Pmsg

PMIG

1. Content

2. Introduction The  permanent magnet synchronous generator  called so because in this synchronous generator excitation is provided with the permanent magnet instead of the external excitation source. Its rotor is consists of the permanent that generates a field for excitation and replaces the external supply source for the generator. In most of generation power plants, the synchronous generator is used. In steam turbines, hydro turbines, and in gas turbines synchronous generator is used. Like other  generators ,  the physical structure of this generator is the same it also consists of the rotor which also comprises of the permanent magnet with the shaft connected with it. Like stator of other generators, this generator also has a stator that provides protection to internal structure from the exterior environment. In permanent synchronous generator, there is no need of the slip rings and carbon brushes, which make the machine less expensive, lightweight, and maintenance of the generator also decreases.

3. But in high rating generators, large size generators are used that make machines somewhat expensive and increases the price. The generator attached with the power electronic conversion circuitry can work on the less speed and so there is no need of the gearbox. The presence of gearboxes increases the price, energy losses, and cost of repairing the generator but without the gearbox price and weight of circuitry deceases but it also the best option for the offshore applications. With the direction of flux lines, the permanent synchronous generator is divided into three categories first one is the radial flux permanent magnet synchronous generator, the second one is the axial flux permanent magnet synchronous generator and the third one is the transverse flux permanent synchronous generator.

4. Permanent Magnet Technology The use of permanent magnets (PMs) in construction of electrical machines brings the following benefits: No electrical energy is absorbed by the field excitation system and thus there are no excitation losses which means substantial increase in the efficiency , Higher torque and/or output power per volume than when using electromagnetic excitation, Better dynamic performance than motors with electromagnetic excitation (higher magnetic flux density in the air gap), Simplification of construction and maintenance , Reduction of prices for some types of machines .

5. Applications of Permanent Synchronous Generator These are some applications of the permanent magnet synchronous generator. It used to provide the power for the excitation of the high rating synchronous generator. During the short circuit, these generators provide the power to the generator connected in the system to maintain the required voltage for the system. It also used in such power generation systems where wind turbines are used.

6. Permanent Magnet Classification Permanent Magnet Synchronous Machine (PMSG) Perma n ent Magnet Permanent Magnet Brushless Machine (BLDC)

7. Permanent Magnet Classification

8. Introduction PM Synchronous Machine are widely used in Wind mile generation Industrial servo-applications due to its high-performance characteristics. General characteristics Compact High efficiency (no excitation current) Smooth torque Low acoustic noise Fast dynamic response (both torque and speed) Expensive

9. Construction PMSM Stator Rotor Radial Flux & Axial Flux Inner Rotor & Outer Rotor Longitudinal & Transversal

10. Radial & Axial Rotor If the normal vector is perpendicular to axis, machine is called Radial. If the normal vector is parallel with the axis, the machine is called Axial. Radial Rotor Higher po w e r rating achie v ed by increasing the length of machine. Used in Ship propulsion Robotics Traction Wind systems

11. Radial & Axial Rotor Axial Rotor Smaller than Radial machine High torque density Used in Gearless elevator systems Rarely used in Traction Generation

12. Longitudinal & Transversal Rotor In transversal flux machines, the plane of flux path is perpendicular to the direction of rotor motion. Transversal flux machines can be adjusted independently current loading and the magnetic loading. Used in Applications with high torque density requirement. Free piston generators for hybrid vehicles. Ship propulsion and wind system.

13. Inner and Outer Rotor

14. Inner Rotor The interior-magnet rotor has radially magnetized and alternately poled magnets. Because the magnet pole area is smaller than the pole area at the rotor surface, the air gap flux density on open circuit is less than the flux density in the magnet. The magnet is very well protected against centrifugal forces. Such a design is recommended for high frequency high speed motors .

15. Outer Rotor The surface magnet motor can have magnets magnetized radially or sometimes circumferentially. An external high conductivity non-ferromagnetic cylinder is sometimes used. It protects the PMs against the demagnetizing action of armature reaction and centrifugal forces, provides an asynchronous starting torque, and acts as a damper. The magnet is very well protected against centrifugal forces. Such a design is recommended for high frequency high

16. PM Configuration PM (Perman e nt Magnet ) S u r f ace Magnet Inset Magnet Buried Magnet

17. Surface and Buried Magnet Surface Magnets Simple construction Small armature reaction flux Permanent magnets not protected against armature fields Eddy-current losses in permanent magnets Expensive damper Buried Magnets Relatively complicated construction High armature reaction flux Permanent magnets protected against armature fields No eddy-current losses in permanent magnets Less expensive damper

18. Permanent magnet B-H curve

19. Operating Principle In the permanent magnet synchronous generator, the magnetic field is obtained by using a permanent magnet, but not an electromagnet. The field flux remains constant in this case and the supply required to excite the field winding is not necessary and slip rings are not required. All the other things remain the same as normal synchronous generator. The EMF generated by a synchronous generator is given as follows

20. Equivalent Circuit – rotor side Voltage Equation of PM machine in rotor reference

21. Equivalent Circuit – rotor side Fig: PM equivalent for d-axis & q-axis

22. Equivalent Circuit – rotor side Flux Linkage equations The Flux Linkage can be generated field current

23. Vector Diagram Stator reference axis X-Y axis Rotor reference axis d-q axis