Hanafy Mahmoud

Eccentricity in Synchronous Reluctance Motors—Part I: Analytical and Finite-Element Models

In recent years, there is a growing interest for synchronous reluctance machines. This is due to their high torque density, flux-weakening operation capability, and high fault-tolerance capability. This paper deals with the analysis of a synchronous reluctance machine when eccentricity occurs. Both static and dynamic eccentricity are considered. An analytical model to predict the machine performance is described. As an example, a four-pole reluctance machine is analyzed, considering single, as well as multi flux-barriers per pole. The finite-element analysis confirms the results achieved by means of the proposed analytical model.

An Analytical Approach to Design the PM in PMAREL Motors Robust Toward the Demagnetization

In the permanent magnet (PM)-assisted reluctance motors, low-energy PM, such as Ferrite PM, is used to get a cheap rotor. As far as the design choices are concerned, the PM width has to be selected so as to achieve the desired air-gap flux density at no-load condition and the PM thickness has to be selected to avoid the demagnetization of the PM under full-load conditions. This paper presents a practical analytical approach to compute PM width and thickness according to a given air-gap flux density and stress on the PM itself. Two approaches based on a complete model and a simplified model are considered and compared. As an example, a 36-slot 4-pole machine is designed. Finite element analysis confirms the results achieved by means of both analytical analyses.

Eccentricity in Synchronous Reluctance Motors—Part II: Different Rotor Geometry and Stator Windings

Referring to the analysis of the impact of the eccentricity on a synchronous reluctance motor presented in the companion paper (Part I), a comparison is carried out between rotors with symmetric and asymmetric flux-barriers. As an example, a four-pole machine with one or two flux-barriers per pole is used. In addition, the analysis is also applied to motors with fractional-slot coil windings. Both single- and double-layer windings are considered. As an example, a six-slot four-pole machine with concentrated windings and 36-slot four-pole machine with distributed windings are compared. The analytical model which is proposed in Part I is used to predict the machine performance. A finite-element analysis confirms the results achieved by means of the analytical model.

Analytical comparison of synchronous reluctance and surface permanent magnet machines with rotor eccentricity

This paper deals with the unbalanced forces due to the rotor eccentricity. It describes two analytical models suitable for surface permanent magnet machine and synchronous reluctance machine, suitable to predict the flux density with a non-uniform air gap. The radial force on the rotor of the two machines is estimated in case of different rotor eccentricities, at no load and under load conditions. Both uniform and non-uniform eccentricity along the axial length of the machine are considered. For the purpose of comparing the two machine topologies, two 36-slot 4-pole machines are considered. The main geometrical dimensions are the same. Finite element analysis confirms the results achieved by means of both analytical models.

Magnetic field analytical computation in synchronous reluctance machines considering the iron saturation

This paper deals with an analytical model of REL motor considering the stator slotting effect and the magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air-gap to a lumped-parameter magnetic network. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model.

Comparison between synchronous reluctance and interior permanent magnet motors with eccentricity

This paper presents the finite element analysis for synchronous reluctance and interior permanent magnet machines with different eccentricity scenarios. Static and dynamic eccentricity cases are studied, as well as, a combination of them is also studied. Three different rotor structures are considered for both machines. This paper focuses on the computation of the unbalanced radial force acting on the rotor in all eccentricity scenarios. In addition, the radial forces acting on the rotor flux-barriers (i.e., in case of synchronous reluctance machine) or acting on magnets (i.e., in case of interior permanent magnet machine) are calculated. As an example, a 36-slots 4-pole machines with the same dimensions are compared. The comparison between the different rotor geometries is also carried out for all eccentricity cases.

Comparison between synchronous machines with eccentricity: Reluctance and Permanent Magnets

This paper deals with the finite element analysis of synchronous reluctance (REL), Permanent Magnet Assisted reluctance (PMAREL), and surface mounted permanent magnet (SPM) machines with different eccentricity cases, as static, dynamic, and mixed eccentricity. Different rotor geometries are considered for both REL and PMAREL machines. This paper focuses on the computation of the unbalanced radial force acting on the rotor in case of eccentricity. Moreover, the radial forces acting on the rotor parts bordered by the flux-barriers are calculated. For generality sake, this comparison is carried out at different levels of air-gap flux density. Therefore, different load angles, different permanent magnet (PM) types, and different number of poles are considered.

An improved analytical model of eccentric synchronous reluctance machines considering the iron saturation and slotting effect

This paper deals with an improved analytical model of Synchronous Reluctance (REL) machine with eccentricity. This model considers the magnetic saturation occurring in the different iron parts of the stator and the rotor. This saturation results from the actual B-H characteristic of the iron. In addition, the slotting effect is considered in the analytical model. The unbalanced magnetic force (UMF) on the rotor is accurately estimated. Furthermore, the impact on the estimated UMF due to the slotting effect and the magnetic saturation is studied. Both static and dynamic eccentricity cases are considered. As an example, 4 pole 36 slot REL motor with three flux-barriers per rotor pole is considered. FE analysis is carried out to confirm the results achieved by means of the improved analytical model.

An inverse approach for inter-turn fault detection in asynchronous machines using magnetic pendulous oscillation technique

In this paper, a coupled experimental-mathematical inverse problem based methodology for the detection of inter-turn faults in an asynchronous induction machine is presented. The fault detection is accomplished by interpreting well-defined measurements into the machine mathematical model. First, the studied machine is modeled by means of a dynamic state-space model in the abc reference frame. This model simulates the machine behavior under healthy and faulty cases in both transient and steady-state conditions. The signature of the inter-turn fault is captured using the magnetic pendulous oscillation technique. The proposed inverse problem is validated numerically and experimentally. The results show the robustness of the proposed scheme against the measurement noise.

Nonlinear Analytical Model of Eccentric Synchronous Reluctance Machines Considering the Iron Saturation and Slotting Effect

This paper deals with an improved analytical model of synchronous reluctance (REL) machine considering rotor eccentricity. This model considers the magnetic saturation in the iron parts of both the stator and the rotor. This saturation results from the actual B–H characteristic of the iron. In addition, the slotting effect is considered in the analytical model. The unbalanced magnetic force (UMF) on the rotor is accurately estimated. Furthermore, the impact on the estimated UMF due to the slotting effect and the magnetic saturation is studied. Both static and dynamic eccentricity cases are considered. As an example, a four-pole 36-slot REL motor with three flux-barriers per rotor pole is considered. Experimental measurements confirm the results achieved by means of both finite-element analysis and the improved analytical model.