1. Introduction to Permanent Magnet Generator
Permanent magnet generator (PMG) is a type of generator that is increasingly used in wind power generation. It has the advantages of high efficiency, low noise, simple structure and easy maintenance. PMG consists of stator, rotor, frame, end cover, cooling system and other components.
2. Working principle of PMG
The permanent magnet synchronous generator (PMG) in wind turbine is a common type of generator, and its working principle involves permanent magnet materials and electromagnetic induction. The following is the main working principle of wind power PMG:
Permanent magnet material: PMG uses permanent magnet material, usually rare earth permanent magnets, such as neodymium iron boron (NdFeB) magnets. These permanent magnet materials have a strong magnetic field and can generate a continuous magnetic field without an external power supply.
Stator and rotor: PMG also consists of two main parts: stator and rotor. The stator is the stationary part, which contains the winding, while the rotor is the rotating part, which is equipped with permanent magnets. When the rotor rotates, the magnetic field of the permanent magnet changes relative to the stator winding, causing electromagnetic induction.
Electromagnetic induction: Through the principle of electromagnetic induction, when the magnetic field of the permanent magnet changes relative to the stator winding, an AC voltage is generated in the stator winding. This is based on the principle of Faraday’s law of electromagnetic induction, that is, a changing magnetic field will induce an electromotive force.
Power generation output: The AC voltage generated in the stator winding is the power generation output of the PMG. The frequency of this AC voltage is related to the rotation speed of the rotor, while its amplitude is affected by the strength and rotation speed of the permanent magnet.
Power regulation: The output voltage and frequency of the PMG usually need to be adjusted to match the grid requirements. To achieve this regulation, a power electronic converter can be used, which converts the AC generated by the PMG into a current that adapts to the grid.
High efficiency: Since the PMG uses permanent magnets to generate a magnetic field, it can generate effective electrical energy at a lower speed than traditional induction generators, which improves the efficiency of the entire wind turbine.
In general, wind power PMG uses permanent magnet materials and electromagnetic induction principles to achieve an efficient process of converting wind energy into electrical energy. Its simple structure and high efficiency make it widely used in the field of wind power.
3. PMG structure composition
Stator: The stator consists of an iron core, windings and slots. The stator winding is directly connected to the power grid to generate a stator magnetic field.
Rotor: The rotor consists of permanent magnets, an iron core and a supporting structure. The permanent magnets generate a magnetic field, which interacts with the stator magnetic field to generate electromagnetic torque.
Frame: The frame is used to support the stator and rotor.
End cover: The end cover is used to seal the frame to prevent dust and dirt from entering the generator.
Cooling system: The cooling system is used to cool the heat inside the generator.
4. PMG operation characteristics
High efficiency: The efficiency of PMG is 2-3 percentage points higher than that of asynchronous generators.
Low noise: The noise of PMG is 5-10 dB lower than that of asynchronous generators.
Simple structure: The structure of PMG is simpler than that of asynchronous generators and is easy to maintain.
No excitation loss: PMG does not require an excitation system, so there is no excitation loss.
5. Common PMG fault phenomena
Common PMG fault phenomena include:
- Generator overheating
- Bearing vibration
- Voltage fluctuation
- Power output reduction
- Winding inter-turn short circuit
- Open circuit
- Permanent magnet demagnetization
6. PMG fault inspection and repair methods
1. Generator overheating
- Check whether the cooling system is working properly, including cooling fans, cooling water pumps, cooling pipes, etc.
- Check whether the air duct is unobstructed and whether there is any foreign matter blocking it.
- Clean the dust and dirt inside the generator.
2. Bearing vibration
- Check whether the bearing is damaged, including bearing clearance, bearing wear, etc.
- Check whether the lubricating oil is sufficient and ensure that the lubricating oil quality meets the requirements.
- Replace damaged bearings.
3. Voltage fluctuation
- Check whether the converter is working properly, including converter parameter settings, converter component damage, etc.
- Check whether the power grid is stable, including power grid voltage, power grid frequency, etc.
- Adjust the converter parameters to match the power grid.
4. Power output decrease
- Check whether the wind power is sufficient and eliminate the power output decrease caused by insufficient wind power.
- Check whether the generator is overheated and eliminate the power output decrease caused by overheating.
- Check whether the rotor winding is damaged, including short circuit between winding turns, winding open circuit, etc.
5. Short circuit between winding turns
- Use a megohmmeter to measure the insulation resistance of the winding to determine whether the winding has a short circuit between turns.
- Use a turn-to-turn short circuit tester to test and further confirm the location of the short circuit between turns.
- Replace the damaged winding.
6. Open circuit
- Check whether the connection of the winding is firm, including the winding joint, winding terminal, etc.
- Use a megohmmeter to measure the insulation resistance of the winding to determine whether the winding has a short circuit fault.
- Replace the open circuit winding.
7. Demagnetization of permanent magnets
- Check whether the temperature of the permanent magnet is too high, and take measures to reduce the temperature of the permanent magnet.
- Check whether the permanent magnet is corroded, and take measures to prevent corrosion of the permanent magnet.
- Replace the demagnetized permanent magnet.
Here are some additional suggestions to help you better operate and maintain your PMG:
- Inspect and maintain your PMG regularly
- Use professional tools and instruments to diagnose faults
- Strictly follow safe operating procedures
- Attend professional training courses