What is Halbach Array Linear Motor

Traditional motors such as DC motor, synchronous motor, induction motor, and variable reluctance motor can be used as electromagnetic actuators, but using rotating motor as actuator has advantages and disadvantages. DC motor control is simple, but the existence of brush makes DC motor need to be maintained regularly and not suitable for vacuum working environment; induction motor control is more difficult; variable magnetism motor. The cogging force caused by the cogging of the resistance motor will bring the difficulty to precision positioning.

Synchronous motors are more suitable for lithographic operation. In order to avoid magnetic resistance and cogging force, they can adopt the structure without iron, cogging and winding surface mounting.

synchronous motors

The traditional planar positioning system transforms the rotating motion of rotating motor into linear motion by gear, ball screw, and other transmission mechanisms. Because of the problems of backlash, friction and uncertain ball motion, it is difficult to carry out high precision positioning. As a result, technicians are forced to relocate on the workbench. A precise worktable is set up for micro-displacement correction. This kind of multi-action substructure positioning platform has a huge system and slow response.

In high precision plane motor control, compared with rotary motor drive, the direct drive of permanent magnet linear motor has the advantages of no mechanical noise and additional transmission error; no additional mass, such as lead screw, can obtain greater acceleration and faster response; linear motor can not only produce unilateral force but also can produce. The vertical force can be used as a two degree of freedom actuator. Ordinary permanent magnet linear motor only uses the single-layer primary magnet. The harmonic component of the magnetic field along the space is large and the amplitude of fundamental component is small, so it can not produce large electromagnetic force. Ordinary permanent magnet linear motor adopts three-phase control. The winding arrangement is complex, the winding end effect is large, and the cooling condition is poor, which affects the operation of the linear motor.

linear motor

The magnetic field of Halbach permanent magnet array shows obvious unilateral characteristics. The magnetic field on one side is significantly enhanced, and on the other side is significantly weakened. The magnetic field on the strong side has good sinusoidal distribution characteristics, and the high-order harmonics are small. The linear motor with Halbach permanent magnet arrays can improve some shortcomings of ordinary permanent magnet linear motor.

The Neodymium Halbach Arrays are specialized magnetic assembly consisting of Neodymium Iron Boron (NdFeB, NIB, Neo) permanent magnets assembled in such a way as to provide a controlled (uniform and homogenous) and high magnetic field strength without the use of ferromagnetic materials.

This Halbach Array is a cylinder / ring-shape with a dipole (2 poles) pattern in the central air gap. The magnetic field within the ring is uniform (parallel field lines which are homogenous) across the entire central hole and of high strength (above 10000 Gauss or 1 Tesla), both being features of this style of Halbach Arrays.

The Neodymium Halbach Array ring magnet is made from 8 magnets (45-degree arc segments, each with a specific direction of magnetization). Each arc part has the direction of magnetization such that the magnetic field traverses the central air gap and is then ‘guided’ through and around the magnet material itself.

How does magnets and voice coil motors work?

Mechanical Integrity

The design of voice coil motors ensures good concentricity and mechanical integrity of the complete device. Accurate fixtures are used in assembly to control assembly dimensions, and coil magnet assemblies are individually measured to ensure concentricity and clearance with the magnet assembly. All devices are designed to ensure that finite clearances are maintained throughout an operating range from 0ºC to 130ºC.

If a conductor (wire) carrying the electric current is placed in a magnetic field. A force is generated on the wire at right angles to both the direction of current and magnetic flux. The Lorentz force is proportional to the product of the magnetic field and the current, in a direction perpendicular to both of them.

In the diagram this direction would be directly toward us. If the current were reversed it would be directly away from us.

Coil wire magnetic field

If the wire were free to move it would accelerate toward us all along its length. Since the permanent magnet flux density field is fixed, the direction of the linear displacement depends on the polarity of input current.

If the magnetic field and conductor length are constant, then the generated force is directly proportional to the magnitude of the current applied to it.

voice coil motor VCM

A simple linear voice coil motor consists of a tubular coil of wire. The wire is situated within a magnetic field. The magnetic field is produced by permanent magnets embedded on the inside diameter of a ferromagnetic cylinder.

The cylinder is arranged such that the side of the magnets that faces the ferromagnetic cylinder has the same polarity as the cylinder. The opposite side of the magnets facing the coil has the opposite polarity. An inner core of ferromagnetic material set along the axial centreline of the coil, joined at one end to the permanent magnet assembly, is used to complete the magnetic circuit.

When coil current flows, force is generated. The axial force generated along the coil will produce relative motion between the field assembly and the coil. But the force should be large enough to overcome friction, inertia and any other loads attached to the coil.

Electrical Termination

Connection to the moving coil of a voice coil motor must be implemented with care to ensure reliable operation. Flexible cable with many fine strands and Silicone Rubber insulation can provide reliable termination, care should be taken that the leads are mechanically secured to the moving assembly preferably at some distance from the soldered joints (solder fuses the strands together, and leads to large stresses being applied to the termination pins, or to fatigue adjacent to the fused portion of the wire). The leads should be carefully routed to minimise stress. A more consistent means of termination is to use a flexible circuit, this option is offered for several of the VCM devices.

For more information, please visit https://www.stanfordmagnets.com/

What is Permanent Magnet Motor?

Magnetic Assembly—Permanent Magnet Motor

The Permanent Magnet Motor includes
– armature with split ring commutator at one end
and a dual slip-ring commutator at the other
– field magnet, shaft and brush assembly
– maintenance items
– manual
ceramic magnet

The Permanent Magnet Motor can be used to demonstrate the operation of a DC motor. The Permanent Magnet Motor can be used to determine the speeds of maximum power and maximum efficiency of a DC motor by varying the load while simultaneously measuring the speed, torque, and armature current.

magnet motor

The field magnets are permanent magnets possessing a north pole and a south pole that interact with the north and south poles of the armature (an electromagnet when connected to an electric current). Like poles repel, while unlike poles attract. The armature rotates until its north pole is as close as possible to the south pole of the permanent magnet (and also as far as possible from the north pole). Inertia carries the armature past this point.

However, as the armature passes this point, the commutator reverses the direction in the coils, so that the poles of the coils are suddenly repelled by the nearby field magnets. Thus another half-turn occurs, and this process occurs again and again.

A better explanation involves an understanding of fields. The field magnets produce a magnetic field that passes through the gap between the pole pieces. When current passes through the turns of the armature in the presence of the field, forces act to cause a torque that rotates the armature.

Inertia carries the armature past the position of no torque to the point where the torque would force the armature back in the other direction. However, at that point the commutator reverses the direction of current in the armature so the torque continues to act in the original direction.

How to start a simple motor?
The motor is not self-starting. Immediately after you apply the power, start the motor manually by grasping the black plastic bushing at the top of the armature assembly between your thumb and forefinger and spinning the armature.

With the Permanent Magnet Motor configured as either a DC or universal motor, almost any attempt you make at spinning the armature will result in successfully starting the motor; only the direction of the spin is important.

When configured in an AC synchronous mode, the motor must be spun at a speed that approximately matches the frequency of the power source.

Halbach Array For Magnetic Bearings

Klaus Halbach has been investigating novel designs for permanent magnet arrays for many years, he used advanced analytical approaches to employ a keen insight into such systems. One of his motivations for this research was to find more efficient means for the utilization of permanent magnets for use in particle accelerators and in the control of particle beams.

radial Halbach magnetic bearing rotor

As a result of his pioneering work, high power free electron laser systems, such as the ones built at the Lawrence Livermore Laboratory, became feasible, and his arrays have been incorporated into other particle focusing systems of various types. This paper reports another, quite different, application of Klaus’ work, in the design of high power, high efficiency, electric generators and motors.

When tested, these magnet motor or generator systems display some rather remarkable properties. Their success derives from the special properties which these arrays, which we choose to call “Halbach arrays,” possess.

Halbach-arrays are widely used in the passive magnetic bearings. The nowadays industrial rotor machines are more flexible and often operating with ultra-high speed. Using the passive magnetic bearings in certain applications, we need to take into account the occurrence of radial component in the case of axial bearings and axial component in the case of radial bearings.

Journal bearings, in addition to passing load forces of the rotor, rotor weight and damping must take into account the existence and impact of this negative component forces. Therefore, in the design of passive bearings Halbach-arrays are introduced.

Halbach array is a special setup and configuration of permanent magnets so that you can get the concentration of magnetic flux in a specific, desired item, and remove it from less important or unwanted places.

Among the Halbach arrays, to guide the magnetic field in the desired way, we can distinguish boards between 180° and 90°. These terms relate to the relationship between the magnetization vectors.

Halbach magnetic bearing rotor

In the construction of the passive radial magnetic bearing 180° Halbach-array was used. This kind of magnetic bearings belongs to the repulsive magnetic bearings.

The examined passive magnetic bearing is composed of four pairs of the neodymium-iron-boron (NdFeB) magnets rings. These rings are axially magnetized, which means that magnetic poles are placed on the flat circle sides of the magnets.

The introduction of the Halbach-arrays allows the adequate orientation of the magnetic field in the placenta, and to reduce the negative impact of the active component forces. The use of Halbach-arrays and magnetic bearings, allow to develop and to implement the high performance passive magnetic bearings.

What Should We Know About Magnets?

Magnets are composed of iron, cobalt, nickel and other atoms, the internal structure of the atom is relatively special, it has a magnetic moment. Magnets can produce magnetic fields and attract the properties of ferromagnetic materials such as iron, nickel and cobalt.

Different types of magnets have different uses.

Classification of magnets:

Shape magnets: square magnet, arc magnet, special-shaped magnet, cylinder magnet, ring magnet, disc magnet, bar magnet, magnetic frame magnet.

Attribute magnets: SmCo magnets, NdFeB magnets (powerful magnets), ferrite magnets, AlNiCo magnets, Fe-Cr-Co magnets;
Industry magnets: magnetic components, motor magnets, rubber magnets, plastic magnets and so on.

Magnets are divided into permanent magnets and soft magnets. Permanent magnets are added with strong magnets, so that the spin of magnetic materials and the angular momentum of electrons are arranged in a fixed direction. Soft magnets are added with electricity. It is also a way of adding a magnetic force. If the current is removed, the soft iron will slowly lose magnetism.

powerful magnets

The use of different types of magnets:

1. Neodymium iron boron permanent magnet is a modern permanent magnet with strong magnetism, and its application is also extensive.

It is mainly used in electroacoustics, permanent magnet rotor, communications, automotive electronics, magnetic machinery, aerospace, computer, household appliances, medical equipment, office automation, toys, packaging boxes, leather products, magnetic accessories and other fields.

custom neo magnets

2. Permanent magnet ferrites are used as permanent magnets in electric meters, generators, telephone sets, loudspeakers, television sets and microwave devices. They are also used in recorders, pickups, loudspeakers, and magnetic cores of various instruments. They are used in radar, communications, navigation, telemetry and other electronic devices.

3. SmCo magnets can operate at temperatures up to 300 degrees, and have corrosion resistance and oxidation resistance. They have been widely used in detectors, generators, radar, instrumentation, and other precision science and technology fields.

4. Al-Ni-Co magnets are high temperature resistant and corrosion resistant. They are mainly used in motors, sensors, medical instruments, manual tools, loudspeakers and various instruments.

5. Rubber coated magnets have the same and different characteristics, the same suction is weak, mainly used for publicity (refrigerator stickers, car stickers, etc.), decorative gifts, refrigerator stickers, toys, teaching materials and other areas.

Which Magnet is Used for Industrial Purpose

Nd-Fe-B magnetic materials, as the latest development of rare earth permanent magnets, are called “magnetic king” because of their excellent magnetic properties. Fe-B is the best magnet with small volume, lightweight and strong magnetism. Major materials for producing NdFeB high-strength magnets are neodymium, pure iron, ferroboron alloy and other additives.

In the healthcare industry, lots of practice and scientific experiments have proved that high-intensity magnetization of neodymium iron boron magnet can change the surface tension, density, solubility and other physical properties of water, and have a significant impact on chemical properties such as acid and alkali. Magnetized water can increase the activity of enzymes in water and permeability of biofilm, often drinking can strengthen health care. Regulate the human body’s microcirculation system, digestive system, endocrine system, and nerve function, improve human immunity, prevent and treat a variety of diseases.

NdFeB magnetic materials

In the scale removal and anti-scaling industry, the angle and length of water molecular bond are deformed simultaneously after high-intensity magnetization of NdFeB. The hydrogen bond angle is reduced from 105 to 103 degrees, which changes the physical and chemical properties of water.

The activity and solubility of water are greatly improved. Calcium carbonate in water is decomposed into lower and soft calcium bicarbonate during cooking. It is not easy to accumulate on the wall and easy to be taken away by water. In addition, the degree of polymerization of water increases, and the dissolved solid matter becomes finer particles. When the particles are refined, the distance between the two ions is smaller, and it is not easy to coagulate on the wall, thus achieving the effect of scale removal.

Environmental protection and energy saving of neodymium cylinder magnet is becoming an important factor affecting the development of manufacturing industry in various countries, and neodymium is one of the main raw materials for environmental protection and energy saving products. For example, the application of NdFeB in automobiles, compressors, wind turbines and other fields is precisely for the consideration of environmental protection and energy conservation.

NdFeB will be more widely used as a functional material for environmental protection and energy saving. In an era of increasing energy shortage, the conversion of wind energy into electricity will undoubtedly be supported by government policies. Wind power generation is now being implemented on a large scale in Europe. The previous one-megawatt unit used about one ton of NdFeB. Thanks to the rapid growth of the wind power industry, the amount of NdFeB used in wind turbines will also be increased rapidly.

Nd-Fe-B magnetic materials, as the latest development of rare earth permanent magnets, are called “magnetic king” because of their excellent magnetic properties. Nd-Fe-B magnet has the characteristics of small volume, lightweight and strong magnetism. It is the best cost performance magnet so far.

How to store magnet?

1. Powerful magnets should not be close to electronic equipment, otherwise, it will affect the control circuit and use of the electronic equipment.

2. Magnets should not be stored in a humid environment to avoid oxidation, resulting in changes in appearance, physical properties, and magnetic properties.

3. If a sensitive object to a metal object approaches a magnet, it will be rough and red. If the above reaction occurs, please do not touch the strong magnet.

4. Do not close the magnets to floppy disks, hard drives, credit cards, tapes, debit cards, television tubes, etc. If the magnet is close to the magnetic recorder and other devices, it will affect or even destroy the recorded data.

New Discoveries of Magnets in Battery Applications

Application of magnet in the battery field

In recent years, power generation bacteria have become a hot topic. Scientists have discovered that bacteria found on the global seabed and river bed can harvest electrons from tiny metal particles. By donating electrons to bacteria, iron particles become an effective source of energy for cells. Other types of bacteria make new discoveries in the field of batteries by “dropping” excess electrons onto metal particles to effectively breathe electrons.

magnet battery

James Byrne and colleagues from the University of Tibingen in Germany have discovered that a common magnetic mineral, the tiny, powerful magnetite grains, can act as both an electron acceptor and an electron donor, thus working as efficiently as a battery. He allowed a community of Enterobacteria and Rhodopseudomonas bacteria to grow on magnets, and then discovered that Enterobacteria could “drop” electrons onto crystals from which Rhodopseudomonas obtained electrons.

For bacterial communities, magnetite crystals act like natural rechargeable batteries: charged by terrestrial bacteria, and consumed by Rhodopseudomonas. Depending on the needs of bacteria, powerful magnets can be used as conductors or as “storage tanks” and sources of electrons.

New magnets can be used to develop the new generation of sensors and actuators.

Researchers at Temple University and the University of Maryland have discovered a new type of magnet that expands in size when placed in a magnetic field and wastes negligible amounts of heat during energy collection. This new discovery has tremendous application potential and is expected to not only replace existing technologies, but also create new applications.

Hash Depp Chopra, chairman of the Department of Mechanical Engineering at Temple University and director of the Laboratory of Materials Genomics and Quantum Devices, and Manfred Utig, professor of materials science and engineering at the University of Maryland, published their findings in the 21st issue of Nature. “Our findings fundamentally changed our understanding of a particular type of magnet that we have known since 1841,” Chopra said.

In the 1940s, British physicist James Joule discovered that when placed in a magnetic field, ferromagnetic materials changed their shape, but their volume remained unchanged. This phenomenon is called “Joule magnetostriction” and has been shown in all magnets for 175 years since its discovery.

“We have discovered a new class of magnets, which we call non-Joule magnetostrictive magnets. In the magnetic field, their volume has changed greatly. Moreover, these non-joule magnets have the extraordinary ability to collect or convert energy with minimal heat loss,” Chapla said.

Chopra and Utig heated a specific iron-based alloy in a furnace to about 760 degrees Celsius for 30 minutes, then cooled it to room temperature quickly, which was when the material exhibited non-joule magnetostrictive behavior.

They found that the heat-treated materials contained tiny honeycomb-like structures that had never been seen before, which was the key to their non-Joule magnetostriction in magnetic fields. “Knowing this unique structure will enable researchers to develop new materials with the same properties,” Utig added.

The researchers pointed out that the conventional rare earth magnet could only be used as an actuator to exert force in one direction due to the Joule magnetostriction. Even if actuated in only two directions, a large number of bulky magnets are required, which increases volume and decreases efficiency. Non-joule magnets can expand in all directions at the same time, so making compact omnidirectional actuators will be easy to achieve.

Because these new magnets also have energy-saving characteristics, they can be used to create a new generation of sensors and actuators with very low heat loss, and can be used in aerospace, automotive, biomedical, national defense, space exploration, and robotics and other fields.

Researchers also say the new magnet contains no rare earth elements, so it can replace the existing expensive but low mechanical properties of rare earth-based magnetostrictive materials.