MATERIAL SELECTION AND SOFTWARE SIMULATION OF DESIGNED PERMANENT MAGNET GENERATOR.

This paper presents a study on material used for the proposed design of Permanent Magnet Synchronous Machine (PMSM) and the 2D (Two Dimensional) analysis of Magnetostatics analysis for the designed model in software. It is more important to consider material selection and analysis for the accountancy of loss in the permanent magnet synchronous machines as they are having higher power output density. It is also necessary that an EM (Electromagnetic) field analysis accounting for the temperature rise throughout the machine should be taken into account because the heat generation from these loss transfers to the inside of the machine’s structure causing changes in material properties, temperature rise in machine winding and finally an enormous impact on the machine characteristics.

This paper presents a study on material used for the proposed design of Permanent Magnet Synchronous Machine (PMSM) and the 2D (Two Dimensional) analysis of Magnetostatics analysis for the designed model in software. It is more important to consider material selection and analysis for the accountancy of loss in the permanent magnet synchronous machines as they are having higher power output density. It is also necessary that an EM (Electromagnetic) field analysis accounting for the temperature rise throughout the machine should be taken into account because the heat generation from these loss transfers to the inside of the machine's structure causing changes in material properties, temperature rise in machine winding and finally an enormous impact on the machine characteristics.

…………………………………………………………………………………………………….... Introduction: -
Material selection is one of the major factors while designing a rotating electrical machine. In the function of energy conservation material plays an important role as all the calculations of designing is done on the basis of properties of material selected. In order to gain high power density current Permanent Magnet Synchronous Machines (PMSM) work with a high flux in the airgap and therefore high flux densities in stator and rotor parts. Manufacturing process will also have effects on the final properties of the parts of the machines. During manufacturing the laminations are punched out of the coil to the desired shape. Attention has to be paid not only to the design but also on the manufacturing technique itself [1]. It is observed that manufacturing techniques such as laser cutting for prototyping or stamping during production will have the negative influence on the local magnetic properties of the material. This will result in iron loss depending on the manufacturing technique used. The different cutting methods will introduce mechanical stress in the material, resulting into locally decreasing magnetic permeability of magnet. On the other hand, it is also important that machine will have good mechanical and electrical properties which will make machine more efficient. Considering the losses due to manufacturing techniques and other losses such as iron loss, copper loss, stray loss and many more it is important to perform magnetic analysis of the machine for the acknowledgment of losses in the machine. During the development of rotating electrical machines. The major challenge is faced in the problem caused by the heat generation in the different parts of the machine, and it is not easy to specify and calculate the production of heat due to magnetic fields of magnetic material used in the machine. The thermal characteristic of IPMSM (interior permanent magnet synchronous machine) is very important as the generation of heat will affect the insulation of the winding, causing change in magnetic properties of magnet or demagnetizing of magnet. For the study of the effects 2D analysis of electromagnetic analysis is done in "MOTOR ANALYSIS -PM" and "MAGNET" software.\

A. Structural Information
Our proposed designed PMSM will be a closed ends drum type structure made from nylon polymer and having permanent magnets on both stator and rotor. There will be a concentric winding for the generation of electromotive force. Other mechanical supporters like supporting members, bearings, conductor covers are also a part of structural design of machine.

B. Material Selection
As stated, earlier material selection is such type of process which will help to eliminate unnecessary losses resulting into increase in efficiency. Selection of body material for the machine will have greater impact on iron losses of the machine because any metallic part of the machine will have greater or lesser contribution in iron loss of the machine. Nylon 66 is synthetic polymer called polyamides, with the numbers describing the type and quantity of polymer chains in their chemical structure [2]. Most nylons, including 6 & 66, are semi-crystalline. Nylon 66 should be used if a high performing engineering plastic is required that will be exposed to higher temperatures. Normally it is used in textile industry, friction bearings, radiator caps and tire ropes because of its advantages.
Properties of Nylon-6 material is sown in Generation of proper magnetic field is the major factor affecting the performance of any PMSM [4]. Use of rare earth magnets will give higher magnetic field than using electromagnets. And also, rare earth magnets will have longer life span. Table 2 shows the main magnetic characteristics of different rare earth magnets [7] for the selection of proper magnets for the working of machine. It is seen that Neodymium magnets have the best magnetic characteristics among all other magnets.

Magnet
Remanance ( Crystal structure of the neodymium magnet is composed of microcrystalline grains that are aligned in a powerful magnetic field during manufacture so their magnetic axes all point in the same direction. The crystal lattice of the magnet resists to turning its direction of magnetization which makes this compound highly coercive to demagnetize.

Property
Neodymium Remanence (T) 1-1.3 Relative permeability(µ r ) 1.05 Coercivity (MA/m) 0.875-1.99 Table 3 -Properties of Neodymium magnet Fig. 1 depicts the values of remanence and coercivity of the neodymium magnet over its entire working temperature range. The working temperature range for NdFeB is fromto . It can work intrinsically at very lower temperature and can work normally at very higher temperature. Due to its wide working temperature range it is more preferred over other magnets for the higher magnetization though they are little bit costly from other rare earth magnets.  Table 4 shows the specifications of 1 kW interior PMSM [6]. The 2D model shown in fig. 2 depicts the real geometry of the interior PMSM which is having shaft, rotor, permanent magnets, stator core. And in fig 3, fig 4 and   Maxwell's equations are used to get the magnetic phenomena in the machine. Overall, the motor characteristics in 2D and 3D analyses are very similar, ignoring some differences such as the leakage flux occurred in end-windings and slot leakage reactance which depends on the winding shape in the slot. However, the copper loss in the coils and iron loss in the core are the main heat sources. Flux passing through axial axis of the machine and current flowing through end winding must be considered in order to measure losses [3].

C. Specification of Analysis model
Generation of heat due to passing of current in winding coils having resistance R can be expressed by using joule's heat loss equation: Thus, heat generated is directly proportional to the square of current passing through the winding and resistance divergent increases with increase in temperature.
Iron loss (hysteresis loss) in the machine can be expressed by steinmetz equation: Where f is the frequency of flux reversal and V is the volume of core of the machine.  figure 7 which gives conclusion that our selected magnet will give the least loss full operation.

Conclusion:-
This paper gives the detailed study on material selection for the PMSM and gives its magnetostatic analysis for the different loss calculation. It is proposed that nylon type polymer material can be used for the small rated machine as it is having all required qualities and can eliminate the major iron losses. High graded rare earth magnetic material can be used to achieve high power density in machine. This proposed model is under designing stage and further detailed study and improvement in material selection and magnets can be led to more and more efficient machine.