Convertisseurs génériques Applications pour le domaine aéronautique

THESE
présentée pour obtenir le titre de
DOCTEUR DE L’INSTITUT NATIONAL POLYTECHNIQUE DE TOULOUSE
Ecole doctorale : Génie Electrique, Electronique, Télécommunications
Spécialité : Génie Electrique
Par
Jérôme MAVIER

Convertisseurs génériques à tolérance de panne
Applications pour le domaine aéronautique
Abstract
Electric power is of increasing importance in aeronautical systems. As a consequence,
static converters have become widespread, and power electronics is crucial for improving
performance, reliability and competitiveness.
The aim of this thesis is to contribute to the design of electrical networks by using
modular generic converters. To determine their structure, an inventory of power electronics
applications is carried out in the framework of a "more electric" aircraft.
The modularity of these power conversion blocks opens the way for power
segmentation and redundancy, that enables systems availability to increase. Following this
approach, several fault-tolerant inverter topologies are compared, both analytically and by
simulation based on the physical model of a flight surface electrohydrostatic actuator.
For the experimental studies, power electronics modules are designed to operate a
reconfigurable inverter that is dedicated to a permanent magnet synchronous motor drive.
Connected to the neutral point of the wye-connected motor, this inverter has a fourth leg that
acts as a mutualised redundancy.
Lastly, to extend the power electronics generic module’s field of application, three
AC/DC converter topologies are proposed in order to improve power management, in
comparison with conventional topologies, with respect to electrical and thermal design
criteria.

Soutenue le 22 mars 2007 devant le jury composé de :
MM. P. LE MOIGNE Rapporteur
F. MEIBODY-TABAR Rapporteur
F. FOREST Examinateur
L. PRISSE Examinateur
F. RICHARDEAU Encadrant
H. PIQUET Encadrant
P. ROLLIN Invité
Thèse préparée au Laboratoire Plasma et Conversion d’Energie (LAPLACE) – site ENSEEIHT
Unité Mixte de Recherche INPT – UPS – CNRS N°5213

DESIGN METHODOLOGY OF A HIGH POWER DENSITY

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Design of a 320W Telecoms DC/DC converter.

Introduction
This report describes the design of a 320W Telecoms DC/DC converter. A push-pull forward
converter running with current mode control using the LM5030 from National Semiconductor
delivers high performance and small solution size. Custom planar magnetics from Payton
have been used throughout to reduce component build height, increase efficiency and aid
cooling.
This report contains target specification, schematic, bill of materials, magnetics design
information as well as a detailed design analysis. A full set of performance measurements is
also included taken from the prototype unit shown in Figure 1. Measurements include
conversion efficiency, power stage device temperature rise, line/load regulation, start-up
behaviour, transient load response and loop gain/phase characteristic.

IR Thermography

The design of reliable power electronic converter systems depends
partly on an accurate knowledge of the power stage component
operating temperatures under extremes of load and input voltage.
This article demonstrates how the use of modern infra-red (IR)
imaging techniques can significantly enhance the design qualification
process and show up potential problems at a very early stage in
the product development cycle. The techniques highlighted are
applicable to any power converter system or electronic product
where knowledge of component operating temperatures is
important for reliability modelling and lifetime prediction.
By Dr. Iain Mosely, Technical Director, Converter Technology Ltd

One of the main limiting factors affecting the power capability and
reliability of any electronic power converter system is the operating
temperature of key power stage components. Excessive component
temperature will reduce product operating lifetimes and could result
in early field returns. Traditionally, thermocouples are used to
measure the operating temperature of components.
Whilst thermocouples can give very accurate temperature
measurements, they do have a few potential drawbacks:
• Thermocouples can pick up noise if they are placed near to power
components with high dv/dt switching waveforms present and this
can give misleading measurement results.
• Thermocouples will sink a small amount of heat away from the device
they are attached to. For physically small components, this can lead
to measurement inaccuracy.
• Thermocouples are often only placed on components which are
expected to show a reasonable temperature rise. Other components
may not be monitored at all and this could lead to problems if a
design error leads to a high operating temperature on a component
which hasn’t been monitored.

IR thermography is a non-contact measurement technique which
uses a calibrated infrared camera to form athermal image of the
system under test.
As the measurement technique is noncontact, the noise susceptibility
and heatsinking effects sometimes encounteredwith thermocouples
are no longer an issue. More importantly, an entire PCB can be imaged
which immediately shows up any hotspots or problem components that
may have otherwise been overlooked.

An example thermographic image ofa power converter is shown
in Figure 1.The power converter used has an issue with a snubber
TVS diode which can be seen to be running at >150°. Using the
thermal imaging camera is this example would immediately alert
the designer to a potential problem with the PSU before it reaches
the pre-production or production stage. The real value of thermography
in power electronic design is this ability to rapidly flag potential
design issues at a very early stage.