Arda Tuysuz

Modeling and Comparison of Machine and Converter Losses for PWM and PAM in High-Speed Drives

For variable-speed drives, the interaction of the machine and the converter is becoming increasingly important, especially for high-speed applications, mainly due to the effect of the converter modulation on the machine losses. The allocation of the losses to different components of the drive system needs to be known in order to choose the ideal machine and modulation combination. In this paper, individual models are introduced for calculating the rotor, copper, and core losses of the machine as well as the inverter losses, taking the modulation type into account. These models are developed by considering two typical high-speed permanent-magnet synchronous motor topologies (slotted and slotless machines) driven by pulse-amplitude modulation (PAM) and pulsewidth modulation (PWM) converters. The models are applied to two off-the-shelf machines and a converter operating with either PAM or PWM. The test bench used to experimentally verify the models is also described, and the model results are compared to the measurements. The results show that PAM produces a higher overall efficiency for the high-speed machines considered in this paper. However, PWM can be used to move the losses from the rotor to the converter at the expense of decreasing the overall drive efficiency. The possible benefits of these results are discussed.

Performance Comparison of a GaN GIT and a Si IGBT for High-Speed Drive Applications

GaN power switches enable better switching characteristics compared to state-of-the-art power transistors that are widely used today. Due to their lower switching losses, GaN switches may lead to new horizons in key application areas of power electronics such as photovoltaic converters, high-speed electrical drives and contactless power transfer. However, this technology has not yet diffused fully into the industry. Therefore, today only limited experimental data is available on those switches. In this paper, a synchronous buck converter is designed using two 600 V, 15 A GaN GIT switches developed by Panasonic. Guidelines for an optimum PCB layout are given. Both electrical and calorimetric power loss measurements are shown. Finally, a comparison is made between the GIT and a similarly rated Si IGBT for high-speed electrical drive applications where the higher switching frequencies enabled by the use of GaN is shown to reduce the rotor losses in two typical types (slotted and slotless stator) of high-speed permanent-magnet electric machines.

A Novel Motor Topology for High-Speed Micro-Machining Applications

In this paper, a novel motor topology (lateral stator machine) is proposed for various drilling applications where the space in the tool head is limited. The stator of the motor grows in one lateral direction, allowing for a compact direct drive design. Finite-element analysis (FEA) is carried out and the machine design is optimized for the specifications of a high-speed micro-machining spindle which is given as an example. The design procedure for those specifications is described in detail, where the torque is maximized while considering the space limitations and the loss constraints at the critical operating points. The construction of a lateral stator machine merged into a test bench is also described. The test bench is used for measuring the standstill torque of the machine in a configuration without bearings, such that only the electromagnetic torque is measured without any friction effects from the bearings. Moreover, the test bench can be modified to measure the no-load losses and separate the mechanical and electromagnetic components of it. Although described on a lateral stator machine, the measurement methodology of this paper can be applied to any electrical machine. Finally, measurement results are given and the design procedure is verified.

Increase of tape wound core losses due to interlamination short circuits and orthogonal flux components

High performance laminated core materials are nowadays used in several different applications, from some Watts to some Megawatts and from some tens of Hertz to some hundreds of Kilohertz. Cutting laminated or tape wound cores in order to obtain a desired geometry results in higher core losses mainly due to the introduction of short circuits between layers of magnetic material and also due to the flux which is perpendicular to the layer plane as given for the fringing field of inductors or the stray field of transformers. This paper verifies the influence of some machining methods on the increase of core losses and shows an approach to keep the effect minimized. Furthermore, the importance of considering core losses due to perpendicular flux is verified for a cut core inductor and a transformer arrangement.

Novel miniature motors with lateral stator for a wide torque and speed range

For various drilling applications where the space in the tool head is limited, two motor topologies with the stator outsourced from the head are proposed, allowing for compact design and direct drive. In order to meet the high torque requirements at low speed and operate at high speed up to 200 000 rpm a finite element analysis (FEA) is carried out and the machine design is optimized for maximum torque while considering the space limitations and the loss constraints at the critical operating points. As an example, for the specifications of a high-speed micro-machining spindle covering a wide application range, FEA results are presented. Moreover, a torque ripple compensation method based on phase current profiles obtained from FEA is proposed to eliminate the torque ripple caused by the stator asymmetry and slotting.

Analysis and power scaling of a single-sided linear induction machine for energy harvesting

Although Single-Sided Linear Induction Machines (SLIMs) have been analyzed and tested intensively as prime movers for different applications in literature, their application for energy harvesting has not been studied rigorously. This paper investigates the use of SLIMs for watt-range energy harvesting from a moving steel body with smooth surface (solid steel secondary) in order to supply control electronics and actuators in industrial environments. Based on a brief study of the electromagnetic relations in the air gap and the solid steel secondary, a power scaling law as function of the geometric parameters and stator current is derived. The scaling law is verified with two-dimensional Finite Element Method (2-D FEM) simulations and measurements on a test setup. The proposed scaling law is an effective tool for estimating the performance of a SLIM for contactless energy harvesting in emerging industry and consumer applications.

Novel signal injection methods for high speed self-sensing electrical drives

This paper proposes a novel self-sensing method for high speed electrical drives. Signal injection, measurement, filtering and demodulation stages are built in dedicated hardware, reducing the computational effort for the signal processor and removing any need to modify the drive inverter operation. Differential measurements make this method applicable for even very low saliency machines such as slotless permanent magnet machines. Different variations of the proposed method are explained on two different machine examples. Experimental results verify the applicability of the proposed method.

Analysis of a watt-range contactless electromechanical energy harvester facing a moving conductive surface

A watt-range contactless electromechanical energy harvester based on the interaction of a rotating permanent magnet wheel with a moving conductive surface is analyzed, modeled and optimized. The extracted models are verified with two-dimensional (2-D) finite-element-method (FEM) simulations and measurement results. Finally, a ρη-Pareto optimization indicates a power density of the harvester wheel in the range of 2 W/cm3 for surface speeds of 10m/s and an air gap of 3 mm.

Gate signal jitter elimination and noise shaping modulation for high-SNR Class-D power amplifiers

Two important aspects of switched-mode (Class-D) amplifiers providing a high signal to noise ratio (SNR) for mechatronic applications are investigated. Signal jitter is common in digital systems and introduces noise, leading to a deterioration of the SNR. Hence, a jitter elimination technique for the transistor gate signals in power electronic converters is presented and verified. Jitter is reduced tenfold as compared to traditional approaches to values of 25 ps at the output of the power stage. Additionally, digital modulators used for the generation of the switch control signals can only achieve a limited resolution (and hence, limited SNR) due to timing constraints in digital circuits. Consequently, a specialized modulator structure based on noise shaping is presented and optimized which enables the creation of high-resolution switch control signals. This, together with the jitter reduction circuit, enables half-bridge output voltage SNR values of more than 100dB in an open-loop system.

Novel contactless axial-flux permanent-magnet electromechanical energy harvester

This paper proposes a novel type of watt-range permanent-magnet energy harvester, which harvests energy from a moving conductive body or surface without mechanical contact, as its operation is purely based on eddy-current coupling. The harvesters main advantage over existing solutions is that it allows energy transfer over atypically large (2 ... 15 mm) air gaps, which are unavoidable in certain industrial applications. The paper provides a detailed description of the systems operating principle, and elaborates its modeling using 3-D Finite-Element Method (FEM) analysis. Two prototypes are built and tested for verifying the models. A power of 2.42W is harvested from an aluminum surface moving with 10 m/s, over 12mm air gap using a prototype with ≈ 14 cm3 magnet volume. Moreover, the effects of the harvesters placement as well as the speed of the moving conductive surface on the maximum harvested power and the systems efficiency are analyzed, both with FEM simulations and measurements.