Field Weakening Operation of Slotless Permanent Magnet Machines using Stator Embedded Inductor

Abstract : This article presents a comprehensive design methodology to improve the field weakening (FW) operation of low inductance slotless permanent magnet synchronous machines (PMSMs). The proposed concept of using a stator embedded inductor integrated with the torque producing machine windings helps achieve a wide constant power speed range (CPSR) and a desired torque/speed characteristics. Key performance parameters including system efficiency and PWM induced current ripple are summarized for scenarios with and without the embedded inductor in the entire operating range using 2-D finite element analysis. The concept helps to achieve the desirable extended torque/speed range. It also helps to improve the efficiency beyond the base speed operation for a high speed, high power machine. In addition to achieving desired CPSR, this method also helps to reduce the PWM induced current ripple, short circuit current, and current ripple induced core losses. A slotless machine with the integrated embedded inductor has been designed following the proposed design guidelines to extend the CPSR, and a prototype motor has been built to validate the simulation results with the experimental results.

 EXISTING SYSTEM :

 ? The majority of existing papers referring to the analysis of wind energy systems, use simulation tools that are more focused on the detailed simulation of the control system rather than the machine. ? The geometric positioning of the nodal elements that model different regions of the machine, is established according to the existing main magnetic flux paths. ? The airgap meshing is controlled by the number of existing nodal elements at the stator–airgap border, and the rotor–airgap border. ? In the proposed strategy, the existing back-EMF and position estimator are used and no additional algorithm or specific voltage vector injection is required.

 DISADVANTAGE :

 ? A non-salient pole permanent magnet machine has low phase inductance due to higher effective airgap and has limited field weakening range. ? This problem is severe in slotless or coreless topology due to the low phase inductance. ? The output power decreases faster above the base speed compared to the slotted topology.However, a wide constant power range is essential for transportation applications. ? Therefore, the machine and power electronics have to be oversized to match the torque and speed specifications. ? One problem for the generality of the result is the dependence on the pole pitch which varies greatly depending on the size of the machine.

 PROPOSED SYSTEM :

 • The proposed method can detect both mechanical and electrical faults. However, two-pole machines provide an extra challenge, as they have the same mechanical and electrical frequency. • Because motor restarting is generally practiced at medium and high speeds, a restarting strategy for back-EMF-based sensorless PMSM drives is proposed in this paper. • These techniques can be used in future works as auxiliary tools to complement the fault diagnosis by using the proposed methodology, being not in the scope of the present work. • The main objective was to point them out and show how they have been approached. Moreover, the influence of saturation and power factor in SG fault detection is not addressed, being proposed for future works.

 ADVANTAGE :

 ? Permanent magnet machines are increasingly used in different applications including EV, HEV, UAV, drones, solar powered aircraft, flying cars, servo, electric power steering (EPS), and compressors due to its superior performance compared to other machine topologies. ? A series compensation technique using two inverters with distributed controllers to improve the flux weakening performance of an interior permanent magnet machine is presented in . ? The embedded inductor effectively increases the d-axis inductance and improves the FW performance. The design constraints and steps to achieve the optimal CPSR or extended FW range in a slotless motor is presented. ? Hence, Halbach increases the torque per inertia and improves the dynamic performance as well.