FAQs about diesel generator sets

1. What are the conditions for using two generator sets in parallel? What device should be used to complete the parallel operation?
Answer: The condition for parallel use is that the instantaneous voltage, frequency and phase of the two generators are the same. The generator set is commonly known as 'three simultaneous'. Use a parallel device to complete the paralleling work. It is generally recommended to use a fully automatic paralleling cabinet. Try not to use manual paralleling. The success or failure of manual paralleling depends on human experience. The author boldly states that with more than 20 years of experience in electric power work, diesel The reliable success rate of manual paralleling of generators is 0. The concept that a large mains power supply system can be manually paralleled must not be applied to a small power supply system because the protection levels of the two are different.
2. What are the reasons for the high water temperature alarm to shut down the machine and make it unusable?
Answer: The water tank is leaking or the water volume is insufficient; the water temperature sensor is damaged; the dirt in the water channel of the water tank is too thick or the heat sink is too oily; the fan belt is too worn and the pressure is insufficient; the water pump is worn and the pump water volume is insufficient; the opening angle of the thermostat is not enough and it is stuck. Phenomenon: the cylinder gasket is washed out and the water channel is connected with the cylinder; the cylinder liner is excessively worn and local water seeps; the ventilation of the engine room does not meet the requirements; the engine is overloaded; (including engine fatigue) the fuel supply is too large.
3. Why must the working chamber of the generator (electric ball) be kept clean?
Answer: If the diesel engine sucks in dirty air, the power will decrease; if the generator sucks in sand, dust and other impurities, it will damage the insulation between the stator and rotor gaps, or even burn out.
4. Which level of energy does electric energy belong to? What are the characteristics of alternating current?
Answer: Electric energy is a secondary energy source. 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 and is now used.
5. Why does the diesel engine emit black smoke?
Answer: When a diesel engine is under high load, the exhaust will easily emit black smoke. The generation process of black smoke is generally believed that when the diesel engine load is high, more fuel is injected into the combustion chamber, and the temperature in the combustion chamber is higher. In addition, the diesel engine The mixture forms uneven characteristics, which will cause combustion with insufficient air in local areas in the combustion chamber. The fuel will decompose and polymerize under the condition of high temperature and lack of oxygen. Forming soot (carbon black). Soot is not pure carbon, but a polymer. The main component is carbon (more than 85%), but also contains a small amount of oxygen, hydrogen and ash, and its composition changes with the load of the diesel engine. It changes depending on the situation. Pass the black smoke through the filter to collect the carbon smoke and observe it under an electron microscope. You can see that the diameter of the large carbon smoke particles is 0.05mm. Left and right. The high-temperature cracking reaction of combustion in diesel engines is inevitable, especially in diesel engines with spatial mixed combustion. High-temperature gas surrounds liquid oil droplets, creating the most favorable conditions for cracking reactions. High-speed photography of the combustion process confirms , a large amount of black smoke will appear around the top dead center, but under normal circumstances, the soot can find air in the subsequent combustion and burn completely, so that the exhaust is free of black smoke. But if the cylinder If there is insufficient air and the mixing process proceeds slowly, then the cylinder temperature will drop due to expansion, and the carbon will not be burned and will be aggregated into soot. The formation of soot will cause incomplete combustion, the economy of the diesel engine will decrease, the exhaust temperature will increase, and the exhaust will emit smoke. Black smoke and carbon deposits on the surface of the combustion chamber prevent the load from further increasing. Carbon deposits can also cause piston rings or pistons to get stuck, valves to seize, and other failures. Therefore, the diesel engine is not allowed to operate under overload conditions for a long time.
6. Why is there water in the fuel tank and how to prevent it?
Answer: Qualified fuel will not contain impurities and moisture when it leaves the factory, but dust, dirt and moisture will be mixed in more or less during transportation and storage. When the fuel tank is not full, the moisture in the air in the tank will easily form condensed water droplets and mix in. In fuel, the following points should be noted when using and storing fuel: 1) The fuel must be stored in the tank for more than 24 hours before use. Use after water and impurities have settled; 2) Try to fill the daily fuel tank after each work, so as to prevent the moisture in the air in the tank from mixing into the fuel; 3) Before filling the fuel, wipe the funnel and fuel tank end cap clean first. When using a hand pump, be careful not to pump out the lower sediments together; 4) Open the drain cock of the fuel tank regularly to remove accumulated water and sediment.
7. What kind of fault can cause the gear of the starter motor of the motor (electric ball) group to break?
Answer: The battery power is insufficient or the battery temperature is too high; the starter motor relay does not work; the starter motor transmission gear and the flywheel ring gear cannot mesh; the starter motor enters the mesh and the diesel engine cannot rotate or rotates weakly; the starter motor does not rotate; the startup fails; after the diesel engine is running It cannot be separated from the starter motor;
8. What is the main reason for AVR damage?
Answer: The AVR circuit consists of three parts: the rectifier main circuit, the voltage detection circuit, and the comparison control circuit; excluding the possibility of damage caused by the quality of the original electrical components themselves, in the entire AVR circuit, the main circuit and comparison circuit The operating frequency of the control circuit changes the most; among them, the rectifier bridge of the main circuit and the comparison circuit The transistor changes more frequently, and its damage ratio accounts for more than 90% of the damage rate of the entire AVR. Since the AVR on the imported generator is a non-repair accessory, if it is damaged, it must be replaced with a new one. Therefore, we mainly analyze the AVR on the generator caused by Cause of damage, it is most important to avoid damage to the AVR as much as possible, as long as it is used properly , can improve the service life of the AVR. The more stable the generator voltage is, the smaller the fluctuation frequency within the AVR; the smaller the switching action of the transistor in the comparison circuit, the smaller the chance of AVR damage; the output load is relatively stable, and the fluctuation frequency within the AVR is The smaller the value, the smaller the switching action of the transistor in the comparison circuit, and the AVR will be damaged. The smaller the probability; the more stable the diesel engine speed, the smaller the oscillation impact of changing current on the AVR; regular 'wandering' and overload, and the large difference between the three-phase loads are the main reasons for AVR damage; choose For generator sets with E, F, and C fuel systems, the use of AVR will be more reliable due to small frequency changes.
9. What is the so-called reverse power supply? What are the two serious consequences?
Answer: The situation in which self-provided generators (power balls) send power to the city grid is called reverse power supply. There are two serious consequences:
1) If there is no power outage in the city grid, the city grid power supply and the self-prepared generator power supply will be paralleled out of sync, which will destroy the unit. If the self-prepared generator capacity is large, it will also cause the city power grid to oscillate.
2) The municipal power grid has been out of power and is being inspected. If its own generator sends power backwards, the inspection personnel of the power supply department will be electrocuted.
10. Why can’t it be shut down and started up under load?
Answer: Shutdown under load is an emergency shutdown, which will have a greater impact on the unit. Starting up under load is an illegal operation and will cause damage to the electrical equipment of the power generation equipment.
11. What happens when the generator loses excitation and how to deal with it?
Answer: If the generator is not used for a long time, the residual magnetism contained in the iron core before leaving the factory is lost, and the excitation coil cannot establish the required magnetic field. At this time, the engine runs normally but cannot generate electricity. This phenomenon is new. Or There are many units that have not been used for a long time. Treatment methods:
1) If there is an excitation button, press the excitation button
2) If there is no excitation button, use a battery to magnetize it.
3) Load a light bulb and run it at overspeed for a few seconds
12. What is the load sequence after powering on?
Answer: Bring the load in order from large to small.
13. What is the sequence of unloading the machine?
Answer: The loads are removed in order from small to large, and finally shut down.
14. What happens when the generator (electric ball) loses magnetism, and how should it be dealt with?
Answer: If the generator (electric ball) is not used for a long time, the residual magnetism contained in the iron core before leaving the factory is lost, and the excitation coil cannot establish the proper magnetic field. At this time, the engine runs normally but cannot generate electricity. Such phenomena There are many new machines or units that have not been used for a long time. Treatment methods:
1) If there is an excitation button, press the excitation button
2) If there is no excitation button, use a battery to magnetize it.
3) Put a light bulb on load and run it at overspeed for a few seconds.
15. What is the so-called three-phase four-wire system?
Answer: There are 4 outlet wires of the generator set, 3 of which are live wires and 1 is neutral wire. The voltage between the live wire and the live wire is 380V. The voltage between the live wire and the neutral wire is 220V.
16. What is a three-phase short circuit? What are the consequences?
Answer: A direct short circuit without any load between the live wires is a three-phase short circuit. The consequences are very terrible, and in serious cases, it can lead to the destruction of the machine and death of people.