Q&A on common problems of diesel generator set
发布时间：2022-07-02
1. What are the conditions for the parallel operation of two generator sets? What device is used to complete the parallel operation?
Answer: the condition for parallel operation is that the voltage, frequency and phase of the two machines are the same at the moment Generator set is commonly known as "three Simultaneities" Use special parallel device to complete parallel operation It is generally recommended to adopt fully automatic parallel cabinet Try not to parallelize manually The success or failure of manual paralleling depends on human experience Based on more than 20 years of experience in power work, the author boldly said that the reliable success rate of manual paralleling of diesel generators is 0 We must not apply the concept of manual paralleling to the small power supply system of the city TV University, because the protection level of the two is completely different
2. What are the reasons for the high water temperature alarm and shutdown so that it cannot be used?
Answer: the water tank is leaking or insufficient; The water temperature sensor is damaged; The dirt in the water channel of the water tank is too thick or the radiator is greasy;
The fan belt is excessively worn and the pressure is insufficient; The water pump is worn and the water volume of the pump is insufficient; The opening angle of thermostat is not enough, and it is stuck; The cylinder gasket is damaged, and the water channel is connected with the cylinder; The cylinder liner is worn too much and local water seepage occurs; The ventilation of the machine room does not meet the requirements; Overload operation of engine; (including engine fatigue) excessive fuel supply
3. Why must the generator (electric ball) working chamber be clean?
Answer: if the diesel engine absorbs dirty air, its power will decrease; If the generator sucks in sand, dust and other impurities, the gap between the stator and rotor will be damaged, which will lead to burning
4. What level of energy does electric energy belong to? What are the characteristics of AC?
Answer: electric energy belongs to secondary energy. Alternating current is converted from mechanical energy and direct current is converted from chemical energy. The characteristic of alternating current is that it cannot be stored. Now it is found to be used
5. Why does the diesel engine smoke black?
Answer: when the diesel engine is under high load, the exhaust easily emits black smoke At present, the natural process of black smoke is not completely clear. It is generally believed that when the load of the diesel engine is high, the fuel injected into the combustion chamber increases, the temperature in the combustion chamber is higher, and the diesel engine mixture is uneven, which will cause the combustion of insufficient air in local areas of the combustion chamber, and the fuel decomposes and polymerizes to form soot (carbon black) under the condition of high temperature and hypoxia Soot is not pure carbon, but a polymer. The main component is carbon (more than 85%), but it also contains a small amount of oxygen, hydrogen and ash, and its composition changes with the load of the diesel engine Collect the soot through the filter and observe it under the electron microscope. It can be seen that the diameter of large soot particles is about 0.05mm The high-temperature cracking reaction of combustion in diesel engine is inevitable, especially in the diesel engine with space mixed combustion, the high-temperature gas surrounds the liquid oil droplets, resulting in the most favorable conditions for the cracking reaction. The high-speed photography of the combustion process confirms that a large amount of black smoke will appear around the top dead center, but in general, the soot can find air in the subsequent combustion and burn completely, so that the exhaust is free of black smoke However, if the cylinder air is insufficient and the mixing process is slow, the temperature of the negative cylinder decreases due to expansion, and the carbon cannot be burned and aggregated into soot The formation of soot makes the combustion incomplete, the economy of the diesel engine decreases, the exhaust temperature increases, the exhaust emits black smoke, the surface area of the combustion chamber is carbon, and the load cannot be further improved Carbon deposition will also cause piston ring or piston seizure, valve seizure and other faults Therefore, the diesel engine is not allowed to work under overload for a long time
6. Why is there water in the oil tank and how to prevent it?
Answer: qualified fuel will not contain impurities and moisture when leaving the factory, but dust, dirt and moisture will be mixed more or less during transportation and storage; When the fuel tank is not full, the water in the air in the tank is easy to form condensate droplets and mix into the fuel The following points should be paid attention to in the use and storage of fuel oil:
1) The fuel should be stored in the fuel tank for more than 24 hours to precipitate water and impurities before use;
2) Try to fill the daily oil tank after each work, so as to prevent the water in the air of the oil tank from mixing into the fuel;
3) When filling oil, first wipe the funnel and the end cover of the oil tank. When using the hand pump, be careful not to pump out the low sediment together;
4) Regularly open the drain cock of the oil tank to remove water and sediment
7. What fault can cause the accident that the transmission gear of the starting motor of the motor (electric ball) group hits the teeth?
Answer: the battery power is insufficient and the battery temperature is too high; Starter motor relay does not work; The transmission gear of the starting motor cannot mesh with the flywheel ring gear; The starting motor is engaged, and the diesel engine cannot rotate or rotates weakly; The starting motor does not rotate; Start failure; The diesel engine cannot be separated from the starting motor after operation;
8. What are the main reasons for AVR damage?
Answer: AVR circuit consists of three parts: rectifier main circuit, voltage detection circuit and comparison control circuit; Excluding the possibility of damage caused by the quality of the original electrical components, in the whole AVR circuit, the operating frequency of the main circuit and the comparison control circuit changes the most; Among them, the rectifier bridge of the main circuit and the transistor in the comparison circuit change more frequently, and its damage proportion accounts for more than 90% of the damage rate of the whole AVR; Since the AVR on the imported generator is a non disassembly and repair accessory, it needs to be replaced if it is damaged. Therefore, we mainly analyze the causes of AVR damage on the generator. It is most important to avoid AVR damage as far as possible. As long as it is used properly, the service life of AVR can be improved The more stable the generator voltage is, the smaller the variation frequency in AVR is; The smaller the switching action of the transistor in the comparison circuit, the smaller the probability of AVR damage; The output load is relatively stable. The smaller the change frequency in the AVR, the smaller the switching action of the transistor in the comparison circuit, and the smaller the probability of AVR damage; The more stable the speed of diesel engine is, the smaller the oscillation impact of variable current on AVR is; Frequent "traveling block" and overload, and too large difference between three-phase loads are the main reasons for AVR damage; If the generator set with E, F and C fuel systems is selected, the use of AVR will be more reliable due to small frequency variation
9. What is the so-called reverse power transmission? What are the two serious consequences?
A: the situation of self-contained generator (electric ball) transmitting power to the municipal grid is called reverse transmission There are two serious consequences:
If the municipal power grid is not powered off, the power supply of the municipal power grid and the power supply of the self-contained generator will not be synchronized, and the unit will be destroyed If the self - provided generator has a large capacity, it will also cause the municipal power grid to vibrate b) The municipal power grid has been cut off and is being tested, and its own generator is powered back It will electrocute the inspection staff of the power supply section
10. Why can't I turn off and start up with load?
Answer: shutdown with load is an emergency shutdown, which has a great impact on the unit Starting with load is illegal operation, which will cause damage to power generation equipment and electrical equipment
11. How to match the power of ups and diesel generator to ensure the stable output of UPS?
Answer:
1) UPS is generally expressed by apparent power kVA. Multiply it by 0.8 to convert it into kW, which is consistent with the active power of the generator
2) If a general generator is used, the power of the generator is determined by multiplying the active power of ups by 2, that is, the generator power is twice the power of ups
3) If the generator with PMG (permanent magnet excitation) is used, the generator power is determined by multiplying the UPS power by 1.2, that is, the generator power is 1.2 times the UPS power
12. The frequency and voltage of a generator set are unstable. Is the problem engine or generator?
Answer: it's the engine
13. The problem of a generator set with stable frequency and unstable voltage lies in the engine or generator?
Answer: it's the generator (electric ball)
14. What is the matter of generator loss of excitation and how to deal with it?
Answer: the generator is not used for a long time, which leads to the loss of residual magnetism contained in the iron core before leaving the factory, and the excitation coil cannot establish the due magnetic field. At this time, the engine operates normally but cannot generate electricity. This kind of phenomenon is new Or there are many units that are not used for a long time Treatment method:
If there is an excitation button, press the excitation button once. 2) if there is no excitation button, magnetize it with a battery; 3) With a bulb load, overspeed for a few seconds
15. What is the loaded sequence after power on?
Answer: the load is carried from large to small
16. What is the unloading sequence before the machine?
Answer: the load is unloaded from small to large, and finally shut down
17. How is the loss of excitation of generator (electric ball) and how to deal with it?
Answer: the generator (electric ball) is not used for a long time, which leads to the loss of residual magnetism contained in the iron core before leaving the factory, and the excitation coil cannot establish the due magnetic field. At this time, the engine operates normally but cannot generate electricity. There are many new machines or units that are not used for a long time Treatment method:
1) If there is an excitation button, press the excitation button once
2) If there is no excitation button, magnetize it with a battery
3) With a bulb load, overspeed for a few seconds
18. What is the so-called three-phase four wire system?
Answer: there are 4 outgoing lines of the generator set, of which 3 are live lines and 1 is zero line The voltage between live wires is 380V 220V between live line and neutral line
19. What's the matter with three-phase short circuit? What will happen?
Answer: there is no load between the live wires, and the direct short circuit is a three-phase short circuit The consequences are very terrible, and serious will lead to machine destruction and human death
Answer: the condition for parallel operation is that the voltage, frequency and phase of the two machines are the same at the moment Generator set is commonly known as "three Simultaneities" Use special parallel device to complete parallel operation It is generally recommended to adopt fully automatic parallel cabinet Try not to parallelize manually The success or failure of manual paralleling depends on human experience Based on more than 20 years of experience in power work, the author boldly said that the reliable success rate of manual paralleling of diesel generators is 0 We must not apply the concept of manual paralleling to the small power supply system of the city TV University, because the protection level of the two is completely different
2. What are the reasons for the high water temperature alarm and shutdown so that it cannot be used?
Answer: the water tank is leaking or insufficient; The water temperature sensor is damaged; The dirt in the water channel of the water tank is too thick or the radiator is greasy;
The fan belt is excessively worn and the pressure is insufficient; The water pump is worn and the water volume of the pump is insufficient; The opening angle of thermostat is not enough, and it is stuck; The cylinder gasket is damaged, and the water channel is connected with the cylinder; The cylinder liner is worn too much and local water seepage occurs; The ventilation of the machine room does not meet the requirements; Overload operation of engine; (including engine fatigue) excessive fuel supply
3. Why must the generator (electric ball) working chamber be clean?
Answer: if the diesel engine absorbs dirty air, its power will decrease; If the generator sucks in sand, dust and other impurities, the gap between the stator and rotor will be damaged, which will lead to burning
4. What level of energy does electric energy belong to? What are the characteristics of AC?
Answer: electric energy belongs to secondary energy. Alternating current is converted from mechanical energy and direct current is converted from chemical energy. The characteristic of alternating current is that it cannot be stored. Now it is found to be used
5. Why does the diesel engine smoke black?
Answer: when the diesel engine is under high load, the exhaust easily emits black smoke At present, the natural process of black smoke is not completely clear. It is generally believed that when the load of the diesel engine is high, the fuel injected into the combustion chamber increases, the temperature in the combustion chamber is higher, and the diesel engine mixture is uneven, which will cause the combustion of insufficient air in local areas of the combustion chamber, and the fuel decomposes and polymerizes to form soot (carbon black) under the condition of high temperature and hypoxia Soot is not pure carbon, but a polymer. The main component is carbon (more than 85%), but it also contains a small amount of oxygen, hydrogen and ash, and its composition changes with the load of the diesel engine Collect the soot through the filter and observe it under the electron microscope. It can be seen that the diameter of large soot particles is about 0.05mm The high-temperature cracking reaction of combustion in diesel engine is inevitable, especially in the diesel engine with space mixed combustion, the high-temperature gas surrounds the liquid oil droplets, resulting in the most favorable conditions for the cracking reaction. The high-speed photography of the combustion process confirms that a large amount of black smoke will appear around the top dead center, but in general, the soot can find air in the subsequent combustion and burn completely, so that the exhaust is free of black smoke However, if the cylinder air is insufficient and the mixing process is slow, the temperature of the negative cylinder decreases due to expansion, and the carbon cannot be burned and aggregated into soot The formation of soot makes the combustion incomplete, the economy of the diesel engine decreases, the exhaust temperature increases, the exhaust emits black smoke, the surface area of the combustion chamber is carbon, and the load cannot be further improved Carbon deposition will also cause piston ring or piston seizure, valve seizure and other faults Therefore, the diesel engine is not allowed to work under overload for a long time
6. Why is there water in the oil tank and how to prevent it?
Answer: qualified fuel will not contain impurities and moisture when leaving the factory, but dust, dirt and moisture will be mixed more or less during transportation and storage; When the fuel tank is not full, the water in the air in the tank is easy to form condensate droplets and mix into the fuel The following points should be paid attention to in the use and storage of fuel oil:
1) The fuel should be stored in the fuel tank for more than 24 hours to precipitate water and impurities before use;
2) Try to fill the daily oil tank after each work, so as to prevent the water in the air of the oil tank from mixing into the fuel;
3) When filling oil, first wipe the funnel and the end cover of the oil tank. When using the hand pump, be careful not to pump out the low sediment together;
4) Regularly open the drain cock of the oil tank to remove water and sediment
7. What fault can cause the accident that the transmission gear of the starting motor of the motor (electric ball) group hits the teeth?
Answer: the battery power is insufficient and the battery temperature is too high; Starter motor relay does not work; The transmission gear of the starting motor cannot mesh with the flywheel ring gear; The starting motor is engaged, and the diesel engine cannot rotate or rotates weakly; The starting motor does not rotate; Start failure; The diesel engine cannot be separated from the starting motor after operation;
8. What are the main reasons for AVR damage?
Answer: AVR circuit consists of three parts: rectifier main circuit, voltage detection circuit and comparison control circuit; Excluding the possibility of damage caused by the quality of the original electrical components, in the whole AVR circuit, the operating frequency of the main circuit and the comparison control circuit changes the most; Among them, the rectifier bridge of the main circuit and the transistor in the comparison circuit change more frequently, and its damage proportion accounts for more than 90% of the damage rate of the whole AVR; Since the AVR on the imported generator is a non disassembly and repair accessory, it needs to be replaced if it is damaged. Therefore, we mainly analyze the causes of AVR damage on the generator. It is most important to avoid AVR damage as far as possible. As long as it is used properly, the service life of AVR can be improved The more stable the generator voltage is, the smaller the variation frequency in AVR is; The smaller the switching action of the transistor in the comparison circuit, the smaller the probability of AVR damage; The output load is relatively stable. The smaller the change frequency in the AVR, the smaller the switching action of the transistor in the comparison circuit, and the smaller the probability of AVR damage; The more stable the speed of diesel engine is, the smaller the oscillation impact of variable current on AVR is; Frequent "traveling block" and overload, and too large difference between three-phase loads are the main reasons for AVR damage; If the generator set with E, F and C fuel systems is selected, the use of AVR will be more reliable due to small frequency variation
9. What is the so-called reverse power transmission? What are the two serious consequences?
A: the situation of self-contained generator (electric ball) transmitting power to the municipal grid is called reverse transmission There are two serious consequences:
If the municipal power grid is not powered off, the power supply of the municipal power grid and the power supply of the self-contained generator will not be synchronized, and the unit will be destroyed If the self - provided generator has a large capacity, it will also cause the municipal power grid to vibrate b) The municipal power grid has been cut off and is being tested, and its own generator is powered back It will electrocute the inspection staff of the power supply section
10. Why can't I turn off and start up with load?
Answer: shutdown with load is an emergency shutdown, which has a great impact on the unit Starting with load is illegal operation, which will cause damage to power generation equipment and electrical equipment
11. How to match the power of ups and diesel generator to ensure the stable output of UPS?
Answer:
1) UPS is generally expressed by apparent power kVA. Multiply it by 0.8 to convert it into kW, which is consistent with the active power of the generator
2) If a general generator is used, the power of the generator is determined by multiplying the active power of ups by 2, that is, the generator power is twice the power of ups
3) If the generator with PMG (permanent magnet excitation) is used, the generator power is determined by multiplying the UPS power by 1.2, that is, the generator power is 1.2 times the UPS power
12. The frequency and voltage of a generator set are unstable. Is the problem engine or generator?
Answer: it's the engine
13. The problem of a generator set with stable frequency and unstable voltage lies in the engine or generator?
Answer: it's the generator (electric ball)
14. What is the matter of generator loss of excitation and how to deal with it?
Answer: the generator is not used for a long time, which leads to the loss of residual magnetism contained in the iron core before leaving the factory, and the excitation coil cannot establish the due magnetic field. At this time, the engine operates normally but cannot generate electricity. This kind of phenomenon is new Or there are many units that are not used for a long time Treatment method:
If there is an excitation button, press the excitation button once. 2) if there is no excitation button, magnetize it with a battery; 3) With a bulb load, overspeed for a few seconds
15. What is the loaded sequence after power on?
Answer: the load is carried from large to small
16. What is the unloading sequence before the machine?
Answer: the load is unloaded from small to large, and finally shut down
17. How is the loss of excitation of generator (electric ball) and how to deal with it?
Answer: the generator (electric ball) is not used for a long time, which leads to the loss of residual magnetism contained in the iron core before leaving the factory, and the excitation coil cannot establish the due magnetic field. At this time, the engine operates normally but cannot generate electricity. There are many new machines or units that are not used for a long time Treatment method:
1) If there is an excitation button, press the excitation button once
2) If there is no excitation button, magnetize it with a battery
3) With a bulb load, overspeed for a few seconds
18. What is the so-called three-phase four wire system?
Answer: there are 4 outgoing lines of the generator set, of which 3 are live lines and 1 is zero line The voltage between live wires is 380V 220V between live line and neutral line
19. What's the matter with three-phase short circuit? What will happen?
Answer: there is no load between the live wires, and the direct short circuit is a three-phase short circuit The consequences are very terrible, and serious will lead to machine destruction and human death
