1. Generator overheating
(1) The generator does not operate according to the specified technical conditions. If the stator voltage is too high, the iron loss increases; the load current is too large, and the stator winding copper loss increases. ; The frequency is too low, which slows down the cooling fan speed and affects the heat dissipation of the generator; the power factor is too low, which increases the rotor excitation current and causes the rotor to heat up. Check whether the indication of the monitoring instrument is normal. If it is abnormal, necessary adjustments and treatments must be made to make the generator operate according to the specified technical conditions.
(2) The three-phase load current of the generator is unbalanced, and the overloaded one-phase winding will overheat; if the difference between the three-phase current exceeds 10% of the rated current, it is a serious phase current imbalance. Unbalanced three-phase current will produce a negative sequence magnetic field, thereby increasing losses and causing heating of components such as pole windings and ferrules. The three-phase load should be adjusted to keep the current of each phase as balanced as possible.
(3) The air duct is blocked by dust and the ventilation is poor, making it difficult for the generator to dissipate heat. The dust and grease in the air duct should be removed to make the air duct unobstructed.
(4) The inlet air temperature is too high or the inlet water temperature is too high, and the cooler is blocked. The inlet air or water temperature should be lowered to clear the blockage in the cooler. Before the fault is eliminated, the generator load should be limited to reduce the generator temperature.
(5) Too much or too little grease should be added to the bearing. Grease should be added according to regulations, usually 1/2~1/3 of the bearing chamber (the upper limit is used for low speed, and the upper limit is used for high speed). lower limit), and should not exceed 70% of the bearing chamber.
(6) Bearing wear. If the wear is not serious, the bearing may be overheated locally; if the wear is serious, the stator and the rotor may rub together, causing overheating of the stator and rotor avoidance parts. The bearings should be checked for noise. If friction between the stator and rotor is found, the machine should be stopped immediately for maintenance or bearing replacement.
(7) The insulation of the stator core is damaged, causing an inter-piece short circuit, causing the core to increase local eddy current loss and generate heat. In severe cases, the stator winding will be damaged. The machine should be shut down immediately for maintenance.
(8) The parallel wire of the stator winding is broken, causing the current of other wires to increase and generate heat. The machine should be shut down immediately for maintenance.
2. There is an abnormal voltage between the neutral line of the generator and the ground
(1) Under normal circumstances, the air under each magnetic pole is caused by the influence of high-order harmonics or manufacturing processes. A very low voltage occurs due to uneven gaps and unequal magnetic potential. If the voltage is one to several volts, there is no danger and no need to deal with it.
(2) The generator winding has a short circuit or poor insulation to the ground, causing the performance of the electrical equipment and generator to deteriorate and easily generate heat. It should be repaired in time to avoid the expansion of the accident.
(3) There is no voltage between the neutral line and the ground when there is no load, but voltage appears when there is a load. This is caused by the imbalance of the three phases. The three-phase load should be adjusted to make it basically balanced.
3. The generator current is too large
(1) The load is too large and the load should be reduced.
(2) If a phase short circuit or ground fault occurs in a transmission line, the line should be inspected and restored to normal after the fault is eliminated.
4. The generator terminal voltage is too high
(1) The grid voltage of the generator parallel to the power grid is too high. The voltage of the parallel generator should be reduced.
(2) The fault of the excitation device causes over-excitation, and the excitation device should be repaired in time.
5. Insufficient power
Due to insufficient compound excitation compensation of the voltage source of the excitation device, it cannot provide the excitation current required for the armature reaction, causing the generator terminal voltage to be lower than the grid voltage. If the rated reactive power does not exceed the rated reactive power, the following measures should be taken:
(1) Connect a three-phase voltage regulator between the generator and the excitation reactor to increase the generator terminal voltage and make the excitation device The magnetic potential gradually increases.
(2) Change the phase of the excitation device voltage magnetomotive force and the generator terminal voltage to increase the resultant total magnetomotive force. Thousands of ohms and 10W can be connected in parallel at both ends of each phase winding of the reactor. resistance.
(3) Reduce the resistance of the rheostat to increase the excitation current of the generator.
The difference between the maximum temperature of the generator winding and the generator inlet air temperature
When we encounter an excessive water temperature alarm, we should first slow down and then drive the car to the road Also, do not rush to shut down the engine, because if the water temperature is too high, the temperature of the piston, steel wall, cylinder, crankshaft, etc. will be too high, and the engine oil will become thinner and lose its lubrication effect. If the engine is turned off at this time, the machine parts will be in an expanded state and the gaps between the accessories will be very small. After the machine is shut down, some soft metal will fall off, and some may even cause the cylinder to stick.
So after you find that the pot is boiling, do not turn off the heat immediately, but keep it running at idle speed temporarily to try to cool down.
Do not pour cold water on the engine when cooling down. This may cause the engine block to burst due to sudden cooling. The correct way is: put on gloves, put a piece of folded wet cloth on the water tank cover, gently unscrew the water tank cover a small gap, wait for the water vapor to slowly discharge, and after the water tank pressure drops, add cold water or antifreeze.
It is caused by water pipe leakage and insufficient cooling water. If this happens, you can add distilled water or purified water for emergency use, and then perform repairs when convenient. Just be careful not to open the water tank cover when the car is hot to avoid being burned by the water vapor sprayed out under strong pressure from inside. If there is enough water, check the fan behind the water tank. When the water temperature is high, the fan should be running even after the flame is turned off.
If the fan does not move, first turn the fan blades to see if the fan motor is stuck. If it is normal, it can be turned easily. If there is no problem with the motor, check the fan fuse. This is one of the causes of frequent fan failures, especially in summer when power consumption is high.
The failure of the thermostat is also a common cause of high water temperature. Once it fails, the cooling water circulation will be cut off. When there is a significant temperature difference between the two thick glue pipes above and below the water tank, it is the thermostat. Damage requires removal and replacement, which is generally left to professionals.
If the water temperature is a little high when driving, you should pay attention to whether there is too much mud, lint or gravel on the surface of the water tank, which will cause the heat dissipation capacity of the water tank to decrease. It is best to clean it dry when washing the car.net. For older models, high water temperature may be caused by scale accumulation inside the water tank and engine, so you need to go to a professional shop to clean it.
Extended information:
In fact, the car "boiling" is completely avoidable, even in summer, as long as you pay attention to the maintenance of your car and pay attention to some car usage Small details can completely nip "boiling" in the bud.
First of all, car owners should perform seasonal maintenance in time when the seasons change, and check the cooling system frequently to keep the fans, radiators and other components sensitive. Before leaving the car every day, just in case, you can also check whether the water tank is short of water. If you find that there is a lack of water, you should fill it up in time. Car owners can also keep a bucket of water in the trunk for emergencies.
Secondly, don’t neglect cleaning the surface of the water tank. Because dust, lint, etc. on the surface of the water tank will also affect the heat dissipation of the water tank, which is most obvious when the temperature is high in summer. When parking, you can choose to park in the shade. When the engine water temperature is too high, you can park in the shade to cool down.
Again, remember to pay attention to the water temperature when driving long distances or for a long time. Pay attention to the indication reading of the water temperature meter at any time while driving. It is required that the maximum temperature cannot exceed 95°C. Once it exceeds, the car owner must be vigilant. In addition, if you find that the water temperature is too high, it is best to pull over and rest. In special circumstances, in order to enhance the convection of cooling air, the engine hood can also be lifted to facilitate ventilation and heat dissipation.
In addition, if you encounter a traffic jam and the weather is not unbearably hot, car owners should try to turn off the air conditioner. This can reduce the rate of water temperature rise and prevent "boiling".
References:
The rated inlet air temperature of the generator, what should be the outlet air temperature?
The difference between the maximum temperature of the generator winding and the generator inlet air temperature The value is warm and long. When the generator is operating normally, the voltage is allowed to vary within the rated voltage range. The maximum allowable voltage for continuous operation of the generator shall not exceed the rated value. The minimum operating voltage of the generator shall be determined based on the requirements for stable operation. The maximum temperature of the generator windings The temperature difference with the generator inlet air temperature is long.
The inlet air temperature is the ambient temperature; the outlet air temperature should not exceed 40°C.
According to international technical requirements, the operating ambient temperature of the generator is defined as 40°C. All designs and powers are based on this ambient temperature. For generators, the ambient temperature is the inlet air temperature of the generator. Since the generator works together with the diesel engineIn operation, the heat generated by the diesel engine will cause the temperature in the entire space to exceed 40°C.
The ambient temperature of the generator during actual operation should not exceed 40°C. If the actual ambient temperature exceeds 40°C, the generator should run at reduced power. For the ambient temperature, if it is lower than 40°C, the power of the generator can be greater than the rated power.
Extended information:
Generator usage requirements:
1. Check that the transmission parts of the internal combustion engine and the generator should be connected reliably, the wires of the output line should be well insulated, and all instruments should be complete and effective.
2. After starting, it should be run at low speed for 3-5 minutes. The operation can only be started after the temperature and oil pressure wheel are normal. There should be no abnormal noise when the generator is speeding up, the slip ring and the brushes on the commutator should be in good contact, and there should be no jumping or sparking.
3. Before stopping, you should first cut off the main switches of each power supply branch, gradually reduce the load, cut off the main power supply switch of the generator, and return the excitation rheostat to the maximum resistance position to reduce the voltage to the lowest value. Cut off the excitation switch and neutral point grounding switch to stop the internal combustion engine.
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