55_

Full Paper Int. J. on Recent Trends in Engineering and Technology, Vol. 8, No. 2, Jan 2013

Design of Switched Reluctance Motor for Three Wheeler Electric Vehicle T.Dinesh kumar1 and M.Anand2 1

Department of EEE, PSG College of Technology, Coimbatore, India Email: dineshkumarped@gmail.com 2 Department of EEE PSG College of Technology, Coimbatore, India Email: and@eee.psgtech.ac.in

Abstract—Switched Reluctance M achines (SRM ) offer attractive attributes for automotive applications. Low cost, high reliability, and competitive weight and efficiency combine to make the switched reluctance (SR) motor drive a strong candidate for application in future electric vehicle (EV) propulsion systems. This paper proposes a methodology to determine separately the peak and continuous power ratings of a switched reluctance motor (SRM) for electric propulsion of an electric vehicle (EV).same machine have to deliver peak and continuous power for different road load condition of vehicle. Then gives switched reluctance design guidelines for battery operated electric vehicles. Finally, it presents the design and simulation of a switched reluctance motor power train.

TABLE I. EV SPECIFICATIONS

Index Terms—switched reluctance motor, electric vehicle, power rating

I. INTRODUCTION The Automotive sector has undergone significant changes in the last few decades. Major emphasis has been placed on increasing efficiency, enhancing performance, reducing emissions, and developing a sustainable environment. ( ta), maximum slope or gradient (α ), rolling coefficient (Co), This has led to an increased interest in the area of electric EV frontal area (A , dragging coefficient (Cd), wheel radius (r), vehicles (EVs) over the last decade In order to improve the gear-box ratio(G). The EV specifications considered in this effectiveness of an EV.There is a great demand for efficient, paper are listed in Table I. quiet, reliable, and cost-effective motor drives for propulsion The vehicle speed is related to the electric motor speed systems in electric vehicles. Owing to a rigid structure and through the gear ratio and the wheel radius. All the results the absence of magnetic source on the rotor, a switched reare reported in terms of the vehicle speed to eliminate the luctance machine (SRM) is inherently robust and cost effecneed of considering the values of the gear ratio and wheel tive. The performance of an electric machine can be described radius (we assumed a single gear ratio as it is typical in EV). by the following key parameters: 1) power density; 2) strucIn the analysis, the total losses are equal to the sum of the tural integrity; and 3) manufacturing cost. The EV Technical copper and total-iron losses. In the following sections, we Specifications [1] and the NEMA Standard for Motors and explain the procedure proposed for determining (sizing) the Generators [2] address the rating (sizing) of electric motors SRM ratings for EV propulsion. used in an electric vehicle. Hence, they are used very appropriate throughout this paper. These standards require that II. PROCEDURE FOR SIZING THE SRM the peak and continuous power ratings be identified sepaIn a complete specification of the EV electric motor: 1) the rately for a complete specification of an electric motor inpeak and continuous power ratings are identified separately tended for electric propulsion of an EV. This paper presents a and 2) the peak power is corrected according to the detailed method to determine the two power ratings given requirements imposed by all considered driving schedules the vehicle specifications. A procedure for determining the and operating conditions [3]. The peak power rating is also peak power rating of the drive used for EV propulsion is called the rated or continuous power; this might lead to overdescribed. dimensioning of the electric motor although this approach For a particular electric propulsion application, the EV provides a safety margin. main specifications are vehicle maximum mass (M), maximum We can determine separately the peak power and and rated speeds (Vev,max and Vev,r), acceleration times 31 © 2013 ACEEE DOI: 01.IJRTET.8.2.55

Full Paper Int. J. on Recent Trends in Engineering and Technology, Vol. 8, No. 2, Jan 2013 continuous power ratings by considering the EV specifications, the SRM operation principles. Initially, the peak power rating Pm,peak of the SRM (electric motor) is calculated from the specified acceleration duty. We then compare this value with: 1) , Pm,max the power for cruising at the vehicle maximum velocity as well as , the powers required when the EV is moving at: 2)Pm,g, 30km/hr on a 3% gradient and ascending a 25% gradient at low speed. The value of Pm,peak is changed to Pm,max or the highest Pm,g if any of these values is greater than the initial value of of Pm,peak .

Continuous power rating Pm,cont of the electric motor (SRM), is determine by driving the vehicle at maximum speed.

In other words, the SRM is capable of delivering this Pm,cont at the chosen speed. The SRM temperature rise under this continuous power rating should be within the limits specified in [4] for each class of insulation. Conventional auto rickshaws are suited to the Indian environment. They are small and narrow, allowing maneuverability on congested roads. They have a top speed of 55 km/h or 34 mi/h and generally carry one to four passengers and their cargo. Despite the apparent advantages in the vehicle design, auto rickshaws present a huge pollution problem in major Indian cities. This is due to poor vehicle maintenance and the use of an inefficient engine with very little pollution control. For better performance and efficiency we can go with electric power for auto rickshaw. In this paper we are taken auto rickshaw for selecting power rating, designing and development switched reluctance motor for battery operated electric vehicle.

TABLE II. PEAK POWER AND CONTINUOUS POWER R ATING

IV. DESIGN OF SWITCHED RELUCTANCE MOTOR Power developed in SRM is given by, Pd = Ke * Kd * K1 * K2 * B * As * D2 * L * Nr (3) Here the stack length is assumed to be as the multiple or submultiples of rotor bore diameter that is L=K*D (4) For non-servo applications the range of K can be 0.25<K<0.7 For servo applications it’s usually the range given by 1<k<3 The specific electric loading is given by As=stator current * No. of conductors (5) ΠD As=2Tph * I * m ΠD m is the number of phases excited at a time in this design taken as m=1 and I is the rms Current through the phase. The specific electric loading in ampere conductors per meter is usually in the range of: 25,000 < As<90000.

In this section switched reluctance motors is designed

by RMxprt. RMxprt uses a combination of analytical and magnetic circuit equations to predict the performance of this motor problem. RMxprt assumes the switched reluctance motor operates with shaft position feedback to synchronize the commutation of the phase currents with precise rotor position single pulse operation is used phase excitation. In the single pulse operation, each phase is energized at the turn-on angle and switched off at the turn-off angle. The difference between the turn-off and the turn-on angle is called the dwell angle. RMxprt supports only switched reluctance motors in which the number of stator poles is greater than the number of rotor poles.

III. VEHICLE KINEMATICS Force propelling the vehicle forward, traction force [4] has to  Overcome rolling resistance  overcome Aerodynamic drag  Force needed to overcome when vehicle climbing slope  Accelerate vehicle Power required for propulsion depends upon acceleration, a=dv/dt m/s2.

(1) Force required to propel vehicle is, Ftr=Frr+Fad+Fg+Fa N (2) A. Srm Peak (Output) Power Rating According to Indian road standard, acceleration for auto rickshaw is a=0.65 m/s2, that is (0-30) km in 12.8 sec  Accelerating from 0 to 30 kmph in 12.8 sec = 5.8 HP  Maintaining 30 kmph in a 6% gradient = 5 HP.  Cruising at the maximum vehicle velocity = 4.5 HP Thus, the peak output power rating Pm, peak of the SRM is specified as 5.8 HP, see Table 2.

V. MACHINE SPECIFICATION The design specifications for the SRM comprise of the required power output P in HP, speed N in rpm, allowable peak phase current Ip in Ampere, and available supply voltage V in volts for the system. Knowing the speed and power output will automatically fix the torque to be developed by the machine [5].Figure 1. Shows the geometry used 4 phase SRM with 6 rotor poles and 8 stator poles. Motor dimensions and design parameters are shown in table III. Figure 2.shows flus linkage at various position with respect to current we can see that flux at unaligned position is 0.04 wb and at aligned position 0.08 wb.

B.Continuous (Output) Power Rating The power requirements at the maximum vehicle velocity of 55km/hr and for sustained speeds on gradients. The continuous power rating Pm,cont of the SRM is specified as 4.5 HP at the SRM rated speed Table II . © 2013 ACEEE DOI: 01.IJRTET.8.2.55

32

Full Paper Int. J. on Recent Trends in Engineering and Technology, Vol. 8, No. 2, Jan 2013

Figure 3. Efficiency vs speed Figure 1. 8/6 Switched reluctance motor TABLE III. MOTOR MAIN PARAMETERS

Figure 4. Output vs speed curve

A. Simulation Results

Figure 5. Torque vs speed

Figure 5.shows torque-speed characteristics of switched reluctance motor. Starting torque should be high to propel the vehicle. Chopper current control is applied to limit starting current and also torque to requirement. Initial torque is locked rotor torque which is limited because it causes sudden jurg in vehicle. Torque produced is 50 Nm during acceleration period, it varies for different road-load characteristics. For maximum speed drive schedule torque is produced 7 Nm required to propel vehicle.

Figure 6.shows inductance at aligned and unaligned positions of stator-rotor pole.inductance profile starts every 45 degree in 8/6 configuration.since βr>βs,θ3-θ4>0 to eliminate negative torque production by making current to zero during this period.

Figure 2. Flux linkage at various position

Figure 3.shows efficiency at various speeds, during acceleration efficiency is good maintained above 75% .for different drive schedule efficiency is maintained minimum above 68%.

Figure 4.shows output power of motor power needed during acceleration in 5.8 HP but SRM machine is delivering 7 HP during acceleration which is enough to climb slope of 10% grading. © 2013 ACEEE DOI: 01.IJRTET.8.2.55

33

Full Paper Int. J. on Recent Trends in Engineering and Technology, Vol. 8, No. 2, Jan 2013 Full Load Operation Data

Figure 6. Inductance profile

B.Design Data Sheet As design and simulation process is completed data sheet of design is generated.this data sheet provides about motor operation lile full load and no-load operation.total material consumption and copper consumption of winding will also be generated.

General Gata motor design parameters are generated in general data sheet.

CONCLUSION Presented an approach for determining the SRM power ratings for a complete specification in an Electric propulsion application. Efficiency still has to be increased that is done by further analysis. Future work is the need to develop a procedure to design a SRM so that the losses are limited to the desired proportion of the total and the thermal duty is kept low. Further analysis with different material and by changing pole angle. Now a day’s permanent magnet motor are replaced by major electric vehicle manufacturers as SRM a perfect candidate for propulsion application.

REFERENCES [1] Thomas Gyllendahl, David Tran, Development of an Auto Rickshaw vehicle suspension, 2012.

[2] NEMA Motor-Generator standards, IEEE Industry Applications, I999.

[3] Solar-Assisted Electric Auto Rickshaw Three-Wheeler, Priscilla Munhall, Student Member, IEEE, M. Lukic Member IEEE, Sanjaka G. Wirasingha Student Member, IEEE, YoungJooLee, Member, IEEE, and Ali Emadi, Senior Member, IEEE, Vol. 59, No. 5, June 2010.

[4] Iqbal Husain, Electrical and Hybrid Vehicles – Design Fundamentals,”CRC Press, 2003.

[5] Praveen Vijayraghavan, Design of Switched Reluctance Motors and Development of a Universal Controller for Switched Reluctance motor and Permanent Magnet Brushless DC Motor Drives, November, 2001.

No- load Operation Data

© 2013 ACEEE DOI: 01.IJRTET.8.2.55

34