alternator

Power generation device

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Electric energy is one of the most important energy sources in modern society. alternator It is a mechanical equipment that converts other forms of energy into electrical energy. It is driven by a water turbine, steam turbine, diesel engine or other power machinery, and converts the energy generated by water flow, air flow, fuel combustion or nuclear fission into mechanical energy and then transfers it to a generator, which then converts it into electrical energy. Generators are widely used in industrial and agricultural production, national defense, science and technology and daily life.

Chinese name: alternator
Foreign name: alternating-current generator

Classification: Single phase, three-phase
Energy supply: Coal, oil, wind energy, water power, etc
Mode: Conversion of mechanical energy into electrical energy

catalog

Generator Set

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First, the concept of generator set: generator set refers to the generating equipment that can convert mechanical energy or other renewable energy into electrical energy.

Generally, our common generator sets are usually driven by steam turbines, water turbines or internal combustion engines (gasoline engines, diesel engines and other generators), wind energy, solar energy, biomass energy, ocean energy, etc. Diesel generator The largest market is mainly due to the large capacity of diesel generator sets, which can operate in parallel and have a long continuous power supply time, and can also operate independently. They do not operate in parallel with the regional power grid, and are not affected by power grid failures, with high reliability. Especially when the commonly used municipal power supply in some areas is not very reliable, the diesel generator can be used as the standby power supply, which can not only play the role of emergency power supply, but also can use some important loads during power failure through the reasonable optimization of low-voltage system. Therefore, it is widely used in engineering.

classification

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There are many forms of generators, but their working principles are based on Law of electromagnetic induction and Law of electromagnetic force 。 Therefore, the general principle of its structure is to use appropriate magnetic and conductive materials to form a magnetic circuit and circuit for mutual electromagnetic induction to generate Electromagnetic power To achieve the purpose of energy conversion.

The classification of generators can be summarized as follows:

alternator DC generator , Alternator Synchronous generator 、 Asynchronous generator (rarely used)

Alternators can also be divided into Single phase generator And Three phase generator 。

structure

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The generator is usually composed of stator 、 rotor , end cover, bearing and other components.

The stator is composed of stator core, wire wrapped winding, frame and other structural parts that fix these parts. The function of the stator is to generate alternating current.

The rotor is composed of rotor core (or magnetic pole, magnetic choke) winding, retaining ring, center ring, slip ring, fan, shaft and other parts. The function of the rotor is to generate a magnetic field. Installed inside the stator.

The principle is that the stator and rotor of the generator are connected and assembled by the bearing and end cover, so that the rotor can rotate in the stator to cut the magnetic line of force, so as to generate induced potential, which is led out through the terminal, connected to the circuit, and then generates current.

principle

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The mechanical energy of the prime mover is converted into electrical energy output by using the electromagnetic induction principle of the electric potential induced by the cutting magnetic force line of the wire. Synchronous generator It is composed of stator and rotor. The stator is the armature that generates electricity, and the rotor is the magnetic pole. The stator is composed of armature iron core, evenly arranged three-phase winding, base and end cover. The rotor is usually of non salient pole type and consists of excitation winding, iron core and shaft, retaining ring, central ring, etc. The excitation winding of the rotor is connected with DC current to generate a magnetic field close to the sinusoidal distribution (called rotor magnetic field), and its effective excitation flux is less than that of the static Armature winding Intersecting chains. When the rotor rotates, the rotor magnetic field rotates along with it, one cycle per revolution. The magnetic force line cuts each phase winding of the stator in sequence, and three-phase AC potential is induced in the three-phase stator winding. When the generator operates with symmetrical load, the three-phase armature current will generate a rotating magnetic field with synchronous speed. The interaction of stator magnetic field and rotor magnetic field will produce braking torque. From turbine/turbine/ gas turbine The input mechanical torque overcomes the braking torque and works.

install

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Electric starting Diesel generator set Step: check whether the electric shock contact of starting motor and electromagnetic control mechanism is good. Check whether the power wire is correct. Check whether there is dirt or oxidation on the battery terminal, and polish it clean. First, check whether the specific gravity of starting battery electrolyte is within 1.240~1.280. If the specific gravity is less than 1.180, it indicates that the battery is insufficient.

The installation and inspection steps of the alternator are as follows:

When installing the generator, ensure that the inlet of cooling air is unobstructed, and prevent the discharged hot air from entering the generator again. If there are louvers on the ventilation cover, the windows should face down to meet the requirements of the protection level. For mechanical coupling of single bearing generator, pay special attention to the uniform air gap between stator and rotor.

Alternator and Diesel generator Coupling, the parallelism and concentricity of the coupling are required to be less than 0.05mm. In actual use, the requirements can be slightly lower, about 0.1mm. If it is too large, it will affect the normal operation of the bearing, resulting in damage. When the coupling is good, it should be fixed with a locating pin. Re measure the coupling before installation.

There are U, V, W and N marks on the terminal in the generator outlet box, which does not mean that the actual phase sequence depends on the rotation direction. The certificate is printed with UVW indicating the actual phase sequence when rotating clockwise, and VUW indicating the actual phase sequence when rotating counterclockwise.

sliding bearing During the coupling of the generator, the height of the generator center should be adjusted slightly to the center of the diesel engine, so that the weight of the flywheel on the diesel engine will not be transferred to the generator bearing, otherwise the generator bearing will bear the weight of the flywheel, which is not conducive to the formation of the oil film of the sliding bearing, causing heat, or even burning the bearing. The coupling of this type of generator shall not carry any heavy objects.

If the neutral points of each generator in the power supply system are connected with each other, or the neutral point of the generator is connected with the neutral point of the transformer and its load, the neutral line current of three times the frequency will be outgoing from the neutral line during the operation of the unit. Therefore, it is necessary to measure the neutral current of the generator under various load conditions that may occur during operation. In order to prevent the generator from overheating during operation, the line current shall not exceed 50% of the rated current of the generator. If the neutral line power is too large, the neutral line reactor shall be installed on the neutral line to limit it.

Select appropriate power cables according to the schematic diagram or wiring diagram, and use copper connectors for wiring. After the copper connectors are fastened to the bus bars, the local clearance at the joints is not more than 0.05mm, and the distance between the conductors is not more than 10mm. Necessary grounding wires are also required.

Usage specification

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(1) The ground polarity of the battery must be the same as that of the alternator. If the diode is not used according to the specification, the diode will be damaged due to high current discharge.

(2) When the six diodes of the rectifier tube are connected to the stator winding, it is absolutely prohibited to use a megger or 220V AC power supply to check the insulation of the alternator. Otherwise, the diode may be damaged due to breakdown.

(3) Turn off the ignition switch after the engine is stopped. If the ignition is not stopped in time, the battery will continue to discharge, which will affect the magnetic field and shorten the service time of the battery.

(4) When the alternator is running, the fire test method cannot be used to check whether it is generating electricity. Otherwise, diodes and electronic components may be easily damaged.

(5) The grounding form of the regulator and the alternator must be the same, otherwise the alternator will be unable to output voltage due to no field current. And their voltage levels should be the same, otherwise the charging system can not work normally.

(6) If the alternator does not generate electricity or the charging current is small, the fault shall be eliminated in time, and the wire connection between the alternator and the battery shall be firm. Otherwise, it is easy to damage diodes and electronic components.

(7) When the alternator is installed on the engine, the center of the pulley groove of the alternator shall be aligned with the center of the pulley groove of the engine, and appropriate V-belt tightness shall also be set.

(8) When installing the V-belt early, pry the front cover of the alternator. Otherwise, pressure loss elements will occur^[1] 。

operation

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step

1、 Preparatory work

Disconnect the high-voltage switch in the distribution room and turn the disconnector to the power generation position.

1. Close the isolating switch of the generator room to the generating position.

2. Check the generator's cooling water The storage of lubricating oil and fuel oil shall be replenished in time in case of any shortage.

3. Check whether the connecting parts, fasteners and control parts are loose, fall off and stuck. Whether the wire connections are firm, correct and in good contact.

4. Open the control cabinet under the generator operation screen, close the startup switch switch, and wait until the display screen is powered on. Press the up and down page turning key to check the relevant operation records of the generator. If any abnormality is found, it shall be handled immediately and be ready for power generation.

2、 Start operation

1. Press the start button to start the generator. At the same time, pay attention to whether there is mechanical noise, abnormal vibration, etc.

2. During operation, the operator closely monitors through the instrument Generator Set Voltage, frequency, current, power factor, oil temperature, oil pressure, water temperature, charging current, speed and other instrument indications and changes. When the specified value is exceeded, check and take measures in time, and continue to operate after recovery.

3. The emergency stop button on the control panel is only used in case of emergency. After pressing the button, the generator will stop immediately, and an audible and visual alarm will be sent.

4. After the standby generator operates normally, close the main switch of the generator set (low-voltage air switch), and the generator supplies power to the electrical load.

3、 Shutdown

1. After the mains power is normal, gradually cut off the load and disconnect the main switch of generator set (low-voltage air switch).

2. Gradually reduce the speed to idle speed under no-load condition, and stop the engine when the temperature of water and oil of the diesel engine drops below 70 ℃.

3. Disconnect the startup control power supply, and close the isolation switch to the mains position according to the operation sequence.

mode

Manual operation

（1） Check before startup:

1. Turn on the power.

2. Check whether the following items are normal:

(1) Water level of water tank

(2) Oil and diesel oil level

(3) Battery voltage

(4) Battery water level

3. Check the control panel, switch the main switch to the stop position, close the detection switch, open the detection switch after the display is normal, all instruments should display zero, and the indicator light should display shutdown.

（2） Start up

1. Switch the main switch to the manual start position, the generator should start immediately, and the indicator light displays normally.

2. Observe the various instruments on the control panel, which shall operate normally.

3. If it is necessary to operate with load, close the power output switch.

（3） Shutdown

1. Cut off the rear end load first and then turn off the power output switch.

2. After five minutes of no-load operation, switch the main switch to the stop position.

3. After checking that everything is normal, switch the main switch to the automatic start position and close the power output switch.

Automatic operation

（1） Please refer to manual operation for inspection before startup, but after inspection, switch the generator to the automatic startup state and close the power output switch.

（2） Start up: cut off Taidian Power supply, observe whether it starts automatically.

（3） Shutdown: turn on the power supply of the Taiwan Electric Power and observe whether the power supply is automatically switched and Automatic shutdown 。

3、 Emergency shutdown

（1） In case of emergency, if the protection device of the generator refuses to start, the generator shall be shut down in an emergency and the main switch shall be switched to the off position.

（2） After emergency shutdown, the generator shall be fully checked immediately, and it shall be restored to normal operation as soon as possible.

Note:

1. The no-load operation of the generator shall not exceed 15 minutes.

2. After the generator starts and runs, check the water level, engine oil level, diesel oil level, battery voltage and battery liquid of the generator to keep them in normal condition.

3. Operation records shall be made for each detection or automatic startup.

maintain

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Normal maintenance

The no-load test run shall be conducted once a week for 10-15 minutes, so as to find problems in time and ensure that the battery has enough capacity for the generator to start.

1. Turn off the generator before maintenance Automatic air switch , set the main switch to the stop position, and disconnect the positive and negative stages of the battery power cord Confirm that the generator cannot be started.

2. Check the battery electrolyte If the water level is insufficient, add sulfuric acid solution or distilled water 。

3. Calculate the cumulative running time of the generator from the last maintenance. The air filter should be cleaned every 50 hours. The oil filter, diesel filter Water filter Replace the filter element every 250 hours.

4. Check the unit for water and oil leakage, and clean the generator body.

5. Connect the battery power cord and connector, and the test fault indicator should be all on.

6. Check whether the grounding wire is in good condition.

7. Check the machine room air ejector fan Operation condition, and whether the diesel oil quantity is enough to run for eight hours.

8. Check whether the cold water level and oil level are normal.

9. After the manual test run is normal, turn on the generator Automatic air switch , the main switch is switched to the automatic start position, the simulated power failure test is conducted, and the automatic start condition of the generator is observed.

10. Operate the generator with load for one hour, and observe whether the instrument indication and unit operation are normal.

11. Fill in operation records and maintenance records·

Technical maintenance

Diesel generator set According to the usage, it can be divided into two types: one is based on mains power, with generator set as standby power supply equipment, and the other is based on generator as main power supply equipment. The service time of the generators in the two cases is quite different. The maintenance of diesel generators is generally determined by the accumulated hours of startup. The first power supply mode mentioned above only has a few hours of commissioning every month. If the technical maintenance is carried out after the second and third technical maintenance hours are accumulated, the time will be too long. Therefore, it should be flexible to grasp the specific situation and carry out technical maintenance in a timely manner, It can eliminate the undesirable phenomenon of the machine as soon as possible, ensure that the unit is in good condition, and extend the service life of the machine. Therefore, to make the diesel engine work normally and reliably, the technical maintenance system of the diesel engine must be implemented. The technical maintenance categories are:

1、 First level maintenance inspection (daily or weekly)

2、 Level II maintenance inspection (every 250 hours or one month)

3、 Level III maintenance inspection (every 1500 hours or half a year)

Notes: 1. Application of "three-level maintenance", "medium maintenance" and "overhaul maintenance" Diesel generator Professional maintenance company completed.

2. The standby generator shall regularly start the diesel generator set to run for about 10 minutes to evaporate the water in the diesel engine to prevent moisture and corrosion.

（1） First level maintenance and inspection

<1> Check the oil level

Check the oil level with the oil dipstick of the diesel engine. In order to obtain accurate readings, the engine oil level should be stopped for 15 minutes, and checked when the engine oil flows back to the oil pan. The engine oil level should be matched with the original oil pan, and the engine oil level should be kept as close as possible to the high "H" mark.

Warning: Never operate the diesel engine when the oil mark is lower than the low mark "L" or higher than the high mark "H" (if necessary, add oil with the same quality and brand in the diesel engine).

<2> Check the cooling system

Keep the coolant full to the working plane. Check the coolant level every day or every time before starting the machine, analyze the reasons for coolant consumption, and check the coolant level only after the cooling system has cooled.

<3> Check the connections of the intake pipe

Check each connection of the air inlet pipe for looseness of the clamp, crack, perforation or wear of the hose, breakage or other damage of the hose, tighten the clamp or replace the parts as required to ensure that the air inlet system is well sealed and that all air passes through the air filter.

<4> Appearance inspection

Check whether there is external air leakage, coolant or oil leakage. Tighten screw connections, joints, etc. or replace gaskets as required. Check the oil filler pipe covers of the oil dipstick for tightness.

<5> Check for damage

inspect fuel system Including the wrong investigation or damage of the fuel pump, and check all connections for leakage or damage.

<6> Check the drive belt

Visually check whether the belt of fan, water pump and charger is damaged or loose, and replace it if the buckle is damaged. Adjust the tightness, and ask professional technicians to adjust if necessary.

<7> Precautions during maintenance

1. The lubricating oil pressure is low.

2. Insufficient power.

3. The coolant or oil temperature is too high.

4. Excessive consumption of coolant, oil and fuel.

5. The engine sound is abnormal, the smoke color is abnormal, and the smoke exhaust pipe is red.

<8> Precautions when using false load

1. The loading process is 25%, 50%, 75% and 100%.

2. Revise the actual power used.

3. Run with full load for one hour.