An investigation into sinusoidal current output switchmode converters

**Authors:**Britz, Pierre**Date:**2011-11-10**Subjects:**Switching circuits , Switching power supplies , Electric circuits , Electric current converters**Type:**Thesis**Identifier:**http://ujcontent.uj.ac.za8080/10210/378134 , uj:7267 , http://hdl.handle.net/10210/3942**Description:**M.Ing. , The focus of the project is on the design of a variable output current source applied in the testing of circuit breakers. The possibility of the use of high-frequency, switch mode converters for the application, will be investigated. The expectation is the improvement of the system currently in use, with the help of a power electronic converter. For the application, a 1 to 200A adjustable current source must be developed, which will be powered from the 220V, 50Hz network. A number of possible solutions to the problem will be investigated. One of the challenges of the project is that the output of the converter must be a current and not a voltage, which is normally the case. Based on mathematical calculations and practical results, the best possible solution to the problem is obtained. An optimum system is presented, which meets the desired specifications.**Full Text:**

**Authors:**Britz, Pierre**Date:**2011-11-10**Subjects:**Switching circuits , Switching power supplies , Electric circuits , Electric current converters**Type:**Thesis**Identifier:**http://ujcontent.uj.ac.za8080/10210/378134 , uj:7267 , http://hdl.handle.net/10210/3942**Description:**M.Ing. , The focus of the project is on the design of a variable output current source applied in the testing of circuit breakers. The possibility of the use of high-frequency, switch mode converters for the application, will be investigated. The expectation is the improvement of the system currently in use, with the help of a power electronic converter. For the application, a 1 to 200A adjustable current source must be developed, which will be powered from the 220V, 50Hz network. A number of possible solutions to the problem will be investigated. One of the challenges of the project is that the output of the converter must be a current and not a voltage, which is normally the case. Based on mathematical calculations and practical results, the best possible solution to the problem is obtained. An optimum system is presented, which meets the desired specifications.**Full Text:**

Procedure for determining the stray capacitance of a switching circuit node

**Authors:**Naude, Tonya**Date:**2009-02-26T12:21:12Z**Subjects:**Electric capacity , Capacitance meters , Electromagnetic interference , Switching circuits , DC-to-DC converters**Type:**Thesis**Identifier:**uj:8169 , http://hdl.handle.net/10210/2174**Description:**M.Ing. , This study focuses its attention on conducted common mode EMI. Common mode current is the current that flows from an electrical circuit to a zero reference plane and back to the circuit again. It is known that the manner in which the common mode current flows is through stray capacitances that form between the electrical circuit and the zero reference. This study was aimed at developing a method to measure the value of the stray capacitance of a switching circuit. Determining the value of the stray capacitance by taking physical measurements on a circuit board is a challenge for a number of reasons, one of which is that great care should be taken not to add to the stray capacitance by means of the measuring equipment. By measuring the value of the stray capacitance, it will be possible to model the occurrence of Common Mode EMI better and more accurately. This could, in turn, lead to a reduction in EMI. Any body of an arbitrary shape, size and material exhibits a self-capacitance with respect to a zero reference frame. This principle, together with the principle of conservation of charge, also applies to electrical components, or circuits as a whole. The experimental work was performed on a buck DC-DC converter. The circuit was simplified to aid in analysis. By varying the value of an external capacitance and taking basic measurements, it is then possible to uniquely determine the absolute values of the self-capacitances. For every pair of external capacitance values placed in the circuit (of which one can be =0pF), a value for stray capacitance is calculated. Many data points were recorded with many different external capacitors in the circuit, resulting in a variety of stray capacitance values. In order to obtain a single value, a weighted mean of all the values was calculated. The values obtained in this proposed method of measuring the stray capacitance compares well with that obtained using the Finite Element Method. The advantage of the method presented here is that the self-capacitances are determined under the actual operational conditions, no specialised equipment is required and no unique handling of parasitics is needed. The method relies on very simple measurements and no complex data manipulations are required.**Full Text:**

**Authors:**Naude, Tonya**Date:**2009-02-26T12:21:12Z**Subjects:**Electric capacity , Capacitance meters , Electromagnetic interference , Switching circuits , DC-to-DC converters**Type:**Thesis**Identifier:**uj:8169 , http://hdl.handle.net/10210/2174**Description:**M.Ing. , This study focuses its attention on conducted common mode EMI. Common mode current is the current that flows from an electrical circuit to a zero reference plane and back to the circuit again. It is known that the manner in which the common mode current flows is through stray capacitances that form between the electrical circuit and the zero reference. This study was aimed at developing a method to measure the value of the stray capacitance of a switching circuit. Determining the value of the stray capacitance by taking physical measurements on a circuit board is a challenge for a number of reasons, one of which is that great care should be taken not to add to the stray capacitance by means of the measuring equipment. By measuring the value of the stray capacitance, it will be possible to model the occurrence of Common Mode EMI better and more accurately. This could, in turn, lead to a reduction in EMI. Any body of an arbitrary shape, size and material exhibits a self-capacitance with respect to a zero reference frame. This principle, together with the principle of conservation of charge, also applies to electrical components, or circuits as a whole. The experimental work was performed on a buck DC-DC converter. The circuit was simplified to aid in analysis. By varying the value of an external capacitance and taking basic measurements, it is then possible to uniquely determine the absolute values of the self-capacitances. For every pair of external capacitance values placed in the circuit (of which one can be =0pF), a value for stray capacitance is calculated. Many data points were recorded with many different external capacitors in the circuit, resulting in a variety of stray capacitance values. In order to obtain a single value, a weighted mean of all the values was calculated. The values obtained in this proposed method of measuring the stray capacitance compares well with that obtained using the Finite Element Method. The advantage of the method presented here is that the self-capacitances are determined under the actual operational conditions, no specialised equipment is required and no unique handling of parasitics is needed. The method relies on very simple measurements and no complex data manipulations are required.**Full Text:**

A modular switchmode power supply for an interlocking system

**Authors:**Hefer, Andre**Date:**2012-09-10**Subjects:**Switching circuits , DC-to-DC converters**Type:**Mini-Dissertation**Identifier:**uj:9888 , http://hdl.handle.net/10210/7287**Description:**M.Ing. , A signal is an apparatus that safely provides visual information to the train driver of availability, route and safety of the way ahead and enables him to decide how to control his train. These signal units consist of a number of lights that display the required aspect to the train. The need for safer and more effective train control methods become more important as the number, speed, mass and length of trains increase. By extending the number of aspects to include 'flashing-aspects, i.e. switching some of the aspects on and off at a constant rate, more information can be conveyed to the train driver. A systems) needs to be introduced into the interlocking in order to produce these aspects. This dissertation explores the implementation of a dc-to-dc switching converter, in a relay interlocking environment, in order to produce an oscillating voltage for these flashing aspects. The reliability of the system is improved by a modular design of power supplies and equal current sharing is implemented by means of current-mode control. The results presented show the system performing satisfactory in the signalling environment and being able to cope with varying loads.**Full Text:**

**Authors:**Hefer, Andre**Date:**2012-09-10**Subjects:**Switching circuits , DC-to-DC converters**Type:**Mini-Dissertation**Identifier:**uj:9888 , http://hdl.handle.net/10210/7287**Description:**M.Ing. , A signal is an apparatus that safely provides visual information to the train driver of availability, route and safety of the way ahead and enables him to decide how to control his train. These signal units consist of a number of lights that display the required aspect to the train. The need for safer and more effective train control methods become more important as the number, speed, mass and length of trains increase. By extending the number of aspects to include 'flashing-aspects, i.e. switching some of the aspects on and off at a constant rate, more information can be conveyed to the train driver. A systems) needs to be introduced into the interlocking in order to produce these aspects. This dissertation explores the implementation of a dc-to-dc switching converter, in a relay interlocking environment, in order to produce an oscillating voltage for these flashing aspects. The reliability of the system is improved by a modular design of power supplies and equal current sharing is implemented by means of current-mode control. The results presented show the system performing satisfactory in the signalling environment and being able to cope with varying loads.**Full Text:**

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