The impact of magnetic materials and encoders on the motor manufacturing industry

At present, the upstream of motors is mainly raw materials such as magnetic materials, encoders, chips and bearings; the midstream is motor manufacturing; the downstream is motor application fields, including water equipment, electric power equipment, wind power equipment, thermal power equipment and home appliances, industrial robots, etc. .

Changes in raw material prices in the upstream industry have a greater impact on the product pricing policies, cost levels, and sales performance of motor companies, and are highly correlated. The main raw materials of motor products are electrolytic copper, silicon steel, carbon steel, etc. These industries have mature technologies, sufficient market competition, and sufficient product supply, which can better meet the production and operation needs of the motor industry and provide opportunities for the sustainable development of the motor industry. important guarantee. Downstream motor products are widely used in various fields of the national economy, especially large and medium-sized motors, which are widely used in metallurgy, water conservancy, petrochemicals, building materials, wind power and other industries. The rapid development of related industries has provided a broad market space for the motor industry and promoted the orderly development of the entire motor industry.

Magnetic materials are one of the main raw materials of motors and have a great impact on motor performance.

(1) Motors generally use materials with strong magnetic properties. Strong magnetic materials include permanent magnet materials, soft magnetic materials and functional magnetic materials.

The characteristic of permanent magnets is that once magnetized, it is difficult to demagnetize. Soft magnets are also easy to magnetize, but they are easy to demagnetize after magnetization: permanent magnet materials are currently divided into three categories: metal permanent magnets, ferrite permanent magnets and rare earth permanent magnets. Soft magnetic materials include ferrite soft magnets, metal powder cores, metal soft magnets and amorphous nanocrystals. The most different characteristic of the two magnetic materials is their different coercive forces. Coercive force is defined as the external magnetic field strength that must be applied in the opposite direction to the original magnetization to prevent the magnetized magnetic material from providing energy to the external magnetic circuit (but there is still a certain amount of energy inside the magnet). The unit is Oe or A/m. .

(2) The higher the coercivity, the less likely the material is to demagnetize

The goal of permanent magnet materials is to continuously pursue higher coercive force and strengthen the ability not to demagnetize, and are widely used in permanent magnet motors; soft magnets can play an important role in electrical energy parameters by reducing coercive force and pursuing higher magnetic permeability. Transform, improve the efficiency of magnetic components and save space. Currently, magnetic cores are used as components in various types of motors, transformers, relays, inductors, filters, etc. in new energy vehicles, robots, photovoltaics, and many other fields.

(3) NdFeB has better performance and the permeability is expected to increase

NdFeB material has excellent performance in coercive force and is also superior to other materials in magnetic energy product. Better magnetic energy product also means that the size of NdFeB is smaller per unit magnetic field intensity, which is also very helpful in saving motor space. In particular, high-performance NdFeB magnetic materials (the sum of coercive force and magnetic energy product is greater than 60) can greatly reduce the size of the motor, reduce the mass of the motor, reduce the energy loss of the motor and improve the efficiency of the entire motor system. The only disadvantage is that the temperature stability is relatively poor, and other elements such as cobalt need to be added to improve the temperature performance, and the price is relatively high.

Encoder

(1) The resolution and accuracy of the encoder are closely related to the motor motion control performance

An encoder is a device that compiles and converts signals into a signal form that can be used for communication and transmission, such as generating actual measured values of speed or position for closed-loop control of a servo motor.

(2) Encoder classification

There are many types of encoders, which can be divided into contact and non-contact according to the reading method; according to the detection working principle, servo motor encoders can be mainly divided into photoelectric encoders, magnetic encoders, inductive encoders and capacitive encoders. device. Among them, optical encoders based on the principle of photoelectric conversion and magnetic encoders based on the principle of magnetic field changes induced by magnetic sensitive elements are widely used.

1) A photoelectric encoder consists of an LED light source (usually an infrared light source) and a photodetector, both of which are located on both sides of the encoder disc. The code wheel is made of plastic or glass with a series of light-transmitting and opaque lines or grooves arranged at intervals. When the code wheel rotates, the LED light path is blocked by the spaced lines or slots on the code wheel, thus generating two typical square wave A and B orthogonal pulses, which can be used to determine the rotation and speed of the shaft.

2) The principle of the magnetoelectric encoder is to use magnetoresistive or Hall elements to measure the angle or displacement value of the changing magnetic material. Changes in the angle or displacement of the magnetic material will cause a certain change in resistance or voltage. The change is amplified through an amplification circuit, and the pulse signal or analog signal is output after processing by the microcontroller to achieve the purpose of measurement. The number of magnetic poles of the magnetic turntable, the number of magnetoresistive sensors and the signal processing method determine the resolution of the magnetic encoder, so that the magnetic field signal will not be affected by dust, moisture, high temperature and vibration.

Optical encoders generally have high accuracy and high cost, and have certain requirements for industrial environments. Dust, water vapor, etc. may affect the accuracy of the encoder; magnetic encoders are relatively simple in cost and have a relatively obvious price advantage.