Mid Sweden University

This paper presents an experimental investigation on switching transients in a submodule of a cascaded H-bridge converter with the aim of investigating effects of direct integration of supercapacitor modules in switching converters. Departing from simulation studies focusing on overvoltage transients and effects from the Equivalent Series Inductance of the supercapacitor module. A passive absorption circuit is introduced to mitigate the transients on supercapacitor and switching components. The simulations are compared to experimental results on a submodule prototype. An operating point of the submodule corresponding to an output power of 6.2kW is investigated in a double pulse test. The experimental results show that effects of the series inductance across the switches are mitigated. The relationship between the equivalent series inductance of the supercapacitor and the rate of change of current is identified as causing overvoltages across the supercapacitor. Methods to handle the rate of change of current and high frequency voltage ripple across switches are suggested.

Traction drive applications demand high power density motors with a good stator cooling design. We propose a novel multi-phase winding for a 48 V traction drive design having identical preformed hollow copper conductors with in-conductor direct cooling capability. This paper studies the cooling performance of an individual conductor phase using either EGW50/50 or water as coolant. Analytical calculations and experiments are conducted on a straight conductor of the same length using 20°C water as coolant. The results are then cross verified with those from the FEM simulations to validate the simulation setup. Then a final simulation is conducted at a current of 700A and a current density of 49.5 A/mm 2 on the preformed conductor using 65 CEGW50/50 as coolant at a pressure of 140kPa. The results highlight the exceptional performance of the cooling design which enables a power dissipation of 71OW at a maximum conductor temperature rise of only 56. 9 C. 

A high copper fill factor allows reducing the resistive losses responsible for more than 50 % of the losses in today's most commonly used electrical motors. Single-turn windings achieve a copper fill factor close to one. Furthermore, they do not suffer from turn to turn faults and provide a low thermal resistance between winding and stator. The reduced EMF of single-turn winding configurations promotes the use of extra-low voltage high current MOSFETs. Rapid development of these MOSFETs allows reversing common design principles to explore new applications, such as battery electric traction drives. This paper presents a 2.5 V 1 kW MOSFET driven 13-phase permanent magnet DC motor with a single-turn winding configuration. The motor prototype with a copper fill factor of 0.84 was tested with continuous drive currents up to 600 A. The measured torque-efficiency map shows that such a high-current concept with voltages below 60 V is feasible using today's extremely low-voltage high current semiconductors. Due to the rapid development of such switches, there is great potential in this concept for further improvements. This work presents a small-scale version of the high-current drive, which is part of the development of an extra-low voltage traction drive concept. 

Paper presents new idea of modelling the magnetic hysteresis in the Jiles-Atherton model. Presented approach considers physical principles of magnetisation process and main assumptions of Jiles-Atherton model. As a result modified differential equation stating the model was proposed. This equation was verified on the base of magnetic hysteresis loops of non grain oriented electrical steel. Presented results indicate, that proposed approach to modelling the magnetic hysteresis loops well correspond with results of experimental measurements. 

Jiles-Atherton model is one of the most advanced and most popular models of magnetic hysteresis loop. However, this model is considering different physical phenomena and computational issues. As a result, cross-validation of the results of modelling performed by different authors became difficult. For this reason, the open-source MATLAB/OCTAVE based implementation of Jiles-Atherton model was developed. Proposed implementation covers isotropic model of magnetic hysteresis loops as well as uniaxial and grain oriented electrical steel anisotropy. Moreover, the corrections proposed by Venkataraman together with different approaches to derivative of the anhysteretic magnetization are considered. Developed library is freely available together with the examples of magnetic hysteresis loops. As a result, it can be the base for further development of Jiles-Atherton model for better understanding of magnetization process as well as modelling the inductive components.

The present invention relates to a torque sensor (1) comprising a body (2), at least one airtight chamber (3) provided in the body, a pressure sensor (4) measuring 1 the pressure in said at least one airtight chamber, and a pressure to torque converter (5) connected with the pressure sensor. Each airtight chamber is arranged to change its volume when the body is subjected to a torque, wherein the volume change causes a change of pressure of the enclosed air in the airtight chamber. The change of pressure is detected and converted to the corresponding torque.

This paper presents a torque sensor design based on a differential pressure measurement, focusing on thermal stability. The sensor utilizes the principle of measuring the differential volumetric strain due to the applied torque. The proposed design of the sensor is an improvement to the previous design of the sensor. Both the previous design and the improved design are discussed in terms of thermal stability. Comprehensive thermal simulations are conducted on the design in order to compare the thermal stability and performance of the sensors. Based on the presented results it is shown that prosed design of the sensor can achieve at least 99.61% better stability then the previous design. The range of the sensor is +/- 150N.m. Furthermore, it is also concluded that the new design also improves on the manufacturability, ease of integration and overall size of the sensor.

This paper proposes a torque sensor based on the differential air pressure measurement method using the volumetric strain of a mechanical sensing structure. A model of the measurement system based on the differential air pressure from the volumetric strain of the mechanical sensing structure is proposed and theoretically discussed. The error sources are identified and an error propagation model is presented for the proposed torque measurement method. Considering these error sources, a prototype torque sensor is presented as a case study for the method verification. Both the mechanical and readout electronics designs are discussed and analyzed. The mechanical sensitivity, resolution, and maximum stresses are analyzed using finite-element modeling. Based on the results from the simulation, a prototype torque sensor is manufactured and experimentally verified using a readout electronics design. For verification, the sensor prototype is measured under static torque to have a sensitivity of 0.04272V/N. m and a range of +/- 117N . m. Compared with the nominal mechanical sensitivity result from the FEM simulation, this measured sensitivity has a difference less than 6%. The noise analysis of the designed readout electronics shows that the resolution of 0.006% can be achieved with this design. Furthermore, hysteresis analysis shows an error of 0.012% of full scale. From these results, it is also shown that the actual performance of the sensor is mainly limited by the differential pressure sensor and the readout electronics design and is not by the mechanical design of the sensor.

This paper presents an experimental comparative analysis of a torque measurement method based on volumetric strain, utilizing a prototype torque sensor design is compared to a reference high performance torque sensor. A brief description of the background work of the numerical analysis of the method is also discussed as well as the readout electronics design. Based on the simulations and readout electronics analysis it is concluded that the sensor has a mechanical range of ±300 N·m. The manufacturing details of the prototype torque sensor are also discussed. A test setup is used to place the two torque sensors in line, to allow comparison for which a high performance conventional off-the-shelf torque sensor is selected. The experiments show that the proposed method of torque measurement can be fully implemented and used to measure torque with higher response time, resolution and wider range. Furthermore, future work is proposed to fully characterize the sensor over the full range using a reference setup rather than a torque sensor, as the available conventional sensors cannot be used to characterize the prototype torque sensor in full range with higher performance than the sensor itself.

Rapid development of extremely-low voltage high current MOSFETs allows reversing common design principles to explore new applications, such as battery powered traction drives. This enables the usage of multi-phase single-turn stator windings which can achieve a copper fill factor close to one. This paper briefly describes the proposed 2V, 1.1kW MOSFET commutated 13-phase permanent magnet DC motor and presents the efficiency and resistive loss measurements of the first prototype. The motor was successfully run with drive currents up to 520 A. Most of the obtained losses were resistive contact losses due to the flexible winding connections, less than 6% are dedicated to the MOSFETs. The results show that such a high current drive system is feasible and has great potential for further improvements, which is supported by the rapid development of extremely-low voltage high current semiconductors.