The automobile starter-generator based on the switched reluctance machine

THE AUTOMOBILE STARTER-GENERATOR BASED ON THE SWITCHED RELUCTANCE MACHINE

Semen А. Salov, Eugene A. Soldatov

The Scientific head Professor Sergey I. Malafeev

Department of Information Technologies

Vladimir State University

Gorky st. 87, Vladimir, 600000, RUSSIA

Tel: +7(4922) 279992, E-mail: salovsemen@mail.ru

Abstract – the opportunity of application switched reluctance machine of various configurations as the starter – generator device for the automobile is considered. Estimated calculation of unit parameters for switched-reluctance machine several configurations, the analysis of operating modes is lead at various topology of converters, research of operating modes of the starter - generator on the basis of imitating modelling.

1. INTRODUCTION

Transformation of electric energy in mechanical and mechanical energy in electric is widely distributed in the automobile now. The devices developed for it, is apply some decades. The starter based on the DC machine, the generator representing the synchronous or asynchronous machine concern to them. Structurally the starter and the generator are carried out as the independent blocks combined by mechanical transfer to cranked shaft of the internal-combustion engine (I.C.E.).

Now there is an intensive development of new type of the electric machine named switched-reluctance [1]. It can serve as the combined starter-generator device that uses in a starter mode short time, rotating cranked shaft I.C.E. with the set speed, and long time uses in a generator mode. Accommodation switched reluctance machines (SRM) directly coupled to the I.C.E. cranked shaft between the crankgear and the catching device is the most convenient. Short-width execution SRM for this purpose it is necessary.

SRM gives the following advantages the traditional decision: refusal of two mechanical transfers, reduction of a flywheel weight, brushless starter construction, and increase of the fault tolerance and reduction in service up requirements. The disadvantage of the SRM is necessity of use of the voltage converter and the special pulse shaper.

Maintenance of the sufficient starting torque at minimal mass and dimensions parameters, and also reduction of the electric power losses by active elements of the converter is complexity by development of the incorporated starter - generator SRM-basis unit. Various SRM configurations and various topology converters for the decision of the given problems further are investigated.

There are some developments in the field of the incorporated SRM starter – generator now, however they do not contain computations and results of modelling of devices with real parameters.

2. The comparative analysis of SRM configurations

It is necessary to determine parameters from a condition of satisfaction to requirements on rated power at the limited overall dimensions at designing switched reluctance machine. Maintenance of normal functioning at the lowered battery voltage is important for a developed starter. Also it is necessary to take into account losses on active elements of the power converter.

Switched reluctance machine concern to the basic settlement parameters the following: rotor poles numbers, stator poles numbers, number of windings and others.

Is lead rough calculation purpose of definition of an optimum configuration SRM from the point of view of maintenance of the rated torque, rated speed, mass-dimension parameters and cost. As the initial data for starter mode the following parameters have been accepted:

– Rated torque T_r,                                                   30 N×m,

– Rated speed n_r,                                                     180 rpm,

– DC link voltage U,                                                             10 V,

– Stator radius r_st,                                                   0,10 m,

– Stator radius rotor radius relation r_st/r_rot,         0,55,

– Airgap lenght a,                                                   0,003 m.

Two configurations SRM were examined for the projected starter - generator: 6/4 and 12/8, where 6 and 12- stator poles, 4 and 8- rotor poles. Three-phase execution switched reluctance machine was supposed.

The estimated calculation which has been carried out by means of applied program SRDaS, has shown, that for above mentioned conditions the most preferable is 6/4 SRM configuration. This configuration is characterized manufacturing simplicity, the high rated torque, a smaller a winding current, higher flux linkage. However as against a configuration 12/8 take place high torque ripple, but it is not serious disadvantage at the high rotor weight.

For the further research overall dimensions SRM have been calculated. The stator width makes 7,8 cm, resistance of phase r_ph=0,026 Ohm. Copper expenses at this SRM configuration are minimal and make 35 % a total machine cost.

2. Imitating modelling in Matlab/Simulink environment

The choice of the optimum voltage converter topology is the important question at designing the electric drive basis on switched reluctance machine. The basic criterion thus is reduction of number of semi-conductor elements in the circuit at maintenance the set characteristics of the engine.

Two types of converters have been considered: classical converter and the suppression resistor converter.

Fig. 3 illustrates the circuit of the classical converter. The advantages of this converter topology are [2]: the energy from the off-going phase is transferred back to the source, which results in useful utilization of the energy. The main disadvantage of this topology is the higher number of switches required in each phase which makes the converter expensive. Also, for low-voltage (automotive) applications the forward voltage drops in two devices may be significant compared to the available dc bus voltage.

Fig. 3 illustrates the circuit of the suppression resistor converter [2]. The advantages of the suppression resistor converter are: lower number of switching devices, simple commutation required and therefore very low cost, simple control of the switches, faster demagnetization of phases.

Fig. 2. The classical converter                               Fig. 3. The suppression resistor converter