Jean-Paul Vilain

A New PWM Strategy to Reduce the Inverter Input Current Ripples

This paper deals with an innovating pulsewidth modulation (PWM) strategy allowing reduction of the DC input current ripples in classical operating area of adjustable-speed drives, and also maintaining a good quality of AC current waveforms and limited switching losses in the inverter. Thus, such a strategy is an interesting solution within embedded systems. Theoretical principles of the proposed method are introduced. Then, simulation results highlight the benefits of this algorithm compared to classical PWM control. Finally, a DSP-base implementation has been performed, and effectiveness of this strategy is confirmed by experiments for a starter-generator application.

A Direct Digital Technique Implementation of General Discontinuous Pulse Width Modulation Strategy

This paper presents direct digital technique-generalized discontinuous pulse width modulation (PWM) - a new implementation method for an optimal discontinuous PWM (DPWM) in terms of switching losses of the inverter on an embedded system. At each sampling period, an optimal choice is done in order to clamp one of the three half-bridges. Its advantages compared to classic ones (DPWM) are as follows: needless to know the load power factor, operational under steady-state and dynamic operating conditions, and low computation time. The proposed algorithm is then verified by simulation. Experimental results, based on a resistance-inductance load and a starter-generator application, are provided to show its effectiveness.

A new modelling of DC machines taking into account commutation effects

In some specific manufactured electromechanical applications, power electronic converters must be avoided due to hostile environment. In such a context, stand-alone DC machines are good candidates because of their high reliability and low cost. However, the mechanical commutation is a big problem in this kind of machine especially in high current and low voltage applications. Losses due to arching contacts can be significant. The authors present an original technique to take into account every electrical aspect of brushes contacts (mechanical sliding contact and arching contact). The aim of this study is to determine currents and voltages of conductors during commutation in order to reduce significantly losses due to sliding contact. These evolutions are very important data for finite element analysis too.

Innovative permanent-magnet starter motors for automotive micro-hybrid applications

This paper provides a review of several original improvements of 6-ferrite 12-V brushed DC starters, based on unconventional uses of Halbach arrays. Electromagnetic behaviors are firstly analyzed, especially when specific to this saturated high-current automotive application; hence the armature magnetic reaction and its link to commutation. After explaining which properties of Halbach arrays can be exploited, each novel design is detailed. Prototypes have been built and tested, so all three variants of motors are validated, whatever the type of material implemented, sintered or bonded magnets, even combined with an ironless armature instead of the usual slotted and laminated one. The proposals appear more expensive, but occur to be a great help to applications, showing enhancements in dynamic performance and brush durability, as two mandatory key features for modern starting systems.

Behavior analysis of a DC brush machine by space vector theory

The authors show that the space vector modelling, classically used for synchronous or asynchronous machines, can be applied with profit to DC machines. By leaning on the example of a permanent magnets machine and by comparing the results of the modelling with the experimental measurements, we notice that this process applies perfectly and allows taking into account the effects of the saturation or the possible effects of salience on the armature. This modelling constitutes an effective tool to analyze the role of every element of the machine and to lead an optimization approach.

Sensorless control of a wound rotor synchronous belt-driven starter-alternator

The main purpose of this work is to achieve a low-cost sensorless drive for wound rotor synchronous belt-driven starter-alternator (StARS). These electrical machines manufactured by automotive suppliers are intended to equip light cars. Classically, the self-commutation operation of the StARS is controlled by electromechanical position sensors. However, these last suffer from complex wiring and reliability issues. To overcome these problems, authors propose a sensorless control method which deals with initial rotor position detection and motor parameter identification at stand-still. A back-emfs estimation method suitable for non-zero speeds is presented as well as a DSP implementation of the suggested sensorless technique. Experimental results verify the good operation of the proposed solution.