Permanent magnets are essential compounds in various fields of technology due to their potential to offer the magnetic flux deprived of windings and have applications in a huge range of devices like automation applications, electromechanical devices & machines, office equipment, torque applications and mechanical force, computer peripherals, electron-ion beam control sensors, microwave devices, electric and acoustic signal transducers, bioengineering and medical electronics, advertising and transportation.

The advancement of hard magnetic materials is very quick, with the beginning of rare-earth PMs in the last years. The use of magnets in the electrical machines has developed

Permanent magnets are essential compounds in various fields of technology due to their potential to offer the magnetic flux deprived of windings and have applications in a huge range of devices like automation applications, electromechanical devices & machines, office equipment, torque applications and mechanical force, computer peripherals, electron-ion beam control sensors, microwave devices, electric and acoustic signal transducers, bioengineering and medical electronics, advertising and transportation.

The advancement of hard magnetic materials is very quick, with the beginning of rare-earth PMs in the last years. The use of magnets in the electrical machines has developed because of the advancements in magnet features and reduce the prices of the magnet. In the current years, there are several studies done on the advancement of operating and design features of electrical machines with PMs. The design and theory of fractional-slot focused-winding synchronous PM machines with the attributes like flux-weakening potential, high-power density, assessment of single-versus double layer windings, parasitic effects and fault tolerance rotor losses and the comparison of the interior structure against PM machines and other electric machines. China generates around 97% of the world’s rare earth elements, the main constituent in a huge assortment of developed civilian and military technologies. Permanent magnet market involves the data that is accessible as data is complex to acquire or not reliable for magnetic materials. In the enterprise of the electrical machine, proper design of machine and selection of appropriate materials with the compounds, involving magnets are critical.

Characteristics of Permanent Magnet Materials

The characteristics of permanent magnets must be recognized to choose the magnet suitable for various applications. Necessities required by applications ate BHmax, flux density, better demagnetization curve, confrontation to demagnetization, recoil permeability, electrical resistivity, corrosion resistance, less field the requirement of magnetizing, satisfactory magnetization change with temperature, practical temperature range, accessibility in specific shapes and size and manufacturability. The demagnetization curve is the second quadrant of BH curve, mentioning the conditions where PMs are used in practice.

Temperature Properties of Permanent Magnet

The main restraint in the application of magnets is the tolerance of temperature. For permanent magnets, the extreme power density the product of magnetic and electric loadings of the motor are as high as probable. The electric loading is restricted by the thermal factors and the effect of demagnetizing on the magnet. The high electric loading requires a magnet length in the track of magnetization to protect demagnetization. The biggest threat of demagnetization is the low temperatures when remanent flux density is great and the coercivity is less in motor resulting in the largest short-circuit current when the magnet is less able to attack the demagnetizing ampere turns and requires high coercivity leading to the expensive grades of materials, specifically, if the high temperatures are encountered.

Production of Permanent Magnets

The other significant feature of magnets is manufacturability. Permanent magnets are produced by the following methods:

• Calendering
• Extruding
• Casting
• Injection Molding or Pressure Bonding
• Sintering

A comprehensive selection of polymer additives and polymer binders offer flexibility for the production and fulfill the needs of several applications involving the use of electric machines. Many of the fast-growing applications are DVD, CD, HDD applications, wind power generators and electric & hybrid traction efforts. The main usages for rare earth magnets, mainly NdFeB is the electro mechanic devices like DVDs, CDs and hard disk drivers where the magnet is utilized for fueling the spindle motor and putting the write/ read head.

Use of Permanent Magnets in the construction of electrical machines results in following advantages:

• Reduce the prices for some machines
• Interpretation of maintenance and construction
• Good performance than motors with electromagnetic excitation
• Output power/ higher torque per volume on comparing the electromagnetic excitation
• Electrical energy is not absorbed by the excitation system and no excitation losses creating the significant growth in efficacy.

Substituting the field winding and structure with permanent magnets allows the substantial the decrease in the rotor or stator diameter, occurred by the effective usage of radical space by the magnet and eliminate the field losses. The high power density needs the biggest possible magnet volume.

Samarium cobalt is the kind of rare earth magnet material highly resistant to oxidation having high magnetic strength, high corrosion resistance, high instrict coercivity and high remanence. Samarium-cobalt magnet inclines towards the breaking down magnetically at around 800-900°, where the Curie temperature of samarium-cobalt magnets will be substantially degraded. It is recommended to think through the SmCo magnets for the applications of high temperature to the moderate tonnage requirements.

Additionally, it shows the very low variation of field strength with differing temperatures, has better temperature resistance than Alnico material, a very high Curie point and high corrosion resistance.

Analysis of Permanent Magnet machines by using FEM

In this research, 4 poles PM Synchronous Machines are designed. There are total of 8 different PMs used in the rotor of the motor. Hence, around 8 exceptional motor simulations are performed. The costs of functioning the machine and consequence of material properties were examined in the circumstance of using other type materials in rotor magnets of PM motor.

The analyses were carried out for different machines with different magnet dimensions and materials. The magnetic examination of the designed PMSMs, as per the iron sheet package structure with the dimensions of the same magnet utilized in designed motors, were performed. From the electromagnetic analysis, the definite potential magnetic flux intensity of motors was accomplished.

Complete knowledge of the field distribution in the gap of PM motor is important for the precise prediction of efficiency and torque characteristics. The design criteria are selected as the determined efficacy for a machine having the material selection, machine size and magnet size in the account. Various slots, inner-outer and stator diameters, number of contractors in every slot and dimensions of the magnet of a machine constructed for producing the output power improved by targeting for the output of a huge power output machine’s design with supreme efficacy.

Results

After the obligatory simulations, it was observed that to accomplish the size of the machine, dimensions of magnets and number of slots were developed. In the family of Samarium Cobalt, dimensions and magnet of machines are increased. The parameters of the machine, likely the load angle and torque are significant in the examination of electrical machines. On using the torque angle, also labeled as load angle, the important features of the machine can be surveyed.

Air-gap Flux densities of designed machines are determining the degree of harmonics. Air-gap flux densities are achieved after shaping the pole heads, showing that the tightness invested from the stator slots are becoming more accurate.

Conclusion

The general and magnetic study of designed PMSMs with the power of round 0.56kW and speed of around 1600 rpm is changing and the results were associated in terms of size, magnetic field, topology, voltage, air-gap flux, torque, losses, weight, efficacy and speed. As the magnetic field strengths and flux distribution are modeled accurately, it is likely to design more economical and smaller machines. The main objective is to select the economical magnet to consistently reach the goals of design. To construct the machine with the finest efficacy, shape, size and correct selection of magnet material is significant.