Permanent Magnet Materials
Permanent magnet motors use Permanent Magnet Materials to generate the motor’s magnetic field and do not require excitation coils or excitation current. Compared with traditional electric excitation motors, they have significant advantages such as high efficiency and simple structure.
The application range of permanent magnet motors is extremely wide, covering almost all fields of aerospace, national defense, industrial and agricultural production, and daily life. With the development of high-performance permanent magnet materials and the rapid development of control technology, the application of permanent magnet motors will become More extensive. Today, I will take you to understand the impact of permanent magnet motors and permanent magnet material properties on motors.
Principle and structure of Permanent Magnet Materials motor
Everyone knows that there are many types of motors, but the basic principles are to use electromagnetic and electromagnetic induction phenomena to realize the mutual conversion of electrical energy and kinetic energy Permanent Magnet Materials. If you want to know more about the basic principles and structure of motors, you can click to view the basic principles and basics of motors. structure. Today we take permanent magnet DC motors and permanent magnet synchronous motors as examples to give you a brief introduction to Permanent Magnet Materials motors.
1. Permanent magnet DC motor
The working principle and structure of the Permanent Magnet Materials DC motor are similar to those of ordinary DC motors, except that Permanent Magnet Materials poles are used instead of current-excited magnetic poles. They can be divided into brushed motors and brushless motors based on different commutation methods. The former is mechanically commutated, and the latter is or electronic commutation.
Taking a DC brush motor as an example, the Permanent Magnet Materials poles are arranged on the same circle, and the blue magnetic lines represent the magnetic circuit of the motor.
The rotor of a Permanent Magnet Materials brushed DC motor is composed of a rotor core, a rotor winding, a commutator, and a rotating shaft, which is the same as the rotor of an ordinary DC motor. Insert the rotor and brush assembly into the stator to form a Permanent Magnet Materials DC motor.
Small and medium-power permanent magnet DC motors are widely used in electric bicycles, electric motorcycles, and scooters.
2. Permanent Magnet Materials synchronous motor
In recent years, permanent magnet synchronous motors have developed rapidly. They are characterized by high power factor and high efficiency. They have gradually replaced the commonly used AC asynchronous motors in many occasions. Among them, the asynchronous starting permanent magnet synchronous motor has superior performance and is a very popular motor. The future of energy-saving motors.
The stator structure and working principle of the permanent magnet synchronous motor are the same as those of the AC asynchronous motor. The difference from the ordinary asynchronous motor lies in the rotor structure Permanent Magnet Materials. The rotor is equipped with permanent magnet poles. The permanent magnets are arranged in various positions in the rotor.
The development of Permanent Magnet Materials motors is closely related to the development of permanent magnet materials
The world’s first motor that appeared in the 1820s was a permanent magnet motor that generated an excitation magnetic field from Permanent Magnet Materials. However, the permanent magnet material used at that time was natural magnetite (Fe3O4), which had a very low magnetic energy density. The motors made with it were bulky and were soon replaced by electric excitation motors.
With the rapid development of various motors and the invention of current magnetizers, people have conducted in-depth research on the mechanism, composition and manufacturing technology of permanent magnet materials, and have successively discovered various permanent magnet materials such as carbon steel, tungsten steel, and cobalt steel.
In particular, the AlNiCo permanent magnets that appeared in the 1930s and the ferrite permanent magnets that appeared in the 1950s have greatly improved their magnetic properties, and various micro and small motors are using permanent magnets for excitation.
However, the coercivity of AlNiCo permanent magnets is low, and the remanent magnet density of ferrite permanent magnets is not high, which limits their application range in motors. Until the 1960s and 1980s, samarium cobalt permanent magnets and neodymium iron boron permanent magnet materials came out one after another.
Their high remanence density, high coercive force, high magnetic energy product and excellent magnetic properties of linear demagnetization curve are particularly suitable for Manufacture of motors, thus bringing the development of permanent magnet motors into a new historical period.
The relationship between magnetic steel performance and motor performance
1. The influence of residual magnetism
For DC motors, under the same winding parameters and test conditions, the higher the residual magnetism, the lower the no-load speed and the smaller the no-load current; the greater the maximum torque, the higher the efficiency at the highest efficiency point. In actual tests, the level of no-load speed and the size of the maximum torque are generally used to judge the residual magnetism standard of Permanent Magnet Materials.
For the same winding parameters and electrical parameters, the reason why the higher the residual magnetism, the lower the no-load speed, and the smaller the no-load current is because the running motor generates sufficient reverse induction at a relatively low speed. Generates a voltage, causing the algebraic sum of the electromotive force applied to the winding to decrease.
2. The influence of coercive force
During the operation of the motor, there are always effects of temperature and reverse demagnetization field. From the perspective of motor design, the higher the coercivity, the smaller the thickness direction of the magnet. The smaller the coercivity, the larger the thickness direction of the Permanent Magnet Materials.
However, after the coercive force of the magnetic steel exceeds a certain level, it is of no use, because other components of the motor cannot work stably at that temperature. The coercive force only needs to meet the requirements, and meeting the requirements under the recommended experimental conditions is the standard. There is no need to waste resources.
3. The influence of squareness
The squareness only affects the flatness of the motor performance test efficiency curve. Although the flatness of the motor efficiency curve has not yet been listed as an important indicator standard Permanent Magnet Materials, this is very important for the continuation distance of the wheel hub motor under natural road conditions. important. Because of different road conditions, the motor cannot always work at the maximum efficiency point.
This is one of the reasons why the maximum efficiency of some motors is not high but the driving distance is long. A good hub motor should not only have a high maximum efficiency, but also the efficiency curve should be as horizontal as possible Permanent Magnet Materials. The smaller the slope of efficiency reduction, the better. As the market, technology and standards for in-wheel motors mature, this will gradually become an important standard.
4. Impact of performance consistency
Residual magnetism inconsistency: Even some with particularly high performance are not good. Due to the inconsistency of the magnetic flux in each unidirectional magnetic field section, the torque is asymmetric and vibration occurs.
Inconsistent coercive force: Especially if the coercive force of individual products is too low, reverse demagnetization is likely to occur, causing the magnetic flux of each magnet to be inconsistent and causing the motor to vibrate. This effect is more significant for brushless motors.
Effect of magnet shape and tolerance on motor performance
1. The influence of magnetic steel thickness
When the inner or outer magnetic circuit ring is fixed, when the thickness increases, the air gap decreases and the effective magnetic flux increases. The obvious manifestation is that under the same residual magnetism, the no-load speed decreases, the no-load current decreases, and the maximum efficiency of the motor is reduced Permanent Magnet Materials. improve. However, there are also disadvantages, such as the increase in commutation vibration of the motor and the relative steepening of the efficiency curve of the motor. Therefore, the thickness of motor magnets should be as consistent as possible to reduce vibration.
2. Influência da largura do íman
For brushless motor magnets that are densely packed, the total cumulative gap cannot exceed 0.5 mm. If it is too small, it will not be installed. If it is too large, it will cause vibration and reduced efficiency of the motor. This is because the position of the Hall element that measures the position of the magnet and the magnetic The actual position of the steel does not correspond Permanent Magnet Materials, and the consistency of the width must be ensured, otherwise the efficiency of the motor will be low and the vibration will be large.
For brush motors, there is a certain gap between the Permanent Magnet Materials, which is reserved for the mechanical commutation transition area. Although there is a gap, in order to ensure the accurate installation position of the motor magnets, most manufacturers have strict magnet installation procedures to ensure installation accuracy. If the width of the magnet is exceeded, it will not be installed; if the width of the magnet is too small, the positioning of the magnet will be misaligned, the vibration of the motor will increase, and the efficiency will decrease.
3. The influence of magnetic steel chamfering size and non-chamfering
If there is no chamfering, the magnetic field change rate at the edge of the motor’s magnetic field will be large, causing pulse vibration of the motor. The larger the chamfering, the smaller the vibration. However, chamfering generally causes a certain loss of magnetic flux.
For some specifications, when chamfering to 0.8, the magnetic flux loss is 0.5~1.5%. When the residual magnetism of brushed motors is low, appropriately reducing the chamfer size will help compensate for the residual magnetism, but the pulsation of the motor will increase. Generally speaking, when the residual magnetism is low Permanent Magnet Materials, the tolerance in the length direction can be appropriately enlarged, which can increase the effective magnetic flux to a certain extent and keep the performance of the motor basically unchanged.
Permanent magnets used in various applications, including air conditioners, are typically made from materials with high magnetic properties. Here are some common materials used for permanent magnets:
Neodymium Iron Boron (NdFeB): Neodymium magnets are the strongest type of permanent magnets available commercially. They offer high magnetic strength relative to their size and weight, making them suitable for applications where space and weight are constraints. NdFeB magnets are commonly used in motors, generators, headphones, magnetic separators, and various industrial and consumer electronics.
Samarium Cobalt (SmCo): Samarium cobalt magnets are known for their excellent temperature stability and resistance to demagnetization, making them suitable for high-temperature applications. While not as strong as neodymium magnets, SmCo magnets offer superior performance at elevated temperatures. They are used in aerospace, automotive, and medical applications, as well as in motors, sensors, and magnetic couplings.
Alnico (Aluminum-Nickel-Cobalt): Alnico magnets are composed of aluminum, nickel, cobalt, and iron. They have good magnetic properties and high coercivity, making them resistant to demagnetization. Alnico magnets are often used in sensors, guitar pickups, loudspeakers, and various industrial applications.
Ferrite (Ceramic): Ferrite magnets, also known as ceramic magnets, are made from a mixture of iron oxide and barium or strontium carbonate. They are relatively inexpensive and have good resistance to corrosion and demagnetization. Ferrite magnets are widely used in speakers, refrigerator magnets, motors, and magnetic separators.
Bonded Magnets: Bonded magnets are made by mixing magnetic powders, such as NdFeB or ferrite, with a polymer binder. They can be molded into various shapes and sizes, offering flexibility in design and manufacturing Permanent Magnet Materials. Bonded magnets are used in motors, sensors, magnetic assemblies, and consumer electronics.
Each type of permanent magnet material has its own unique properties and characteristics, making it suitable for specific applications. The choice of magnet material depends on factors such as magnetic strength, temperature stability, corrosion resistance, cost, and manufacturing requirements.
