Judgement and analysis of inter-turn short circuit of the rotor of hydro-turbine generator:
Short-circuit of rotor inter-turn is one of the common faults of hydro-turbine generator, which is very harmful to the safe operation of the generator. There are two situations of inter-turn short circuit: one is that it occurs shortly after the generator is put into operation. When the generator is not loaded or the load is very light, an inter-turn short circuit occurs. The phenomenon is smoke coming out of the pit and insulation. The smell of burning. The other is an inter-turn short circuit that occurs after long-term operation of the generator. The reasons are multi-faceted, such as poor manufacturing process, poor operation and maintenance, metal shavings or dust falling on the stator winding, and inter-turn short circuit if it is not cleaned for a long time. , it is also possible that small animals such as rats crawl into the stator chamber and cause short circuit between turns.
For the first case, when an inter-turn short circuit occurs, due to a very light or no load, the changes in the stator voltage and current are not obvious (the power supply voltage is normal), but there is smoke in the pit, and there is The smell of burning insulation. Personnel on duty should measure and inspect the generator with voltage transformers, current transformers and instruments based on the load of the generator, whether there is smoke or smell in the pit, and whether the generator sound is abnormal, etc. Differential protection to remove faults. When conditions permit, two-in-one (overcurrent, undervoltage, and overvoltage) protection should also be used to remove faults. When conditions are not met, the generator's backup protection can clear the fault.
For the second case, when an inter-turn short circuit occurs, it is due to heavy load or full load. Stator voltage and current will change significantly. The stator current increases and the voltage decreases. At this time, the generator load should be reduced immediately, and the duty leader and electrical branch leader should be reported quickly. After asking for permission from the chief engineer, the leaders of the biotechnology department and the dispatching station, disconnect the excitation switch and derail the generator to shut down. When conditions permit, external inspection and measurement should be carried out as much as possible to accurately locate the fault point. For example, the current value and voltage change of the inter-turn short circuit can be measured, and the unbalanced magnetic pull force can be measured. When you are confident that the generator can continue to operate. Generators should be operated in parallel with the consent of the reporting leader. When the conditions are not met. The fault should be cleared by the generator's backup protection.
Open the engine cover of the gasoline generator parking air conditioner to see oil leakage. Check to see if there are any abnormal noises. 1. Learn to distinguish the abnormal noises that are reasonable noises
For car abnormal noises, it is difficult for ordinary car owners to distinguish which ones are faulty abnormal noises and which ones are reasonable abnormal noises. There is bound to be a difference between the sound of a model equipped with a turbocharged engine and the sound of a naturally aspirated engine; models equipped with an engine guard may also produce noise due to friction; some car owners may be affected by their own noise after contacting different cars. Lack of understanding of mechanical knowledge, mistaking reasonable abnormal noises for vehicle failure. Therefore, learn to identify abnormal car noises to avoid wasting time and energy.
2. How to identify car noise:
In actual work, due to limitations of working conditions, it is difficult to use special instruments to measure car noise. Judgment of sounds to describe and compare car sounds. For example, bearing dry frictionA "squeaking" sound is emitted, a "clicking" sound similar to a small hammer tapping on the cement floor is emitted by an excessively large valve clearance, etc.
1. Correctly distinguish between normal sounds and abnormal sounds.
When the car is working, the vibrations of various mechanisms will emit sounds of various natures, but the sound does not mean that the car is faulty. In order to avoid unnecessary disassembly, we must first distinguish between normal sounds and abnormal sounds. Normal sound. The engine and exhaust sounds of various system components, gear meshing noise, etc. are all normal sounds. Abnormal noises (abnormal noises) can be divided into slight noises, normal noises and malignant noises according to their impact on car performance. Slight noises, such as the flashing sound of high-voltage electric leakage, the slight loose sound of rolling bearings, etc., are generally small in volume, the degree of wear of the parts is not large, and there is no significant change for a long time. Such faults can still maintain the car without repair. of normal driving.
3. When diagnosing abnormal car noises, attention should be paid to creating good auscultation conditions and trying to eliminate interference from other noises so as not to affect the accuracy of judgment.
It is best to consciously amplify or reduce the sound, that is, use a screwdriver or other metal rod as a stethoscope to contact the sounding part to amplify the sound, or use a single cylinder to cut off the fire to reduce the sound. , to meet diagnostic needs. The auscultation site should be kept quiet to minimize human interference.
3. Below we list some common abnormal car noises that are easy to eliminate and simple identification and elimination methods.
1. There are abnormal noises in the car body
Symptom description: When driving and pressing the accelerator or braking, there are always some abnormal noises in certain parts of the car body. The sound is not loud and does not affect normal operation. Driving, but there is always a little worry that something is wrong.
Analysis of the problem: This problem usually occurs because the body stiffness is insufficient, causing the vehicle to deform while driving, the door and the frame rub or shake, or desoldering in some places causes friction between steel plates, etc. .
There are also some cars that have louder wind noise. To a certain extent, this is related to the shape of the car. In some cars, the body parts of some cars are not fixed well and may cause abnormal noise. Generally, tighten the screws. It can be solved.
Solution:
First check whether there are unfixed objects in the trunk or rear seats that are easy to roll and make sounds, and exclude some items that are not fixed well and make sounds. noise.
If you find that the friction between the doors and windows causes abnormal noises, you can stick tape on the doors and windows or put rubber on the friction parts. You may be able to reduce or eliminate the abnormal noises, but the result is only a temporary solution and not the root cause. If none of the above problems are found, you must go to a regular repair shop for inspection and troubleshooting.
2. There are abnormal noises in the engine
Symptom explanation: There is a higher possibility of abnormal noises in the engine compartment. Most people also judge that the abnormal noises are in the engine compartment based on the source of the sound. , usually a metallic screeching sound or a whistling noise.
Analysis of the problem: Abnormal noise coming from the engine compartment, there will be a harsh belt howling sound, this is usually due toCaused by the belt slipping; there will also be the sharp sound of dry friction of metal parts when the engine is running, which is usually the cause of damage to the bearings of the generator, water pump, and power steering pump; if it is the sound of air leakage when the engine is running, it may be the exhaust The result of a clogged system, leaking or broken vacuum line.
Solution: Abnormal engine noise indicates that the technical status of a certain mechanism of the engine has changed. It is mainly caused by excessive wear of some parts or improper assembly and adjustment. Some abnormal noises can predict the possibility of accidental damage to the engine. Therefore, when abnormal noises occur in the engine, they should be repaired in time to prevent the failure from expanding.
It should be reminded that if there is abnormal noise in the engine, the car owner will probably not be able to solve it by himself, and it is best to send it to the factory for maintenance.
3. There is an abnormal noise in the gearbox
Explanation of symptoms: If there is a "rustling" sound inside the gearbox while the car is driving, but it disappears after the clutch or accelerator is depressed, replace it. There will be a whistling sound when shifting.
Analysis of the problem: If the source of the noise encountered during driving is the gearbox, it may be caused by wear of the gearbox bearings or gears, or bearing spots. If the gearbox makes abnormal noises when shifting gears at high speeds, it may be that the gearbox oil contains metal powder, indicating excessive wear of components such as the brake belt clutch in the gearbox.
4. There are abnormal noises in the tires
Symptom description: The tires make rhythmic noises, and the faster the vehicle speed, the higher the frequency.
Analysis problem: When a car tire contacts the ground, it will produce various noises of different strengths and weaknesses depending on the type or unevenness of the road, the speed of the car, the type of tire, and the air pressure of the tire itself. Therefore, no matter how perfect a car is, it cannot completely eliminate the noise generated by the tires and the ground during driving.
5. The engine guard has abnormal noise
Explanation of symptoms: The engine guard has been installed for a while, but after going out for some suburban driving, there was a noise at the guard plate when I came back. Strange noise.
Solution: Screws tend to shift in cars that move frequently. If you often hear "pop, pop, pop" noises from the air intake grille, in addition to the grille really In addition to looseness, the car owner still needs to check whether the engine guard plate screws are loose, or the engine guard plate and the bottom plate are loose. If the abnormal noise is caused by looseness, in addition to tightening the screws, some cardboard items should also be placed at the abnormal sound area. Abnormal noise can be easily eliminated.
6. The brakes make abnormal noises
Symptom description: The vehicle makes relatively loud noises and abnormal noises when the brakes are applied.
Analysis of the problem: Of course, abnormal noise during braking may also be caused by other reasons, such as improper use or deformation of the material of the brake disc, the hardness, porosity, friction characteristics and The compression characteristics are unqualified, the brake pads and brake discs are damp and rusty, the metal wire in the brake pad formula is too hard, and mechanical brake pad scrapers are among the reasons. To solve this problem, you only need to brake vigorously several times in succession to eliminate the abnormal noise.
6. There is abnormal noise in the brakes
Symptom description: The vehicle makes relatively loud noises and abnormal sounds when the brakes are applied.
Analysis of the problem: Of course, abnormal noise during braking may also be caused by other reasons, such as improper use or deformation of the material of the brake disc, the hardness, porosity, friction characteristics and The compression characteristics are unqualified, the brake pads and brake discs are damp and rusty, the metal wire in the brake pad formula is too hard, and mechanical brake pad scrapers are among the reasons. To solve this problem, you only need to brake vigorously several times in succession to eliminate the abnormal noise.
Solution:
The brake pad is one of the most important parts in the braking system. Generally, the life of the front brake pad is 30,000 km, and the life of the rear brake pad is 30,000 km. The service life of dynamic friction plates is 120,000 km. If there is a "squeaking" sound when applying the brakes, it is most likely a warning sound from the wear indicator of the brake pad, which indicates that the brake pad has exceeded its usage limit. When this happens, car owners should go to the car dealership for maintenance as soon as possible, otherwise the brake pads will be exhausted, causing damage to the brake components, abnormal braking effect and accidents.