title: Efficiency enhancements to a linear AC voltage regulator: Multi-transformer  and multi-winding designs

authors: Wijesooriya, Priyanwada Nimesha

subjects: Linear AC voltage regulator

abstract: Utility companies are expected to distribute electricity that conforms with international or national standards related to RMS voltage fluctuations. However, RMS voltage variations sometimes exceed acceptable limits and this demands consumer-end voltage regulators. Commercial AC regulators such as (i) servo-driven variacs, (ii) ferro-resonant, (iii) transformer tap changers, (iv) solid-state types, have their own advantages and limitations. Common issues include (a) slow response time, (b) low efficiency and flattened-output waveform, (c) tap dancing and related switching issues, (d) harmonics and RFI/EMI at the output, respectively.

The linear RMS AC voltage regulator is a patented technique developed in the late 1980s to address most of the above issues. It is a solid-state, single-phase system that employs a line-frequency transformer with its primary connected in series with an AC-operable variable impedance based on power transistors. The secondary winding is placed in series with the varying AC input, so that the induced secondary voltage acts as a correction signal to maintain the output at the desired value. A feedback circuit varies the effective impedance of the transistor-array, thus, manipulate the induced secondary voltage to regulate the output.

This is a linear technique that allows seamless transition between boost to buck mode. However, this comes at the cost of lower efficiency at high AC input, particularly when line voltage goes beyond the nominal value.  

Commercial partner, Thor Technologies, Australia, wanted the team to modify their servo-driven AC regulator (PS-10), based on our technique with efficiency in the range of 90-95% and the response time improved by about 10 times.

During development of a commercial prototype, the author implemented two potential solutions: (i) multi-transformer and (ii) multi-winding transformer based techniques to overcome the reduced efficiency during buck-mode operation, an issue inherent to the basic linear AC technique. 

Thesis was aimed at improving the power stage of the linear technique while maintaining the already developed analog control loop with true RMS regulation capability. thesis presents two alternative transformer solutions to reach efficiencies in the range of $90-95\%$ on a laboratory prototype of 500VA. Experimental results were validated by constructing a theoretical model for the two transformer configurations, supported by an equivalent circuit analysis using MATLAB and LTSpice software.

text: Efficiency enhancements to a linear AC voltage regulator: Multi-transformer  and multi-winding designs Utility companies are expected to distribute electricity that conforms with international or national standards related to RMS voltage fluctuations. However, RMS voltage variations sometimes exceed acceptable limits and this demands consumer-end voltage regulators. Commercial AC regulators such as (i) servo-driven variacs, (ii) ferro-resonant, (iii) transformer tap changers, (iv) solid-state types, have their own advantages and limitations. Common issues include (a) slow response time, (b) low efficiency and flattened-output waveform, (c) tap dancing and related switching issues, (d) harmonics and RFI/EMI at the output, respectively.

The linear RMS AC voltage regulator is a patented technique developed in the late 1980s to address most of the above issues. It is a solid-state, single-phase system that employs a line-frequency transformer with its primary connected in series with an AC-operable variable impedance based on power transistors. The secondary winding is placed in series with the varying AC input, so that the induced secondary voltage acts as a correction signal to maintain the output at the desired value. A feedback circuit varies the effective impedance of the transistor-array, thus, manipulate the induced secondary voltage to regulate the output.

This is a linear technique that allows seamless transition between boost to buck mode. However, this comes at the cost of lower efficiency at high AC input, particularly when line voltage goes beyond the nominal value.  

Commercial partner, Thor Technologies, Australia, wanted the team to modify their servo-driven AC regulator (PS-10), based on our technique with efficiency in the range of 90-95% and the response time improved by about 10 times.

During development of a commercial prototype, the author implemented two potential solutions: (i) multi-transformer and (ii) multi-winding transformer based techniques to overcome the reduced efficiency during buck-mode operation, an issue inherent to the basic linear AC technique. 

Thesis was aimed at improving the power stage of the linear technique while maintaining the already developed analog control loop with true RMS regulation capability. thesis presents two alternative transformer solutions to reach efficiencies in the range of $90-95\%$ on a laboratory prototype of 500VA. Experimental results were validated by constructing a theoretical model for the two transformer configurations, supported by an equivalent circuit analysis using MATLAB and LTSpice software.

year: 2020

title: 2024 Moana Oceania soil judging competition handbook

authors: Smith, Carol

subjects: Allophanic Soils

abstract: Welcome to the 2024 Moana Oceania Soil Judging Competition, jointly hosted by the New Zealand Society of Soil Science (NZSSS) and Soil Science Australia (SSA) and held this year in the stunning volcanic landscape of Rotorua, New Zealand.

This prestigious competition has become a much-anticipated event on both of our Societies’ calendars. This year's event provides an unparalleled opportunity to learn alongside participants from various soil-related backgrounds, including university students, regional council scientists, land managers, consultants, and general soil enthusiasts. Participants have travelled from every Australian state, across New Zealand and from a number of Pacific Island nations.

Soil judging is one of the best possible training grounds for aspiring soil professionals and those working professionals who wish to add a string to their bow of skills. Whether you have an interest in research, teaching, or consultancy, within academia, government or the private sector, there is no shortage of career possibilities in soils.

Students are our next generation of soil scientists and land managers and for that reason you play a critical role in both the NZSSS and SSA. Both nationally, and through our branches, our societies support students through a range of initiatives:
• Travel grants to attend the biennial national soil science conference.
• Financial support to attend the national soil judging competition and for the absolute best competitors, to attend the World Congress of Soil Science.
• Awards, presented at national conferences and by our branches.
• Reduced membership fees for our societies and registration fees for events.
• Great opportunities for mentoring and networking.

Over 3 days, we aim to equip participants with the soil description and classification skills that are vital for interpreting the best management and land use for any given soils. The practice and competition days will be intense, as your problem-solving skills, academic credentials and practical experience will be put to the test. This is your opportunity to show how much you have learned about soil description and classification and how you apply that knowledge in the field, often under pressure. Make the most of the training sessions, in the lead up to the competition day, and the chance to learn from some of our finest soil scientists as well as your fellow entrants.

Remember, beyond the technical challenges, you will also discover the value of ongoing education and professional development and the satisfaction that comes from strong teamwork. Most importantly, we hope this experience reinforces your commitment to sustainable land management and to protecting one of our nation’s most precious natural assets - our soil.

text: 2024 Moana Oceania soil judging competition handbook Welcome to the 2024 Moana Oceania Soil Judging Competition, jointly hosted by the New Zealand Society of Soil Science (NZSSS) and Soil Science Australia (SSA) and held this year in the stunning volcanic landscape of Rotorua, New Zealand.

This prestigious competition has become a much-anticipated event on both of our Societies’ calendars. This year's event provides an unparalleled opportunity to learn alongside participants from various soil-related backgrounds, including university students, regional council scientists, land managers, consultants, and general soil enthusiasts. Participants have travelled from every Australian state, across New Zealand and from a number of Pacific Island nations.

Soil judging is one of the best possible training grounds for aspiring soil professionals and those working professionals who wish to add a string to their bow of skills. Whether you have an interest in research, teaching, or consultancy, within academia, government or the private sector, there is no shortage of career possibilities in soils.

Students are our next generation of soil scientists and land managers and for that reason you play a critical role in both the NZSSS and SSA. Both nationally, and through our branches, our societies support students through a range of initiatives:
• Travel grants to attend the biennial national soil science conference.
• Financial support to attend the national soil judging competition and for the absolute best competitors, to attend the World Congress of Soil Science.
• Awards, presented at national conferences and by our branches.
• Reduced membership fees for our societies and registration fees for events.
• Great opportunities for mentoring and networking.

Over 3 days, we aim to equip participants with the soil description and classification skills that are vital for interpreting the best management and land use for any given soils. The practice and competition days will be intense, as your problem-solving skills, academic credentials and practical experience will be put to the test. This is your opportunity to show how much you have learned about soil description and classification and how you apply that knowledge in the field, often under pressure. Make the most of the training sessions, in the lead up to the competition day, and the chance to learn from some of our finest soil scientists as well as your fellow entrants.

Remember, beyond the technical challenges, you will also discover the value of ongoing education and professional development and the satisfaction that comes from strong teamwork. Most importantly, we hope this experience reinforces your commitment to sustainable land management and to protecting one of our nation’s most precious natural assets - our soil.

year: 2024

title: The arguing genre and the explaining genre: A comparison in terms of discourse relational analyses of texts written in English and texts written in Māori

authors: Crombie, Winifred

subjects: Māori linguistics

abstract: There is a commonly held belief that those who are immersed in indigenous cultures have a tendency, when constructing academic texts, to avoid sequential, deductive argumentation. We report here on a comparison of two groups of texts exhibiting two different genres - 'explaining' and 'arguing'. One group of texts was written in Māori by indigenous authors, the other group was written in English by non-indigenous authors. Our findings are that although the percentage use of logico-deductive relationships is roughly equivalent for both groups of texts/ writers in the case of the explaining genre, the Māori texts/ writers use almost twice the percentage of logico-deductive relationships as do the English texts/ writers.

text: The arguing genre and the explaining genre: A comparison in terms of discourse relational analyses of texts written in English and texts written in Māori There is a commonly held belief that those who are immersed in indigenous cultures have a tendency, when constructing academic texts, to avoid sequential, deductive argumentation. We report here on a comparison of two groups of texts exhibiting two different genres - 'explaining' and 'arguing'. One group of texts was written in Māori by indigenous authors, the other group was written in English by non-indigenous authors. Our findings are that although the percentage use of logico-deductive relationships is roughly equivalent for both groups of texts/ writers in the case of the explaining genre, the Māori texts/ writers use almost twice the percentage of logico-deductive relationships as do the English texts/ writers.

year: 2005-02