1. Closed-loop air cooling
For turbine generators under 50,000 kilowatts, a closed-loop air cooling system is often used and the engine fan is used to blow the heater. components to cool.
2. Hydrogen Cooling
For generators with a capacity of 50,000 to 600,000 kilowatts, hydrogen cooling is widely used. The heat dissipation performance of hydrogen (purity 99%) is better than that of air, and the heat dissipation effect is good, which can greatly reduce the ventilation friction loss of the motor, thereby greatly improving the efficiency of the generator. Explosion-proof and leak-proof measures must be taken when using hydrogen cooling, which makes the engine structure more complex and increases the consumption and cost of electrode materials.
3. Refcooling by liquid fluid
The relative cooling capacity of water is 50 times greater than that of air. To remove the same heat, the flow rate of water required is much lower than that of air. air. Therefore, using hollow wires in the coil and passing water through the wires for cooling can significantly reduce the temperature rise of the motor, delay insulation aging, and extend the service life of the engine.
Detailed information
Strictly treated hydrogen for cooling can ensure that the inside of the generator is clean, the ventilation and cooling effect heat dissipation is stable, and there will be no problems caused by dirt.
Hydrogen contains very little oxygen, less than 2%, and does not support combustion. Even if a short circuit fault occurs inside the generator, there is no risk of fire, whichui can significantly reduce the degree of combustion. Damage caused by fault. In hydrogen there is less noise and the insulating materials are less susceptible to oxidation and corona damage.
The hydrogen in the generator must maintain the specified purity to ensure the operating performance of the generator and avoid explosions. For this purpose, a hydrogen supply device must be installed.
References:
Main cooling methods and characteristics of large generators
The generator stator core is divided into 13 wind zones along the direction axial, 6 three of the air inlet zones and seven air outlet zones are arranged alternately. The air inlet areas and the air outlet areas are respectively connected to each other. There are a number of troRadial ventilation holes on the stator core. The cooling of the rotor winding adopts the "air gap" system: two rows of diagonal flow holes in different directions are drilled in the rotor bar to the bottom of the slot, forming several Parallel diagonal flow channels along the axial direction of the rotor body. Through these channels, the cooling hydrogen gas alternately enters and flows from the air duct of the air inlet of the rotor winding, forcing the cooling hydrogen gas to reach the bottom of the slot of the conductor through the oblique flow channel at a speed which corresponds to the speed of the rotor. , then turns to the other side along the same oblique flow path. The flow channel flows out of the conductor. The cold air blown from each air inlet is divided into two oblique flow channels and flows into the conductor inux directions. Likewise, there are two air outlet channels that merge and flow from the air outlet into the air gap. Therefore, each channel has a “V” shape seen from the longitudinal section of the parallel bar, and a “U” shape from the cross-sectional view of the vertical bar. Cooling air from the rotor winding enters and exits the air zone and. the stator core moves in and out.corresponding to the area.
A generator is a mechanical device that converts other forms of energy into electrical energy. It is driven by water turbine, steam turbine, diesel engine or other electric machines to convert the energy generated by water flow, air. flow, fuel combustion or atomic nuclear fission in Mechanical energy is transmitted to the generator, which is then converted into electrical energy. Generators are widely used in industrial and agricultural production, defense nnationality, science and technology and daily life.
Generators come in many forms, but their operating principles are all based on the law of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its construction is: using suitable magnetic and conductive materials to form magnetic circuits and circuits that conduct electromagnetic induction among themselves to generate electromagnetic energy and achieve the conversion goal of energy.
Operating characteristics:
The main characteristics that characterize the performance of synchronous generators are the no-load characteristics and the load operating characteristics.
These features provide an important basis for users to choose generators.
No-load characteristics:
When the generator is not connected to a load, the armature current is zero, which is called no-load operation. At this time, the three-phase winding of the motor stator only has the no-load electromotive force E0 (three-phase symmetry) induced by the excitation current If, and its size increases with the increase of If. However, due to the saturation phenomenon in the core of the motor's magnetic circuit, the two are not proportional. The curve reflecting the relationship between the no-load electromotive force E0 and the excitation current If is called the no-load characteristic of the synchronous generator.
Armature reaction:
When the generator is connected to a symmetrical load, the three-phase current in the armature winding will produce another rotating magnetic field, called magnetic reaction d 'induced. field. Its speed is exactly equal to the speed of the rotor and the two rotate synchronously.
The armature reaction magnetic field and the m fieldmagnetic excitation of the rotor of the synchronous generator can be approximately considered to be distributed according to the sinusoidal law. The spatial phase difference between them depends on the temporal phase difference between the no-load electromotive force E0 and the armature current I. The armature reaction magnetic field is also related to the charge state. When the generator load is inductive, the armature reaction magnetic field acts as a demagnetizer, which will cause the generator voltage to decrease; when the load is capacitive, the armature reaction magnetic field acts as a magnetizer, which will reduce the generator voltage; the generator output voltage increases.
Load operating characteristics:
Mainly refers to external characteristics and adjustment characteristics. The external characteristic is the relationship between the voltage across the generator U and the currentt of load I when the speed is the nominal value, the excitation current and the load power factor are constant. The setting characteristic is the relationship between the excitation current If and the load current I when the speed and terminal voltage are nominal values and the load power factor is constant.
The voltage change rate of the synchronous generator is about 20-40%. General industrial and household loads require the voltage to remain virtually unchanged. For this reason, as the load current increases, the excitation current must be adjusted accordingly. Although the change trend of the fitting characteristic is exactly opposite to that of the external characteristic, for inductive and purely resistive loads it increases, while for capacitive loads it generally decreases.
The forms of cooling of generatorsiesel are generally divided into three types: air, hydrogen and water. Generally, the cooling system of a synchronous generator is closed and the cooling fluid is used cyclically.
1) Air Cooling – Air cooling is done by fans. Cold air is blown against the ends of the diesel generator windings, the generator set stator and rotor to dissipate heat. absorbs heat. Then it turns into hot air. After the air between the stator and rotor is fused, it is discharged through the iron core air duct and cooled by the cooler. The cooled air is then sent into the generator by the fan to circulate there to achieve the heat dissipation goal. The machines generally use air cooling for medium and small synchronous generator sets. ,
2) Hydro coolinggene - Hydrogen cooling uses hydrogen as a cooling medium. The heat dissipation performance of hydrogen is better than that of air. Most large turbine generators use hydrogen cooling.
3) Water cooling - water cooling uses dual internal water cooling of the stator and rotor.