic controller reduces the fuel injection pulse width to lower the fuel supply and reduce the speed.
On the control panel of the electronic governor, there are digital keys or knobs to directly input or adjust the preset speed value. The operator only needs to follow the instructions and input the required speed, and the electronic governor will automatically adjust the fuel supply to reach the set speed. Many advanced electronic governors can be integrated with the monitoring system of the generator set to achieve automatic adjustment. For example, in parallel operation with the grid, the electronic governor can automatically adjust the speed according to grid frequency and load changes. At the same time, through a remote communication interface, operators can configure and adjust the governor from a remote monitoring center, greatly improving convenience and flexibility.
The advantages of the electronic governor are high adjustment accuracy, fast response to load and speed changes, and multiple protection and fault diagnosis functions, such as overspeed protection and underspeed protection. However, its structure is complex, requiring high reliability of electronic components, and it needs a stable power supply. In environments with high temperature, humidity, or strong electromagnetic interference, faults may occur.
The hydraulic governor is a speed control device that uses fluid pressure to transmit power and control signals. It mainly consists of an oil pump, pressure cylinder, and servo motor. When the generator speed changes, signals generated by the centrifugal mechanism or other sensors control the flow direction and pressure of the hydraulic oil, thereby driving the servo motor to adjust the fuel supply of the injection pump. For example, when the speed rises, the hydraulic system drives the servo motor to reduce the opening of the fuel pump, lowering the fuel supply.
The hydraulic governor has devices such as relief valves and throttle valves to adjust system parameters. By adjusting the set pressure of the relief valve, the working pressure range of the hydraulic system can be changed, thus affecting the force and speed of the servo motor. Adjusting the throttle valve can control oil flow, thereby affecting response speed. The hydraulic governor also has mechanisms similar to mechanical governors to set initial speed and adjustment range. For example, by adjusting the tension of the control spring, the base speed can be set. When the actual speed deviates, the hydraulic system adjusts according to the deviation.
The hydraulic governor offers good stability and regulation accuracy, can output larger adjustment forces, and is suitable for high-power diesel generator sets. However, it has a complex structure and requires regular inspection of oil quality and sealing. Troubleshooting hydraulic system faults is relatively difficult.
After understanding the types and working principles of governors, we can look at how to adjust the speed of diesel generator sets. Proper speed adjustment not only improves efficiency but also extends service life.
Before adjustment, sufficient preparation must be made. First, ensure the generator set is in good working condition, check oil, coolant, and all connections. Next, familiarize yourself with the control panel and governor operation interface, understanding each parameter and its range. Finally, prepare necessary tools such as screwdrivers and multimeters.
Potentiometer Adjustment
If the control panel has a speed adjustment potentiometer, loosen the lock nut, adjust it to the middle position, and then fix the lock nut.
Adjust the potentiometers on the electronic speed controller to: Gain 20%, Integral (I) 20%, Derivative (D) 30%, Droop 0%.
Rotate the speed potentiometer counterclockwise to the lock position, then clockwise for 10 turns, setting it in the middle position.
Start and Warm Up
Start the generator and adjust the speed to 1500 r/min, allowing it to warm up to proper temperature. This step is crucial to ensure accurate and stable adjustment.
Gain Adjustment
Rotate the Gain potentiometer clockwise until unstable operation occurs. Then slowly rotate counterclockwise until stable operation returns.
If there are D and I potentiometers, adjust them in the same way.
Check and Correct Speed Deviation
Verify if the speed deviates and adjust it back to 1500 r/min under no-load conditions.
Adjust the droop characteristic under no-load to ensure proper working frequency at full load.
Dynamic Response Test
Under no-load, rotate the Gain potentiometer clockwise until oscillation occurs, then slowly rotate counterclockwise until stable.
Short-circuit terminals 7 and 10 on the controller momentarily to disturb it. If the speed returns to normal after three decreasing oscillations, the gain is appropriate.
Apply load and unload to confirm dynamic response. If unsatisfactory, repeat adjustments.
Full-Load Adjustment
After gain adjustment, apply full load and adjust the speed potentiometer so that frequency reaches the required value.
When adjusting the speed of a diesel generator set, the following points must be noted to ensure safety and effectiveness.
Safety First: During speed adjustment, always prioritize operator safety. Avoid contact with rotating parts while the unit is running to prevent accidents.
Gradual Adjustment: Adjust the potentiometer gradually instead of making large changes at once, as sudden adjustments may cause operational instability. After each adjustment, carefully observe the unit’s operating condition to ensure the result meets expectations.
Record Parameters: During the adjustment process, record each parameter setting along with the operating status of the unit. This helps in quickly identifying causes in case of problems and provides a reference for future maintenance and adjustments.
Regular Maintenance: Regularly inspect and maintain the governor and related components to ensure proper functioning. For mechanical governors, check for wear of mechanical parts; for electronic governors, inspect the condition of electronic components; for hydraulic governors, check the quality of hydraulic oil and the sealing performance of the system.
Professional Guidance: If you are not familiar with speed adjustment, it is advisable to consult professional technicians or refer to the equipment’s operation manual. Correct adjustment methods can effectively extend the service life of the generator set and improve its operating efficiency.
Proper speed adjustment of diesel generator sets is vital for efficient and stable operation. By understanding different types of governors and their principles, and mastering correct adjustment methods and steps, you can reduce wear and improve efficiency. In practice, always prioritize safety, adjust gradually, and keep detailed records and maintenance. This article aims to help you better manage and maintain diesel generator sets, ensuring reliable operation under all working conditions.
