Fundamental study of current-fed push-pull resonant converter 

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System structure 1.3.2 and operating principle

An IPT system with a wirelessly coupled primary and secondary allows the secondary to safely move linearly or rotationally to supply the load. Figure 1-4 shows a general configuration of an IPT system [16-18]. As shown, such a structure comprises of two electrically isolated sections: a stationary primary side and a movable secondary side.
The stationary part consists of a primary converter and a primary coil; the main power for the power converter is by rectifying the electric utility at 50Hz or 60Hz, single-phase or threephase. To improve the power transfer in IPT systems, a high frequency converter at the primary side will be used. Due to the existence of air gap transferring power at low frequencies such 50Hz or 60Hz with a reasonable system size is almost impossible in practice [1]. A power converter is mainly adopted to generate a high frequency sinusoidal in range of kHz to MHz frequency level. By increasing the frequency to higher levels, the rapid variation of magnetic field becomes viable and subsequently much stronger induction connection between coils will occur.
The pickup coil of the secondary side is magnetically coupled to the primary side. Because of the loosely coupled properties of IPT system, the induced voltage at the secondary part is lower compared to primary. Thus a power conditioner stage including of rectification and regulation is needed to adjust the power to the load requirements.

General features

An IPT system comprises of two galvanized isolated but magnetically coupled parts. Due to having separated primary and secondary in such systems, several advantages (a, b) and disadvantages (c, d) have been observed which are listed below:
a) Contactless and mobility property: Unlike an electrical transformer, due to the loosely coupled connection between primary and secondary load can move along the track or in the proximity to a coil on the primary side in spite of some lateral movement from the centre of the track. Although the mechanical flexibility between primary and secondary means less power transferring to the load, but this feature of IPT makes it very attractive for both movable and stationary applications.
b) Safe operation, reliability and environmentally friendly: Any electrical or mechanical wear and tear between primary and secondary caused by direct electrical contacts can be eradicated by getting rid of traditional sliding contact in IPT systems. The conventional system could result in possible electrical shock under wet or harsh environments. Because of using two independently enclosed parts in IPT systems this system can operate under harsh environments or in the presence of dust, dirt, water or chemicals. Moreover it does not generate carbon residues; IPT systems can be used in wide range of applications since magnetic field can pass through non-metallic materials. In terms of any effect of IPT systems on human being because the operation system is within 10 KHz to 1 MHz it will not affect communication channels. Based on the research undertaken in [19, 20] IPT has been proved to be harmless on human body. An explanation to this could be because VLFs (Very Low Frequency) are far above any naturally occurring frequencies in the human body but not high enough as radio frequencies to “heat” any human cells. Safe operation of electrical devices will be guaranteed with this feature of IPT systems [1].

Chapter 1: Introduction
1.1 Background
1.2 Slipring applications
1.3 Overview of IPT systems
1.4 Fundamentals of IPT primary power supplies
1.5 Objectives and scope of the Thesis
1.6 Outline of the Thesis
Chapter 2: Fundamental study of current-fed push-pull resonant converter 
2.1 General features of a single phase push-pull converter
2.2 Control strategies of a single phase push-pull converter .
2.3 Electromagnetic structure and power transfer .
2.4 Different resonant frequencies under ZVS operation
2.5 Start-up phase for current-fed push-pull inverters
2.6 Summary
Chapter 3: Proposed multiple phase primary power converter 
3.1 Basic configuration
3.2 Three phase structure control strategies
3.3 Multiple phase structure control strategy
3.4 Summary
Chapter 4: Implementation of the three phase system with CompactRIO
4.1 Introduction to CompactRIO controller
4.2 Controller design .
4.3 Summary
Chapter 5: Experimental results 
Chapter 6: Conclusions and Suggestions for Future Work 

Multiple Phase Primary Side Power Converter for Contactless Slipring Applications

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