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Fig. 3 Sample preparation steps: (a) isolating (b) secondary winding, (c) isolating and (d) the primary winding The electrical resistivity of the material (specimens) of the alloys was determined by calculating the electrical resistance. For this measurement, it was used a device called multimeter, which directly measures the electrical resistance of the body. However, for very low electrical resistance measurement, one applies a tension in the specimen and the electrical current is then measured. Therefore, the sample for the determination of the resistivity should be in the form of a thin and long bar. One method is the use of a ring, by cutting a segment of it, making this the shape of a curved bar, ie great length and small cross-sectional area. Ohm's Law states that [22]:

Figure 3 Sample preparation steps: (a) isolating (b) secondary winding, (c) isolating and (d) the primary winding The electrical resistivity of the material (specimens) of the alloys was determined by calculating the electrical resistance. For this measurement, it was used a device called multimeter, which directly measures the electrical resistance of the body. However, for very low electrical resistance measurement, one applies a tension in the specimen and the electrical current is then measured. Therefore, the sample for the determination of the resistivity should be in the form of a thin and long bar. One method is the use of a ring, by cutting a segment of it, making this the shape of a curved bar, ie great length and small cross-sectional area. Ohm's Law states that [22]:

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Fig.1 - Samples in the form of ring - (a) Die - (b) Specimen. (scale in centimeters). The definition of the alloy to be used in rotor and stator cores of the machine was based on a study of the physical properties of some sintered alloys such as FeP, FeNi and FeSi and their variations. In order to analyze the magnetic properties and electrical resistivity, it was used the die of Figure 1a, where specimens were obtained in the form of rings (Figure 1b).
Fig.1 - Samples in the form of ring - (a) Die - (b) Specimen. (scale in centimeters). The definition of the alloy to be used in rotor and stator cores of the machine was based on a study of the physical properties of some sintered alloys such as FeP, FeNi and FeSi and their variations. In order to analyze the magnetic properties and electrical resistivity, it was used the die of Figure 1a, where specimens were obtained in the form of rings (Figure 1b).
Fig. 2 - Samples in the form of cylinder - (a) Die - (b) Specimen. In turn, analysis of the hardness and yield stress of the studied alloys was made concerning the use of the die shown in Figure 2a, where specimens were obtained in the shape of a cylinder (Figure 2b).
Fig. 2 - Samples in the form of cylinder - (a) Die - (b) Specimen. In turn, analysis of the hardness and yield stress of the studied alloys was made concerning the use of the die shown in Figure 2a, where specimens were obtained in the shape of a cylinder (Figure 2b).
Fig.4 — Segmented ring for measuring electrical resistivity. To evaluate the vibration resistance of a material to be used in a rotating electrical machine, it was also carried out mechanical tests on specimens. Hardness tests (HB) were performed in England Precision durometer with indenter of 2.5 mm of sphere and 187.5 kgf load according to norm ASTM E10 [23]. Compression tests were conducted on a universal testing machine EMIC DL20000, using a speed of 2.0 mm/min in accordance with norm ASTM E9 [24].
Fig.4 — Segmented ring for measuring electrical resistivity. To evaluate the vibration resistance of a material to be used in a rotating electrical machine, it was also carried out mechanical tests on specimens. Hardness tests (HB) were performed in England Precision durometer with indenter of 2.5 mm of sphere and 187.5 kgf load according to norm ASTM E10 [23]. Compression tests were conducted on a universal testing machine EMIC DL20000, using a speed of 2.0 mm/min in accordance with norm ASTM E9 [24].
Fig. 7 — Magnetization Curve sintered pure iron. Fig. 8 — Hysteresis loop of sintered pure iron.
Fig. 7 — Magnetization Curve sintered pure iron. Fig. 8 — Hysteresis loop of sintered pure iron.
Fig. 6 — Topology of rotors studied - (a) salient poles with magnets on the surface of the saliences - (b) straight poles with magnets on the rotor surface - (c) embedded magnets within the rotor.
Fig. 6 — Topology of rotors studied - (a) salient poles with magnets on the surface of the saliences - (b) straight poles with magnets on the rotor surface - (c) embedded magnets within the rotor.
Table 1 — Physical properties of the sintered alloys studied
Table 1 — Physical properties of the sintered alloys studied
Figure 9 shows the amplitude in module of the air-gap induction and Figure 10 depicts the lines of magnetic flux generated in the longitudinal plane of the machine for rotor configuration of the salient poles and M15 steel sheets in the rotor. In turn, Figures 11 and 12 present the same data for rotor with sintered Fe-2%P alloy. Fig. 9 - Machine simulation with rotor of salient poles from M15 steel sheet - Air-gap flux density.
Figure 9 shows the amplitude in module of the air-gap induction and Figure 10 depicts the lines of magnetic flux generated in the longitudinal plane of the machine for rotor configuration of the salient poles and M15 steel sheets in the rotor. In turn, Figures 11 and 12 present the same data for rotor with sintered Fe-2%P alloy. Fig. 9 - Machine simulation with rotor of salient poles from M15 steel sheet - Air-gap flux density.
Fig. 10 - Machine simulation with rotor of salient poles from M15 steel sheet - Flux lines in the longitudinal plane of the machine.
Fig. 10 - Machine simulation with rotor of salient poles from M15 steel sheet - Flux lines in the longitudinal plane of the machine.
Fig. 11 - Machine simulation with rotor of salient poles from Fe-2%P sintered - Air-gap flux density.
Fig. 11 - Machine simulation with rotor of salient poles from Fe-2%P sintered - Air-gap flux density.
Fig. 12 - Machine simulation with rotor of salient poles from Fe-2%P sintered - Flux lines in the longitudina plane of the machine. ‘igure 13 shows the amplitude in module of the air-gap induction and Figure 14 presents he lines of magnetic flux generated in the longitudinal plane of the machine for rotor onfiguration of the straight poles and M15 steel sheets in the rotor. Figures 15 and 16 show the same data for rotor with sintered Fe-2%P.
Fig. 12 - Machine simulation with rotor of salient poles from Fe-2%P sintered - Flux lines in the longitudina plane of the machine. ‘igure 13 shows the amplitude in module of the air-gap induction and Figure 14 presents he lines of magnetic flux generated in the longitudinal plane of the machine for rotor onfiguration of the straight poles and M15 steel sheets in the rotor. Figures 15 and 16 show the same data for rotor with sintered Fe-2%P.
Fig.13 — Machine simulation with rotor of straight poles from M15 steel sheet - Air-gap flux density.
Fig.13 — Machine simulation with rotor of straight poles from M15 steel sheet - Air-gap flux density.
Fig.15 — Machine simulation with rotor of straight poles from Fe-2%P sintered - Air-gap flux density.
Fig.15 — Machine simulation with rotor of straight poles from Fe-2%P sintered - Air-gap flux density.
Finally, Figure 17 shows the amplitude in module of the air-gap induction and Figure 18 depicts the lines of magnetic flux generated in the longitudinal plane of the machine for the configuration with embedded magnets and M15 steel sheets in the rotor, while Figures 19 and 20 show the same data for rotor with sintered Fe-2%P. Fig. 17 - Machine simulation with rotor of embedded magnets from M15 steel sheet - Air-gap flux density.
Finally, Figure 17 shows the amplitude in module of the air-gap induction and Figure 18 depicts the lines of magnetic flux generated in the longitudinal plane of the machine for the configuration with embedded magnets and M15 steel sheets in the rotor, while Figures 19 and 20 show the same data for rotor with sintered Fe-2%P. Fig. 17 - Machine simulation with rotor of embedded magnets from M15 steel sheet - Air-gap flux density.
Table 2. Air gap flux density and torque In the simulations performed statically, the instantaneous torque and the magnetic flux in he core of Fe-2% P alloy for both topologies (salient poles and straight poles) resulted in values close to those related to traditional laminated steel sheets. The equivalence among he results is probably due to high values of magnetic permeability, saturation induction and resistivity, as well as low coercivity displayed in electric and magnetic tests [39]. In a rotating electrical machine working as a motor or generator, the torque on the shaft is a function of the magnetic flux air gap (maximal induction) and the inclination of the magnetic flux lines in the air gap, also known as load angle for the case of rotating synchronous electric machines. A rotating electrical machine is, therefore, a dynamic transducer energy, ie as motor, it transforms electrical energy from the armature windings into mechanical energy delivered to a load on the shaft. In a generator, the opposite takes place, i.e. it transforms mechanical power on the shaft from a turbine, for example, into electrical energy. In both cases, the conversion of mechanical energy to electrical and vice versa occurs from the magnetic field, and the magnetic flux of air gap (or maximum Table 2 shows the maximum values of air gap flux density and torque developed on the shaft, considering the machine functioning as motor.
Table 2. Air gap flux density and torque In the simulations performed statically, the instantaneous torque and the magnetic flux in he core of Fe-2% P alloy for both topologies (salient poles and straight poles) resulted in values close to those related to traditional laminated steel sheets. The equivalence among he results is probably due to high values of magnetic permeability, saturation induction and resistivity, as well as low coercivity displayed in electric and magnetic tests [39]. In a rotating electrical machine working as a motor or generator, the torque on the shaft is a function of the magnetic flux air gap (maximal induction) and the inclination of the magnetic flux lines in the air gap, also known as load angle for the case of rotating synchronous electric machines. A rotating electrical machine is, therefore, a dynamic transducer energy, ie as motor, it transforms electrical energy from the armature windings into mechanical energy delivered to a load on the shaft. In a generator, the opposite takes place, i.e. it transforms mechanical power on the shaft from a turbine, for example, into electrical energy. In both cases, the conversion of mechanical energy to electrical and vice versa occurs from the magnetic field, and the magnetic flux of air gap (or maximum Table 2 shows the maximum values of air gap flux density and torque developed on the shaft, considering the machine functioning as motor.
Fig. 19 — Machine simulation with rotor of embedded magnets from sintered Fe-2%P alloy - Air-gap flux density
Fig. 19 — Machine simulation with rotor of embedded magnets from sintered Fe-2%P alloy - Air-gap flux density
Fig. 20 - Machine simulation with rotor of embedded magnets from sintered Fe-2%P alloy - Flux lines in the longitudinal plane of the machine
Fig. 20 - Machine simulation with rotor of embedded magnets from sintered Fe-2%P alloy - Flux lines in the longitudinal plane of the machine
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