What is a Permanent Magnet Generator

What is a permanent magnet generator? Permanent magnet generator refers to a power generation device that converts mechanical energy transformed by thermal energy into electrical energy.

Permanent magnet generator has the characteristics of small volume, low loss and high efficiency. Next, let's specifically understand the principle of permanent magnet generator and the advantages of permanent magnet generator.

 

Working principle of permanent magnet generator

As with the alternator, the mechanical energy of the prime mover is transformed into electrical energy output by using the electromagnetic induction principle of wire cutting magnetic line of force to induce electric potential. It is composed of stator and rotor. The stator is the armature that generates power, and the rotor is the magnetic pole. The stator is composed of armature iron core, evenly discharged three-phase winding, base and end cover.

 

The rotor is usually of hidden pole type, which is composed of excitation winding, iron core and shaft, retaining ring, central ring, etc. The excitation winding of the rotor is connected with DC current to produce a magnetic field close to sinusoidal distribution (called rotor magnetic field), and its effective excitation magnetic flux intersects with the stationary armature winding. When the rotor rotates, the rotor magnetic field rotates with it for one cycle. The magnetic line of force 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 synthesizes to produce a turning magnetic field with synchronous speed. The interaction between stator magnetic field and rotor magnetic field will produce braking torque. From the steam turbine / water turbine / gas turbine, the input mechanical torque overcomes the braking torque to do work.

 

The advantage permanent magnet generator

1. Simple structure and high reliability.

The permanent magnet generator eliminates the excitation winding, carbon brush and slip ring structure of the excitation generator. The structure of the whole machine is simple and avoids the easy burning and disconnection of the excitation winding. Whole machine structure is simple, which avoids the faults of excitation generator, excitation winding of excitation generator is easy to burn and break, carbon brush and slip ring are easy to wear, etc

2. It can significantly prolong the service life of battery and reduce battery maintenance. The main reason is that the permanent magnet generator adopts the switching rectifier voltage stabilizing mode, which has high voltage stabilizing accuracy and good charging effect.

3.High efficiency.

Permanent magnet generator is an energy-saving product. The permanent magnet rotor structure eliminates the excitation power required to generate the rotor magnetic field and the mechanical loss of friction between carbon brush and slip ring, which greatly improves the efficiency of permanent magnet generator. The average efficiency of ordinary excitation generator is only 45% to 55% in the speed range of 1500 rpm to 6000 rpm, while that of permanent magnet generator can be as high as 75% to 80%.

4.Self starting voltage regulator is adopted without external excitation power supply.

The generator can generate electricity as long as it rotates. When the battery is damaged, the vehicle charging system can still work normally as long as the engine is running. If the car has no battery, ignition operation can also be realized as long as you shake the handle or slide the car.

 

What are the three problems of permanent magnet generator?

1. Control problem

The permanent magnet generator can maintain its magnetic field without external energy, but it is also very difficult to adjust and control its magnetic field from the outside. These restrict the application range of permanent magnet generator. However, with the rapid development of control technology of power electronic devices such as MOSFET and IGBTT, permanent magnet generator only controls the motor output without magnetic field control. The design requires the combination of neodymium iron boron materials, power electronic devices and microcomputer control to make the permanent magnet generator run under new working conditions.

 

2.Irreversible demagnetization problem

If the design and use are improper, when the temperature of permanent magnet generator is too high or too low, under the action of armature reaction generated by impulse current, and under severe mechanical vibration, irreversible demagnetization, or loss of excitation, may occur, which will reduce the performance of the motor and even make it unusable.

 

3.Cost problem

Because the current price of rare earth permanent magnet materials is still relatively expensive, the cost of rare earth permanent magnet generator is generally higher than that of electric excitation generator, but this cost will be better compensated in the high performance and operation of the motor. In the future design, the performance and price will be compared according to the specific application occasions and requirements, and the structural innovation and design optimization will be carried out to reduce the manufacturing cost. It is undeniable that the cost price of the product under development is slightly higher than that of the current general generator, but we believe that with the further perfection of the product, the cost problem will be well solved.

After reading above information, Dingbo Power company believes that you have had a certain understanding of the permanent magnet generator. Now for diesel generator set, it also has equipped with permanent magnet generator according to its power capacity. If you are interested, welcome to contact us by email dingbo@dieselgeneratortech.com.