Adrian Młot

Torque characteristics of a BLDC motor with multipolar excitation

Purpose – This paper deals with magnetic field calculations and model‐based prediction of electromagnetic torque pulsations in a brushless DC (BLDC) motor.Design/methodology/approach – The impact of a Halbach‐like magnetization and a multipolar excitation of permanent magnets are analysed. The measurement results from the prototype motors are well‐compared with those obtained from the model calculations. It is shown that the cogging torque in the motor with the multipolar excitation of permanent magnets is reduced six times as compared with the conventional BLDC motor.Findings – The proposed method provides high accuracy of the analysis of coupled electromagnetic phenomena. The comparison between measured and calculated values of electromagnetic torque, cogging torque and EMF shows a very good agreement.Practical implications – Reduction of the machine cogging torque is essential for practical applications of DC motors, in particular in the robotics industry.Originality/value – This paper shows that multi...

Influence of an end-winding size on proximity losses in a high-speed PM synchronous motor

This paper deals with AC winding loss including proximity loss investigation in a high-speed permanent magnet (PM) machine for traction applications. The research is focused on the end-winding effects that have not been widely reported in the literature. The calculated results confirm that the end-winding copper loss can significantly affect the eddy-current loss within copper and it must be taken into account to provide reasonable prediction of total losses. A three-dimensional (3D) finite element analysis (FEA) is employed to evaluate and identify the end-winding contribution into the overall winding power loss generated. To explain how much the power loss may change due to dimensions and size of end-winding, the parameterized 3D FE models are investigated. In this study, the results clearly demonstrate that the size of end-winding has influence on the winding resistance and, consequently, the power loss in the AC operation. The theoretical prediction of the losses within the armature of the high-speed permanent magnet synchronous machine (PMSM) is validated experimentally on a segmented stator.

Investigation of End Winding Proximity Losses in a High-Speed PM Machine

This paper presents three- and two-dimensional finite element analyses (2D, 3D FEA) of the proximity losses in brushless AC permanent magnet motor with concentrated windings operating at high speed. The proximity effect only occurs if the examined conductor is penetrated by an external magnetic field, which is caused by adjacent conductor currents. To reduce the proximity effect several alternative winding layouts including rectangular wires are used. The calculated results of the eddy current losses within end-winding regions are significant and must be considered in the design of stator windings. 3D calculations are compared with 2D ones to show the behaviour of the eddy-current into the conductors and also compared with respect to the power loss and AC resistance. The calculations are in a good agreement with measurements on a prototype high-speed motor.

Electromagnetic Review of Rotor/Stator Misalignment in Permanent Magnet Axial Flux Motor

This paper presents the findings of a finite element analysis (FEA) investigation into the effect of rotor/stator misalignment on motor performance in a single rotor, dual stator, axial flux electric motor (AFM). Results obtained from the FEA are in good agreement with experimental measurements giving confidence in the use of the model. The results are useful to machine designers who wish to determine the sensitivity of rotor/stator misalignment, due to assembly errors or tolerance stack on machine performance. Axial offset of the rotor in the air gap is found to cause unbalanced axial forces on the rotor of up to 1400 N. The difference in iron loss between stators increased by 17 and 40% at high speed under open- and short-circuit conditions, respectively. Conversely, angular offset between the two stators was found to have little impact on unbalanced rotor forces and iron loss but a relatively large impact on recirculating currents within the machine which lead to uneven heating of the two stators. For an angular offset of 10 elec. deg. a recirculating current of 93 A was found for a phase current of 175 A. Torque ripple was found to decrease from 8 to 6%.

A single-phase slotless axial-flux low-power generator with ferrite magnets

The design and development of an axial-flux ferrite magnet slotless generator for use in a small-scale wind turbine is described. The 4/4-pole single-phase machine is designed for simplicity and ease of manufacture and it consists of one slotless stator disc. The generator produces approx. 12 W at 1000 rpm with electrical efficiency of up to 46%. Because the efficiency of the machine is important, the power curve characteristics and voltage produced by the generator are investigated. The presented generator should generate sufficient output DC voltage to charge 4 to 5 batteries of 12 volt each. Finally, the finite element (FE) results are compared with measurements on a prototype. The calculated values coincide to a strong degree with the experimental results.

Analysis of integral parameters in a single-phase slotless axial-flux machine used in small wind turbines

Analysis of integral parameters in a single-phase slotless axial-flux machine used in small wind turbines