Hello, friends, I hope all of you are enjoying your life. In today’s tutorial, I am going to explain Permanent Magnet Synchronous Generator. The synchronous generator is such a device that transforms mechanical energy into the electrical energy delivered by the prime mover of the generator. It is also known as an alternator. It is called a synchronous generator because its rotation speed is equal to the rotating speed of the field at the stator of the generator called synchronous speed. In this generator, an external supply is provided to excite the generator which is the reverse of the induction generator. For excitation, the external dc source is connected to a synchronous generator.
In today’s post, we will have a look at another type of synchronous generator called a permanent magnet synchronous generator. In this generator, there is no need of a separate dc source for the excitation of the generator. We will describe the working principle, applications, advantages, disadvantages, and some other related parameters of this generator. So let’s get started with the Permanent Magnet Synchronous Generator.
Permanent Magnet Synchronous Generator
- 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 the stator of other generators, this generator also has a stator that provides protection to the internal structure from the exterior environment.
- In a permanent synchronous generator, there is no need of slip rings and carbon brushes, which makes the machine less expensive, and lightweight, and maintenance of the generator also decreases.
- But in high-rating generators, large-size generators are used to make machines somewhat expensive and increase the price.
- The generator attached to the power electronic conversion circuitry can work at 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 decreases it is also the best option for 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.
What is Synchronous Speed
- PMSG is called synchronous generators since the voltage produced frequency in the stator or armature calculated in the hertz is directly proportional to the rotation cycles of the rotor.
- The formula to find the synchronous speed is 120 (fe/P).
- In this equation, the fe is the frequency of the voltage induced at the stator.
- P is the no of a pole in the generator.
Working Principle of Permanent Magnet Synchronous Generator
- The working of the PMSG depends on the field produced by the permanent magnet attached at the rotor of the generator for the conversion of mechanical energy into electrical energy.
- Like synchronous generators in PMSG, there are two types of windings first one is the armature that is wound on the stator and the second one is the field winding that is wound on the rotor.
- At the stator of the generator 6 soils of copper, and windings are wound and fixed at their respective places.
- The rotor that has a permanent magnet is connected to the bearing rotating on the shaft. In this generator, there are 2 rotors first one is behind the stator and the second one is at the exterior side.
- Both of these are connected with each other through the long studs moving by the hole in the stator.
- The blades are also surfaced on these studs that connect the rotors with each other.
- These blades rotate the rotor for the production of electrical energy.
- In the given figure you can see the construction of the generator.
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 is also used in such power generation systems where wind turbines are used.
Advantages of Permanent Magnet Synchronous Generator
- High efficiency: PMSGs are effective and provide about ninety percent of larger efficiency. it is that they do not need excitation circuits since permanent magnets make magnetic filed in this generator
- Low noise and vibration: They are vibration free and provide the noise-free solution so they are best for applications where noise and vibration are need
- Compact size and lightweight: These generators are less weight and small size the other types
- Wide speed range: it can operate on different speed values that make them effective for different applications
- Reliable operation: Their operating life is longer and have reliable operation
Disadvantages of Permanent Magnet Synchronous Generator
- Higher initial cost: Its purchasing cost is higher than another generator
- Susceptibility to demagnetization: They are less efficient for high-temperature conditions and get demagnetized
- Limited availability: it is not commonly available like others so difficult to get these generators
- Poor voltage regulation: its output volts are not easily regulated that makes it difficult to handle the load
- Need for a controller: For voltage and frequency output regulation it needs controllers
- Sensitive to load changes: it can be sensitive to load changes that result in frequency vary. it can be an issue when constant frequency is needed
Permanent Magnet Synchronous Generator Vs Permanent Magnet Synchronous Motor
| Characteristic | Permanent Magnet Synchronous Generator (PMSG) | Permanent Magnet Synchronous Motor (PMSM) |
|---|---|---|
| Function | it transforms mechanical energy into electrical energy | it transformed electrical energy into mechanical energy |
| Power Output | Produces electrical power | Consumes electrical power |
| Excitation | Permanent magnets provide the excitation | Permanent magnets provide the excitation |
| Stator and Rotor Configuration | Similar to an induction generator | like a brushless DC motor |
| Control | Output voltage and frequency are controlled externally | Speed and torque are controlled by varying the input voltage and frequency |
| Applications | Wind turbines, hydroelectric power plants | Electric vehicles, industrial machinery |
| Power Factor Control | Usually requires external power factor correction | Can operate at a unity power factor |
| Regenerative Capability | Can’t regenerate power, requires an external power source | Can regenerate power during braking or deceleration |
| Efficiency | Higher efficiency at high-speed operation | Higher efficiency at rated speed operation |
| Cooling Requirements | it requires additional cooling systems | Cooling requirements are generally lower |
Construction of Permanent Magnet Generators
| Part | Description |
|---|---|
| Permanent magnets | it is the main part of the generator. They produce magnetic filed whcih induces current in winnings |
| Spinning axle | Axle which is mounted on permanent magnets is spun by a motor or other mechanical energy sources |
| Windings | Windgins are wounded about the spinning axle. The magnetic field of a permanent magnet induces a current in the windings |
| Slip rings | Slip rings connected the outer circuits with the windings of generators. it helps current fo getout from the generator through outer circuits |
| Brushes | Brushes are connected with slip rings. They carry current from windings to the circuit connected |
Permanent magnet generator vs alternator
| Feature | Permanent Magnet Generator | Alternator |
|---|---|---|
| Type of generator | AC | AC |
| Uses permanent magnets | Yes | No |
| Requires a DC excitation circuit | No | Yes |
| Slip rings and brushes | Yes | No |
| Efficiency | Higher | Lower |
| Weight | Lighter | Heavier |
| Size | Smaller | Larger |
| Cost | More expensive | Less expensive |
| Applications | Wind turbines, electric vehicles solar panels, | trucks, Cars, motorcycles, boats |
Related posts
Synchronous Generator Equivalent Circuit
Synchronous Generator Phasor Diagram
Synchronous Generator Power and Torque
Synchronous Generator Parameters
Synchronous Generator Operating Alone
Synchronous Generator Parallel Operation
Synchronous Generator parallel with Large Power system
Synchronous Generator Parallel with same Size Generator
Synchronous Generator Capability Curves
Synchronous Generator Transients
So friends that is the detailed post on the permanent magnet synchronous generator I try my level best to simplify this article for you and explained each and every parameter related to the generator. If you have any further queries about this post as in the comments. I will guide you further. See you in the next tutorial. Thanks for reading.
I like what you guys are usually up too. Such clever work and reporting! Keep up the superb works guys I’ve included you guys to blogroll.
Hello, Great to read your articles and discussions about Permanent Magnet Generators. Thank you for those.
I am an “inventor” with a multitude of practical and theoretical skills.
I am building a micro hydro water turbine in the hills to produce 3 – 5 Kw of electricity off grid.
The hydraulic system is in place and I have purchased a three phase 380v Permanent Magnet Alternator. The system is to run into purpose designed house heating system consisting of a 1.5kW heat pump and switched domestic heaters. These were to 240v. Single phase to be derived from rectified three phase to 380v DC into a 3 and 2 kw sine wave inverters. to 240v AC.
So I need controllers. to maintain the speed of PMA rotation to the given voltage output.
Then the challenge for the design. Resistive load present no real problem but the heat pump compressor will present on starting- loading issues particularly if in single phase.
So now I am thinking about using a three phase compressor. (A local refrigeration company are to construct a bespoke machine).
If I stay in three phase I will have less losses and the system should be the most resilient to the high milli second loading currents and not stress the sine wave inverter.
If I were to change generator to use a synchronous induction generator with AGC the output voltage and frequency would be automatically controlled and maintained.
But I already have the PMA (suitable for a wind turbine etc) which is classic in internal wiring configuration Star / Delta.
So thanks for reading the long introduction. So at last here is the real question.
Can this alternator be controlled with any kind of constructed AGC with feed back to maintain the frequency as well as the output voltage particularly in the miili-second compressor start up times.
I don’t think the speed variation controller that I will build to switch solid state relays to the resistive loads will react fast enough due to the flywheel effects of the hydraulic system.
I really welcome your advice if you can.
Many thanks.
Very interesting, I need a generator domestic use to provide dc generation supplying a battery pack holding a 20kw capacity via inverter. Where can I buy these ? Any different sizes?