Diesel Generator Commons Faults & Solution

2. Which energy level for electricity & the characteristics of AC electricity?

Answer: Electricity is a secondary energy source, AC power is converted from mechanical energy, and DC power is converted from chemical energy. Characteristics of AC cannot be stored and used now.

3. Why the generator (electric ball) work bin has to be clean?

Answer: If a diesel engine sucks in dirty air, the power will be reduced; if the generator sucks in sand, dust and other debris, the insulation between the stator and rotor gaps will be damaged, and at worst will cause burnout.

4. What cause high water temperature alarm shutdown and even unusable?

Answers: 1) The water tank is leaking or not enough;
2) The water temperature sensor is faulty;
3) Too thick dirt on the water tank or too much oil on the heat sink;
4) The fan belt is too worn and the pressure is insufficient;
5) The water pump is worn out and the pump water is insufficient;
6) The opening angle of the thermostat is insufficient, and it is stuck;
7) The cylinder head gasket is damaged, and the water line communicates with the cylinder;
8) Excessive wear on cylinder liners and local water seepage;
9) The computer room ventilation does not meet the requirements;
10) The machine is overloaded.

5. Why does the diesel engine emit black smoke?

Answer: When the diesel engine is under high load, the exhaust easily emits black smoke. The process of black smoke formation is not fully understood. It is generally believed that when the load of a diesel engine is high, the fuel injected into the combustion chamber increases, the temperature of the combustion chamber is higher, and the diesel engine mixture is getting higher. uneven, causing insufficient air combustion in some areas of the combustion chamber, and the fuel will decompose and polymerize to form soot (carbon black) in conditions of high temperature and lack of oxygen. Soot is not pure carbon, but a kind of polymer, the main component of which is carbon (more than 85%), but also contains a small amount of oxygen, hydrogen and ash, and its composition varies with the load of the diesel engine. Passing black smoke through the filter to collect soot and observing under the electron microscope, it is seen that the diameter of the soot particles is about 0.05μm large. High temperature cracking reactions from combustion in diesel engines are unavoidable, especially in diesel engines with mixed combustion in space. The high temperature gas surrounds the liquid oil droplets, providing the most favorable conditions for the crack reaction. High-speed photography of the combustion process confirms that there will be a lot of black smoke near the top dead center, but in general carbon smoke can find air on subsequent combustion and burn completely, leaving the exhaust black smoke free. However, if there is not enough air in the cylinder and the mixing process is slow, the cylinder temperature drops due to expansion, and the carbon cannot be burned and aggregated into soot. The formation of soot will make combustion incomplete, the economy of the diesel engine will decrease, the exhaust temperature will rise, the exhaust will emit black smoke, the surface of the combustion chamber will scorch, and the load can no longer be raised. Carbon deposits can also cause problems like piston ring or piston noise, valve spasms, etc. Therefore, diesel engines are not allowed to work under long-term overload conditions.

6. Why is there water in the oil tank and how to prevent it?

Answer: Fuel that meets the requirements will not contain dirt and moisture when leaving the factory, but dust, dirt and moisture will more or less mix up during transportation and storage; when the fuel tank is not full, the moisture in the air in the tank will easily form water droplets which condense and mix into the fuel. Pay attention to the following points in the use and storage of fuel:
1) Fuel must be stored in the fuel tank for more than 24 hours to allow water and dirt to settle before use;
2) Fill the fuel tank daily as much as possible after each job, to prevent the moisture in the fuel tank air from mixing into the fuel;
3) When filling the oil, first clean the funnel and cap the end of the oil tank. When using the hand pump, be careful not to pull the bottom sediment out together;
4) Open the fuel tank drain valve regularly to remove water and settling.

7. What kind of fault can cause the motor (electric ball) group to start the motor drive gear to beat the accident?

Answer: insufficient battery power; battery temperature is too high; motor start relay does not work; start the motor transmission gear and the flywheel ring gear cannot fuse; the starter motor into the diesel engine cannot turn or rotate weakly; motor starting does not rotate; motor start does not rotate; start failure; after the diesel engine works and motor start cannot be separated;

8. What is the main reason for AVR damage?

Answer: The AVR circuit consists of three parts, namely the main rectifier circuit, the voltage detection circuit, and the comparator control circuit; in terms of eliminating possible damage caused by the quality of the original electrical components, throughout the AVR circuit, the main circuit and the ratio of the operating frequency of the control circuit fluctuates the most; the rectifier bridge of the main circuit and the transistor in the comparison circuit fluctuate more frequently, and the damage ratio accounts for more than 90% of the damage rate of the entire AVR. Given that the AVR on imported generators is an accessory that cannot be removed, if it is damaged it must be replaced. Therefore, we mainly analyze the causes of damage to the AVR in the generator. The most important thing is to avoid damaging the AVR as much as possible, as long as it is used properly the service life of the AVR can be increased. The more stable the generator voltage is, the smaller the frequency of AVR changes; the smaller the switching action of the transistor in the comparison circuit, the less likely it is to damage the AVR; the output load is relatively stable, the smaller the frequency of the AVR changes, the transistor in the series of comparison. The smaller the switching action, the less likely the AVR will be damaged; the more stable the speed of the diesel engine, the less the impact of the vibration of changing currents on the AVR; the more it “runs” and is overloaded, the three-phase load difference is too large to cause AVR damage. The main reason for this: Choose a generator with E, F, C fuel system, because the frequency change is small, the use of the AVR will be more reliable.

9. What are the conditions for two generating sets to be parallel? What device is used to complete the parallel work?

Answer: The conditions for parallel use are the instantaneous voltage, frequency and phase of both machines. Commonly known as “three at a time”. Use special parallel devices to complete parallel work. It is generally recommended to use fully automatic cabinets. Try not to use manual parallel. Because manual parallel success or failure depends on human experience. With more than 20 years of experience in electric power work, the author boldly states that the reliable success rate of a manual parallel diesel generator is equal to zero. Never use the manual parallel concept for a large electric power system to implement a small power supply system, as the levels of protection of the two are completely different.

10. Why should all electrical contact parts be tightened after every 200 hours of operation?

Answer: Diesel generator set is a vibrating working device. In addition, many domestically manufactured or assembled units have to use useless double nuts. The use of spring washers is useless. After the electric fasteners are loosened, a large contact resistance will be generated and the unit will not operate normally.

11. How to match UPS power and diesel generator to ensure stable UPS output?

Answer: 1) UPS is generally expressed in KVA of apparent power, first multiply by 0.8 and convert to KW units consistent with the active power of the generator.
2) If a general generator is used, the UPS active power is multiplied by 2 to determine the generator power, that is, the generator power is twice the UPS power.
3) If a generator with PMG (permanent magnet engine excitation) is used, the UPS power is multiplied by 1.2 to determine the generator power, that is, the generator power is 1.2 times the UPS power.

12. Generator frequency and voltage are both unstable. Are the problem lies in the engine or generator?

Answer: It lies in the engine.

13. The generator frequency is stable, but the voltage is unstable. Are the problem lies in the engine or the generator?

Answer: It lies in the generator

14. What is the loss of magnetism of the generator and how should it be handled?

Answer: The generator has not been used for a long time, causing the residue contained in the iron core to disappear before leaving the factory, and the excitation coil cannot build up a proper magnetic field. Currently, the engine is running normally but is not there. electricity generated This kind of phenomenon is a new machine. Or there are more units that haven’t been used for a long time. Approach:
1) If the unit is equipped with an excitation button, press the excitation button once
2) If there is no excitation button, use a battery to pull it out;
3) Bring the light bulb load and run at speed for a few seconds.

15. What is the order of bringing the load after power on and off?

Answer: The loads are brought in order from largest to smallest.

16. What is the order of unloading before the machine?

Answer: The load is unloaded in order from small to large and finally shut down.

17. Why can’t I shut down and turn on the machine with load?

Answer: Shutdown with load is an emergency stop which has a large impact on the unit. Turning on the machine with load is a violation of the operation of power generation equipment and power equipment will bring damage.

18. The so-called three-phase four-wire system is how the matter?

Answer: There are 4 wires coming out of the generator set. 3 of which are the firewire and 1 of which is the zero wire. The voltage between the firewire and the firewire is 380 V. The voltage between the firewire and the zero wire is 220V.

19. What is the three-phase short circuit? What will be the consequences?

Answer: A direct short circuit between the firewire without passing any load is a three-phase short circuit. The consequences are very terrible, serious will lead to machine destruction.

20. What is the so-called reverse power supply? What are the two serious consequences?

Answer: The situation of a self-supplied generator (electric ball) sending power to the city grid is called reverse power transmission. There are two serious consequences:
a) If there is no power failure in the city network, the city grid power supply and the power supply from the self-supplied generator will produce asynchronous parallel operation, which will destroy the unit. If the self-supplied generator is of large capacity, it will also cause shocks to the city grid. b) The town grid is down and is undergoing maintenance, and the self-supplied generator is sending reverse power. This will cause electric shock to maintenance personnel in the power supply department.