Nikita Uzhegov

Hysteresis Losses in Sintered NdFeB Permanent Magnets in Rotating Electrical Machines

Permanent magnet (PM) materials are nowadays widely used in the electrical machine manufacturing industry. The eddy-current loss models of PMs used in electrical machines are frequently discussed in research papers. In magnetic steel materials we have, in addition to eddy-current losses, there are hysteresis losses when alternating current or a rotating flux travels through the material. Should a similar phenomenon be also taken into account in calculating the losses of PMs? Every now and then, authors seem to assume that some significant hysteresis losses are present in rotating machine PMs. This paper studies the mechanisms of possible hysteresis losses in PMs and their role in PMs when used in rotating electrical machines.

Multidisciplinary Design Process of a 6-Slot 2-Pole High-Speed Permanent-Magnet Synchronous Machine

High-speed permanent-magnet synchronous machines (HS PMSMs) are a popular topology among modern electrical machines. Suitable applications for such machines are low-power vacuum pumps, compressors, and chillers. This paper describes a systematic design methodology for an HS PMSM using two case studies. The design process for such high-speed (HS) machines is multidisciplinary and highly iterative due to the complex interaction of the many design variables involved. Consequently, no single optimum solution exists, and multiple possible solutions can meet the customer requirements. Practical solutions should be within acceptable thermal limits, should be energy-efficient, and should be rigid enough to withstand the forces exerted during operation. The proposed design flow is divided into steps that are presented in this paper in the form of a flowchart with emphasis on mechanical aspects. Each step represents a task for a thermal, mechanical, or electrical engineer. The features of each step and the prerequisites for moving to the next step are discussed. The described methodology was implemented in the design of two HS PMSMs. The output performance results of the design flow are compared with measured results of the prototypes. The design process described in this paper provides a straightforward procedure for the multidisciplinary design of HS permanent magnet electrical machines.

Loss minimization in high-speed Permanent Magnet Synchronous Machines with tooth-coil windings

This paper investigates loss minimization in high-speed, low-power Permanent Magnet Synchronous Machines (PMSMs) with tooth-coil windings (TC-PMSMs). The influence of the main geometric parameters on the loss distribution is studied. Stator core and winding losses as well as rotor sleeve and permanent magnet (PM) losses are evaluated. The effect of the magnetic wedges on the loss distribution is examined. The machine working temperature and related PM demagnetization risks at the rated working point are presented for two- and three-phase short-circuits. The total losses of the designed PMSM are evaluated and a minimum total loss value is obtained.

Design limitations of 6-slot 2-pole high-speed permanent Magnet Synchronous machines with Tooth-Coil windings

Mechanical and electro-magnetic limitations of high-speed tooth-coil electrical machines having 6 slots and 2 poles are investigated. The paper analyses the performance of a designed high-speed Permanent Magnet Synchronous Generator with Tooth-Coil windings (TC-PMSM) with the topology mentioned. The generator nominal power is designed for 11 kW and nominal rotation speed is set to 31 200 rpm.

Factors affecting hysteresis loss risk in rotor-surface-magnet PMSMs

In early papers about Permanent Magnet Synchronous Machines (PMSMs) it was often stated that there are no rotor losses in PMSMs. Later, eddy current analyses for sintered permanent magnets (PMs) have been dominating the rotor loss analyses. However, in some designs also hysteresis losses can be possible in PMs. This paper uses 2D Finite Element Method (FEM) program and 2D slotless analytical model to show the main factors affecting the hysteresis loss emergence and the applicability limitations of the existing analytical approaches in evaluating the hysteresis loss. A Tooth Coil Winding PMSM prototype with external rotor topology is used in the analysis as a reference.

High-Speed Electrical Machine with Active Magnetic Bearing System Optimization

High-speed (HS) electrical machines provide high system efficiency, compact design, and low material consumption. Active magnetic bearings (AMBs) bring additional benefits to the HS system, such as elimination of the friction losses, reduced wear and maintenance, and a built-in monitoring system. HS drivetrains are usually designed for specific applications and require a high level of integration. This paper describes a design method of the HS electrical machine supported by AMBs, considering their mutual influence on the system performance. The optimization procedure, which takes into account both the electrical machine and bearing designs, is developed. The optimization is based on a multiobjective genetic algorithm. The selected optimization parameters include the AMB and machine dimensions. The optimization objectives cover the electrical machine performance and the rotordynamics. The results of the proposed optimization algorithm are implemented in the constructed 350-kW, 15 000-r/min induction machine with a solid rotor supported by AMBs. The prototype tests verify the design and optimization results.

Comparison of high-speed electrical motors for a turbo circulator application

This paper introduces the analysis of three different electrical machine topologies for a special application. The machines are designed to operate with 6 kW output at 120 000 rpm. The design aspects of one squirrel cage induction motor and two permanent magnet machines are presented. The comparison of the machines include electromagnetic, thermal and mechanical analyses. The advantages and drawbacks of each topology under consideration are drawn. The comparison structure helps in selecting the suitable electrical machine topology also for other High-Speed (HS) applications.

An analysis of the 6-slot 2-pole high-speed permanent magnet synchronous machines with tooth-coil windings

Two low-power High-Speed Permanent Magnet Synchronous Machines (HS PMSM) are reviewed. The powers and speeds of the machines are 3.5 kW at 45 000 rpm and 11 kW at 31 200 rpm. Both machines under consideration have 6 slots and 2 poles and they are both using Tooth-Coil (TC) windings also known as non-overlapping concentrated windings. The rotors of the discussed machines consist of the diametrically magnetized full cylindrical Permanent Magnet (PM) inside a retaining sleeve. The similarities and differences between these two machines are described and explained. The analysis of the air gap flux density, its harmonic content, and loss distribution in comparison with a Distributed Windings (DW) solution is presented with the example of an 11 kW machine. The analytical and numerical calculations are verified by the experimental data. Based on this analysis, conclusions will be drawn regarding the suitability of the implemented topology for a high-speed machinery.

Comparison of High-Speed Electrical Motors for a Turbo Circulator Application

This paper introduces the analysis of three different electrical machine topologies for a special application. The machines are designed to operate with 6 kW output at 120 000 rpm. The design aspects of one squirrel cage induction motor and two permanent magnet machines are presented. The comparison of the machines include electromagnetic, thermal and mechanical analyses. The advantages and drawbacks of each topology under consideration are drawn. The comparison structure helps in selecting the suitable electrical machine topology also for other High-Speed (HS) applications.

Design Aspects of High-Speed Electrical Machines With Active Magnetic Bearings for Compressor Applications

Two-stage oil-free centrifugal air compressors can bring significant advantages and open new market opportunities for compressor manufacturers. One of the core technologies behind this compressor type is the high-speed electrical machine supported by active magnetic bearings. In this paper, the requirements set by the compressor on the electrical machine design are presented. The design solutions aimed to satisfy these requirements are discussed. Two case studies illustrate possible design approaches for the target application with examples of a 120-kW, 60 000-r/min induction machine with a solid rotor and a 225-kW, 50 000-r/min permanent-magnet synchronous machine (PMSM) with a full cylindrical magnet. The system design and simulation results are confirmed by measurements of a PMSM prototype.