This study proposes an improved decoupled model of mutually coupled dual-channel switched reluctance machine (DCSRM) based on the equivalent inductance and flux linkage characteristics that consider magnetic saturation in dual-channel operation (DCO) mode. A three-dimensional finite-element analysis (FEA) is used to calculate the static phase equivalent inductance of DCSRM for the simultaneous two-phase excitation with consideration of saturation. And an indirect experimental test is performed to measure the equivalent flux linkage under the simultaneous two-phase excitation and compared with the FEA results. In this improved decoupled model, the phase equivalent inductances and flux linkages in each channel are independent to each other and separately expressed as a function of rotor position and their own phase current. The static magnetic characteristics, details of modelling procedure and performances prediction for the DCSRM under DCO mode without and with consideration of saturation are compared. Finally, an experimental set-up for a 12/8 DCSRM drive system based on dSPACE is built and the simulation and experimental results are compared, which verifies high accuracy of this improved modelling method.

The study discusses development, implementation and performance of carrier-based pulse-width modulation (PWM) techniques for an asymmetrical six-phase open-end winding drive supplied by two two-level six-phase voltage source inverters (VSIs). The VSIs are fed from two equal and mutually isolated dc voltage sources, so that the same performance as with a three-level VSI in single-sided supply mode can be achieved. The considered modulation techniques are the in-phase disposition (PD-PWM) and the alternate phase opposition disposition, which are both classified as level-shifted PWM methods, and the phase-shifted PWM method. The performance is studied and compared using computer simulations and experiments undertaken on a laboratory prototype. It is shown that, in contrast to the three-phase and five-phase cases, the PD-PWM method does not offer the best performance.

Accurate measurement of power losses in high-efficiency devices is difficult. Measurement standards for industrial converters and complete electric drives, including both motors and converters, will come into effect soon, and measurement methods for these devices should be included. In the calorimetric method, the power losses are measured directly. However, the calorimeters presented previously are mainly tailored systems, and therefore, they typically have very complicated constructions. Hence, their applicability to the evaluation of general electric drives is limited. A functional calorimetric measurement concept is suggested in this study for power losses up to 2 kW. Such a power loss can be applied with present-day power electronic converters up to 110 kW. The construction of the concept is simple and lightweight. It does not require a complex structure or a large area in the measurement site. The concept is scalable and duplicable for different sizes. Different devices with different cablings can be measured without any problems. The combined standard heat loss measurement uncertainty for the calorimeter is ±0.4%.

This study presents a line-start permanent-magnet motor with high synchronisation capability using a slotted solid rotor. With slotted solid rotors, a much better magnetic flux and current penetration into the rotor is achieved. Moreover with additional magnetic flux penetration into rotor core, the motor slip decreases and electromagnetic torque near synchronous speed will increase. Consequently, the proposed motor can reach synchronous speed under higher load torques and inertias. Two-dimensional finite-element method has been implemented in order to confirm this new idea. Finally, a four-pole, 250 V, 1500 rpm, 1050 W, three-phase synchronous motor with slotted solid rotor is designed and prototyped to experimentally validate the capabilities of the proposed motor.

Pole-changing of line-start permanent magnet (LSPM) motors at start-up eliminates all their drawbacks such as poor starting torque, vibration at start-up and synchronisation problems. In addition, by using this method almost all the inherent limitations in the design parameters of line-start motors such as rotor resistance, permanent magnet strength and mechanical stress influenced by pulsating torques are alleviated. Therefore there is no need to compromise between the motor parameters. In this study, the design procedure of these motors is investigated and a high-performance motor based on the pole-changing starting-method is designed and fabricated. Next, the possibility and advantages of replacing laminated cage-bar rotors with solid rotors are investigated for pole-changing LSPM motors. Then, simulations are done by the two-dimensional finite element method and finally, the experimental results are presented. The good agreement between simulation and experimental results validates the theoretical method and also the new design.

The study presents a design-based computational procedure for determining the performance of a single-phase two-winding self-excited induction generator (SEIG) taking the machine design details as the input data. The magnetisation characteristic that forms the basis of analysis is obtained using the B–H curve of the core material and by employing an appropriate curve-fitting/regression technique that leads to obtain V _g–I _m variation from which V _g–X _m variation can be derived. The predicted parameters and performance characteristics of a single-phase SEIG are compared with the corresponding experimental results. This procedure can be a powerful tool for improved design of such machines. Effects of variation of typical design parameters on performance are presented to demonstrate its utility.

Many control schemes have been proposed for induction motors, which are in themselves highly complex non-linear and sometimes internally unstable systems. One of the most accurate control schemes is encodered rotor flux orientated vector control. The advantages and disadvantages of this control are well known and several variations, or reduced vector schemes, have been proposed. This study introduces an improved encoderless scalar, or approximated vector, control method for induction machines which can be applied to general purpose applications that do not require the most precise control. The proposed method overcomes practical difficulties and is suitable for industrial applications. The slip compensated stator flux linkage oriented scheme proposed in this study does not require flux estimation or a speed sensor, only requiring nameplate data, stator current and stator resistance measurement, which can easily be determined at start-up. Simulation and experimental investigations including field weakening operation and the effect of stator resistance variation demonstrate the improved performance of the new scheme compared to previous open loop V/Hz and stator resistive compensated schemes especially at low rotor speeds.

The on-load tap changing transformers have been widely used for their ability to maintain output voltages at desired levels despite the load or voltage changes in the ac mains. However, they present several disadvantages such as slow response, high-maintenance cost and discontinuous voltage regulation. This study proposes a novel on-load voltage regulator based on electronic power transformer (OLVR-EPT) to eliminate these drawbacks. By injecting an appropriate voltage component to traditional power transformer windings through EPT output stage, the resultant load voltage can be maintained at the desired value. There are no tap-changers anymore, so the voltage regulation is fast and continuous. Two sample schemes of OLVR-EPT are given and corresponding control method is developed in this study. The simulation and experimental results demonstrate that OLVR-EPT is able to maintain load voltages at the desired value effectively.

This study addresses the problem of detection and isolation of open-switch faults in voltage source inverters by processing the stator current measurements. First, the resulting post-fault trajectories for the stator currents are analytically derived for single and concurrent faults (21 classes) by using Fourier series. This analysis motivated the proposed approach, which is based on the resulting pattern of the stator currents in the dq-frame after a fault, where a histogram of the trajectory is calculated by dividing the plane in 24 equally spaced sectors. From the calculated histogram, a distinctive signature is associated to each fault trajectory in the dq-plane. Single and double faults in the power semi-conductors are analysed that all provide linearly independent signatures for fault isolation. The proposed isolation methodology is independent of the load torque (system disturbance), supply frequency and only requires the information of the stator currents. Furthermore, since the isolation stage is focused on the angle of the current trajectories in the dq-plane, open- and closed-loop configurations of a variable speed drive can be simultaneously handled. Experimental results with a test bench of 3/4 HP induction motor under single and concurrent faults validated the proposed methodology.

This study proposes a new design solution for static eccentricity in axial flux induction motors (AFIMs). There are two definitions for static eccentricity in AFIMs. In the first approach, that is, commonly used for double-side machines, the rotor axis does not coincide with the stator bore but rotor rotates around its own shaft. So, the air-gap of motor is not uniform. Usually, in single stator–single rotor arrangement the rotor integrates with rotating parts of mechanical load. So, when static eccentricity occurs, air-gap length remains uniform. Rotor axis remains parallel with stator axis whereas it does not coincide with the stator bore. Based on the authors’ knowledge, the latter approach has not been considered before. Therefore in this study a new definition for static eccentricity factor in direct drive is presented. Also, an optimisation is done to decrease the effect of static eccentricity on motor performance. The mathematical model of studied motor in transient and steady state is used based on d–q axis theory. In particular, the proposed model considers the effect of core saturation, and both approaches for modelling static eccentricity. Finally, studied motor is constructed and tested. All parameters of studied motor are calculated based on experimental measurements.