Zlatko Kolondzovski

Power Limits of High-Speed Permanent-Magnet Electrical Machines for Compressor Applications

The maximum-power limits for high-speed permanent-magnet (PM) electrical machines for air compressor applications are determined in the speed range 20000-100000 r/min. For this purpose, five PM machines are designed and the electromagnetic, thermal, and mechanical designs of each machine are simultaneously performed. The critical values of the thermal and mechanical constraints are considered in order to obtain the maximum powers of the electrical machines. The electromagnetic losses generated in the machine are the output parameters of the electromagnetic design and input parameters for the thermal design. The thermal design is performed using a multiphysics method, which couples computational-fluid-dynamics equations with heat-transfer equations. The mechanical design considers the retention of the rotor elements against the huge centrifugal forces that arise during the high-speed operation and also the rotor dynamics properties of the rotor. The reliability of these design techniques is experimentally validated in the paper. The obtained maximum-power limit defines the speed-power region, in which the high-speed PM electrical machines intended for compressor applications can have a safe operation.

Determination of critical thermal operations for high‐speed permanent magnet electrical machines

Purpose – The thermal design of high‐speed electrical machines is a greater challenge in comparison with conventional electrical machines. When designing the machine, the calculated temperatures in all parts should be lower than their critical temperatures. This paper aims to perform thermal analysis for different rotor types according to the level of shield from eddy currents in order to achieve a safe thermal design of the machine.Design/methodology/approach – The machine under study in the paper is a high‐speed permanent magnet (PM) motor designed for speed n=31,500 rpm and power P=130 kW. A thermal‐network method was used for thermal analysis of the machine.Findings – The minimum value of the coolant flow in the air gap that provides an effective cooling of the machine was estimated. The coolant itself is not able to provide an effective cooling of the magnets if they are not shielded from eddy currents.Research limitations/implications – The results are obtained only by the thermal‐network method. Nu...

Numerical modelling of the coolant flow in a high-speed electrical machine

In the paper, a numerical modelling of the air-flow in a high-speed permanent-magnet electrical machine is presented. The method couples computational fluid dynamics and heat-transfer equations in order to estimate the turbulent and thermal properties of the flow. The machine under consideration is a high-speed PM motor that is designed for speed n = 31500 rpm and power P = 130 kW. The geometry of the fluid domain in this method is considered to be 2D axi-symmetric. At the end, results for the turbulent properties as well as for the temperature rises of the cooling fluid are presented.

Combined FE and Particle Swarm algorithm for optimization of high speed PM synchronous machine

Purpose – The purpose of this paper is to optimize the stator slot geometry of a high-speed electrical machine, which is used as an assist for a turbocharger. Meanwhile, the suitability of the Particle Swarm algorithm for such a problem is to be tested. Design/methodology/approach – The starting point of the optimization is an existing design, for which the Particle Swarm algorithm is applied in conjunction with the transient time-stepping 2D finite element method. Findings – It is found that regardless of its stochastic nature, the Particle Swarm work well for the optimization of electrical machines. The optimized design resulted in an increase of the slot area and increase of the iron loss, which was compensated by a dramatic decrease in the Joule losses. Research limitations/implications – The optimization was concentrated on the stator design whereas the rotor dimensioning was carried out withing the compressor and turbine design. Originality/value – A turbocharger with electric assist is designed opt...

FEM coupling for transient performance analysis of a salient poles synchronous generator

In the paper the full performance analysis of a salient poles synchronous generator (SPSG) is presented. The focus is put on the simulation of transient characteristics in the case of three-phase bolted short circuit at the generator terminals. The analysis is based on the combined solution of the magnetic field equations and the circuit equations of windings. The equations are elaborated by the finite element method (FEM) and the field solution is obtained by using of the time-stepping approach.