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Nowadays, electronics has really flourished with the rapid progress in science and technology. Besides being light and efficient of the products, digitalization and faster speed are also required which make the problem of EMI, electromagnetic interference, become more serious. Newer power supplies using switching technology become smaller and smaller. However, they also produce EMI problems that need to be considered. In this thesis, we only address the conducted EMI. Generally, the noise is suppressed by adding a filter at the power-line end. Hence, the EMI filter plays an important role to the solution of conducted emission. The particular filter is related to the type of the conducted emission, including common-mode and differential-mode. As a result, it is a great help for an engineer to be able to separate the noise. There are several noise separators in the present days. We propose new separators, which are capable of detect common-mode and differential-mode separately. Our separators are low-cost, easily manufactured and are able to give exact noise readings without adjustment. Incorporating the known methods of filter design and combing programming measurement the filter design can be made automatic. One approach makes use of the spectrum analyzer, which is considered to be a relatively expensive instrument. We also propose another approach using oscilloscope. The time-domain measurement is performed and transformed into frequency domain using FFT. A realistic design example is shown to give satisfactory results.

Increasing power density of switch mode power supplies, by increasing their switching frequency has becoming a challenging obstacle for EMI mitigation. The passive EMI suppression technique has always been the primary solution to fulfill the EMC requirement in terms of conducted emission limits. However, the call for stringent power supplies specifications renders the passive techniques less desirable, due to their increasing size and power losses. In other words, the greater the power density of the converter, the bigger the passive filter. Other suppression techniques such as the spread spectrum frequency modulation (SSFM), and soft switching, prove to have less performance and much complex to implement. The active analog EMI filters provide the basic noise suppression technique; however, their performance is dramatically impeded at higher frequency. This solution requires an additional small size passive filter to complete the EMC spectrum for conducted emissions. Digital active filtering techniques offer advantages of flexibility, fewer external components and reduced overall size and power losses as compared to conventional passive filtering techniques. In this thesis DSP-based and FPGA-based EMI control techniques to mitigate the conducted emissions of switch mode power converters are proposed. These techniques are implemented in-lieu of the passive filtering techniques, by keeping equal or better performance. Moreover, these solutions can be configured as a stand-alone or integrated into the converter digital controller algorithm. Finally, the proposed solutions are implemented into three types of power converters, namely, a AC-DC power factor corrected converter, DC-AC micro-inverter for Photovoltaic application, and DC-DC for Electric Vehicle (EV) battery charger. Analytical, simulation and experimental results are provided to verify the proposed solutions. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-11-07 10:48:49.191

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This work presents the modeling and analysis of EMI and thermal performance for switch power supply by using the CAD tools. The methodology and design guidelines are developed. By using a boost PFC circuit as an example, an equivalent circuit model is built for EMI noise prediction and analysis. The parasitic elements of circuit layout and components are extracted analytically or by using CAD tools. Based on the model, circuit layout and magnetic component design are modified to minimize circuit EMI. EMI filter can be designed at an early stage without prototype implementation. In the second part, thermal analyses are conducted for the circuit by using the software Flotherm, which includes the mechanism of conduction, convection and radiation. Thermal models are built for the components. Thermal performance of the circuit and the temperature profile of components are predicted. Improved thermal management and winding arrangement are investigated to reduce temperature. In the third part, several circuit layouts and inductor design examples are checked from both the EMI and thermal point of view. Insightful information is obtained. / Master of Science

This works systematically presents various strategies to reduce both differential mode (DM) and common mode (CM) noise using a passive filter in a dc-fed motor drive. Following a standard approach a baseline filter is first designed to be used as reference to understand and compare the available filter topologies. Furthermore, it is used to analyze the grounding scheme of EMI filter and more specifically provide guidelines to ground single or multi stages filter. Finally, the baseline filter is investigated to recognize the possible solutions to minimize the size of the whole filter. It turns out that the CM choke and DM capacitors are the two main downsides to achieve a small EMI filter. Therefore, ideas are proposed to improve the CM choke by using other type of material such as nano crystalline core, different winding technique and new integrated method. A material comparison study is made between the common ferrite core and the nano crystalline core. Its advantages (high permeability and saturation flux density) and drawback (huge permeability drop) are analyzed thought multitudes of small and large signals tests. A novel integrated filter structure is addressed that maximizes the window area of the ferrite core and increases its leakage inductance by integrating both CM and DM inductances on the same core. Small- and large-signal experiments are conducted to verify the validity of the structure showing an effective size reduction and a good improvement at low and high frequencies. To conclude, a final filter version is proposed that reduce the volume of the baseline filter by three improve the performances in power tests. / Master of Science

With the development of power electronics, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues have become more and more important for both power converter designers and customers. This dissertation studies EMI noise emission characterization and modeling in power converters. A modular-terminal-behavioral (MTB) equivalent EMI noise source modeling approach is proposed. This work is the first to systematically develop a 3-terminal EMI noise source model for a switching phase-leg device module. Each module is modeled as pairs of equivalent noise current sources and source impedances. Although the proposed MTB modeling approach applies the linear circuit theory to a semiconductor switching device, which exhibits nonlinear behavior during switching transients, the analysis and experiments show that the nonlinearity has negligible practical effect on the modeling methodology. The validation range of the modeling methodology has been analyzed. One of the differences between the proposed MTB model and the other state-of-the-art models is that the MTB model characterizes and predicts the CM and DM noise simultaneously. The inseparable high-frequency CM and DM noise characteristics contributed by the source impedance and propagation path are analyzed. A comprehensive evaluation of different EMI noise source modeling approaches according to the criteria of accuracy, feasibility and generality has been presented. Results show that the MTB modeling approach is more accurate, feasible and general than other approaches. The modular and terminal characteristics of the MTB noise source model are verified in two more complicated cases. One example is the application of the MTB equivalent source model in a half-bridge AC converter with variable switching conditions. Although the MTB model is derived under a certain operating condition, the models under different conditions can be combined together to predict the EMI noise for the converter with variable switching conditions. Another example is the application of the MTB equivalent source model in multi-phase-leg converters. The EMI noise of a full-bridge converter is predicted based on the MTB equivalent source model of one phase-leg module. The implementation procedures and results for both applications are verified by the experiment. The applicability of the MTB model in different type of converters is discussed. Based on the MTB model, EMI noise management is explored. The parametric study based on the MTB model is demonstrated by selecting DC-link decoupling capacitors for voltage source converter (VSC). The EMI effect of a decoupling capacitor for a device s safe operation is analyzed, and this analysis shows the terminal characteristics of the MTB model. Both the EMI and voltage overshoot are predicted by the MTB model. A completed converter-level EMI model can be derived based on the noise source model and propagation path model. This model makes it possible to optimize the EMI filter design and study the EMI noise interactions between converters in a power conversion system. / Ph. D.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The UMR Solar Car uses a telemetry processor to collect, compute, and transmit data to the driver of the car and a nearby chase vehicle. The original processor had deteriorated from environmental extremes and vibration. There were also problems with electromagnetic interference from the high efficiency electric motor switching electronics, difficulties with the many unplanned additions made to the processor in the field, and the unstructured software that was becoming difficult to maintain. This project consists of creating a replacement telemetry system that is more robust mechanically, and electrically, substantially improving the EMI performance of the device, and reworking the hardware and software to make it easier to maintain and upgrade.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Modern telemetry systems using state of the art field programmable gate arrays (FPGAs) and signal processing components require lower voltage supplies to support various CMOS core geometries while still needing multiple higher voltage rails to support legacy interfaces. Addressing these power supply requirements efficiently requires switching power supply topologies that if left unchecked can generate high input surge currents and high levels of detrimental noise for both the sensitive analog signal processing circuitry and the power supply input source. This paper focuses on the design considerations and tradeoffs associated with implementing an efficient telemetry encoder power supply while mitigating the resulting noise effects typically associated with switching power supplies. This noise can negatively affect the power supply input source and the linear signal processing circuitry within the telemetry encoder.

This exploratory study into content teacher views on English as the medium of instruction (EMI) in federal tertiary settings in the United Arab Emirates (UAE) was conducted to add to the emerging number of EMI studies in the country and the Arabian Gulf. While other UAE studies have canvassed views from two or more stakeholders, this study looked to focus only on teachers. Working within an interpretive paradigm, rich data were sought from a purposive sample of 45 teachers for an open questionnaire and 9 teachers for semi-structured interviews; the interview themes emanating from questionnaire data analysis. The research framework was built on the researcher’s own experiences in the research context, the assumptions that emerged from those experiences and a review of pertinent themes from the literature, which tended to be grounded in critical theory. These concepts were the macro-policy areas of education and language policy, the synthesised analysis of language policy in education and subsequently a review of themes emerging from EMI studies globally, regionally and in the UAE, which led to a focus on the problem areas of language proficiency and appropriate language pedagogy for this specific research context. Findings suggest that although there is some support for EMI among the sample there is also recognition of attendant problems with the policy caused in the main by students’ insufficient language ability for Bachelor’s study in English and question marks over the need to aspire to native speaker proficiency in a society where various Englishes as a lingua franca are used between citizens who do not use English as their mother tongue. These causes lead students and teachers to enact policy to create learning opportunities. Enactments include skills avoidance, simplifying materials, reducing content and code-switching into Arabic. The absence of Arabic in the higher education curriculum is also questioned, given evidence that it is relevant for students’ future employment; be it in the public or private sector. Recommendations include that English remain an integral part of the curriculum given its relevance for later employment but that the choice of EMI as the model for learning be reviewed to see if other approaches may be more appropriate. It is also recommended that Arabic be included in the curriculum in some form given its importance for students’ careers. Finally, if EMI remains the chosen linguistic approach, teachers are recommended to continue enacting as part of their professional practice to ensure that their students get some benefit from their relatively challenging study environment.