International Research Journal of Power and Energy Engineering Vol. 3(2), pp , November, ISSN: x

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1 International Research Journal of Power and Energy Engineering Vol. 3(2), pp , November, ISSN: x IRJPEE Conference Paper Assessment of BLDC Motor for EV Application Considering Vehicle Design Strategy *Chethan S 1 and Abhijith Singh S 2 1,2 School of Electrical & Electronics Engineering, REVA University, Bangalore, India Brush less direct current (BLDC) motors have become a popular choice for electric vehicle (EV) application in recent time because of their outstanding performance and control characteristics. In this paper, a brief review of advantages of electric drive over internal combustion (IC) engine for vehicles is done and a brief comparison is made between BLDC motor and the other motors suitable for EV application. This paper describes the basic design considerations and calculations that need to be followed when selecting the motor ratings for the desired vehicle. Simulation results of Hall Effect sensor signals for controlling the brush less motor and motor characteristics are obtained. Keywords: BLDC motor, EVs, vehicle design, Permanent Magnet Synchronous Moto, AC Induction Motor INTRODUCTION Brush less direct current (BLDC) have become a vital part of the present industry in wide variety of applications starting from medical, computers, electric vehicles, position control, aeromodelling and domestic use. The latest advancement in embedded technology and dedicated controllers available for motor control have eased the control of BLDC motors which was earlier considered as a challenge. The research and development in the magnet material used in rotor design have resulted in obtaining a greater power density with reduced cost ( which have further augment the desire for BLDC motors. LITERATURE REVIEW The present demand for superior performance and exceptional energy efficient motors is due to strict electricity consumption standards and electricity prices. The demand for energy-saving motors is in raise globally on the account of growing demand for motors for cars, household appliances and other motor drive systems. Moreover, to improve the efficiency of the motor, globally the manufacturers are encouraged to follow exacting design and manufacturing standards resulting in energy-saving motors. However, the lack of acknowledgement of the advantages of energy-saving motors, and the high incipient cost, are hampering the development of superior performance motors ( A. Electric drive The electrical actuator is an electromechanical system, which is a combination of electric motor acting as a prime mover and a mechanism for motion or process control. The common application of electric drives includes fans, compressor pumps, excavators, cars and electric locomotive (U.A.Bakshi and M.V.Bakshi, 2009). Typical power drive systems include controllers, motor, transmissions, and driven loads. The key difference between distinct types of electric drive systems is the type of controller. *Corresponding author: Chethan S, School of Electrical and Electronics Engineering, REVA University, Bangalore, India. chethans.eee@gmail.com Co-Author abhijithsinghs@gmail.com

2 Chethan and Abhijith 119 Specific DC motor controller (Herman and Stephen L, 2010) which includes motor starter, switches and operator control or an electronic motor controller called a drive controller that uses the semiconductor having electronic circuitry and software to perform the same function of different DC motor control components ( B. Choice of electric drive over IC engine The main advantage of the motor over the IC engine is that the full torque is provided by the motor at low speed and the fleet rated power can be two or three times the rated power of the motor. These are the features that allow the vehicle to have a peerless acceleration of the nominal rated motor. The motor produces high torque even at zero speed and typically has a constant power characteristic over a wide speed range. Therefore, the motor can be mounted directly on the drive wheel and accelerate from zero speed to the maximum speed (Husain and Iqbal, 1964). Compared with other types of drive systems, electric drives have the following advantages, such as: Control features can be adapted to application requirements, Simple and convenient speed control method. Electric brake can be easily applied, no pollution, Wide range of speed, power, torque rating, more efficient, Brief time overload capacity, Self-starting - No external boot device required, compared with the hydraulic and diesel prime mover, it runs cleaner, with less noise and less maintenance (U.A.Bakshi and M.V.Bakshi, 2009). Introduction to Various Motor Types a. Brushed DC Motor The brush DC motor converts the direct current in the armature coil as shown in Fig 1(a) into an alternating current by the commutator and brush arrangement. When the current flows through the commutator through the armature winding, the electromagnetic field repels the magnet near the same polarity and causes the winding to turn to attract the magnet with opposite polarity. When the armature is rotated, the commutator reverses the current in the armature coil to repel the nearby magnet, thereby causing the motor to rotate continuously. The motor can be driven by DC voltage and current, which is very attractive for low cost applications. The limiting factor is the commutator and brush arrangement causes arcing at the brushes resulting in heat, mechanical losses and electromagnetic interference (EMI) problem %20Fundamentals.pdf). Fig 1 Structures of Different Types of Motors

3 Int. Res. J. Power Energy Engin. 120 b. Brushless DC (BLDC) Motor The BLDC motor uses the internal rotor position feedback for commutation to determine the switching sequence of the phases of stator winding. The layout is unveiled in Fig 1. (b) Feedback normally requires additional rotary encoders or Hall sensors. The windings of stator work in unison with the permanent magnets on the rotor to produce an almost uniform magnetic flux density in the air gap. Thus, the stator coil is directed by a persistent DC voltage (referred to as brushless DC), that switches directly from one stator coil to the other to produce a trapezoidal shaped voltage waveform %20Fundamentals.pdf ). c. AC Induction Motor (ACIM) A sinusoidal alternating current flow via the stator to produce a variable rotating magnetic field which causes a current in the rotor (usually built of a non-ferrous metal material). The induced current that circulates in the bar of the rotor which produces a magnetic field. These two magnetic fields run at different frequencies (usually the omega-s> ω-r of the motor) and generate torque. Fig 1(c)shows the motor layout %20Fundamentals.pdf). d. Permanent Magnet Synchronous Motor (PMSM) PMSM motors have some resemblance to BLDC motors, but are made to run by sinusoidal signals by which lower torque ripple is achieved. The sinusoidal conveyance of the multiphase stator windings produces a flux density which is sinusoidal that is different from the trapezoidal flux density of the BLDC motor in the air gap. However, newer design can be achieved by this sinusoidal flux density through a concentrated stator winding and an improved rotor structure. The position of rotor magnet can significantly change the electrical characteristics of the PMSM. The rotor magnet is mounted on the surface with the result that the torque ripple is small and the magnet is buried Inside the rotor structure increases the significance, thereby increasing the reluctance torque motor %20Fundamentals.pdf). The structure of the PMSM is shown in fig 1(d). EV considerations The choice of electric vehicle propulsion system depends mainly on the driver's expectations which is defined by the driving characteristics, including acceleration, top speed, acclivity, braking and range Vehicle constraints Depend on vehicle type, vehicle weight and payload. Energy source depends on batteries, fuel cells, capacitors, flywheels and a variety of hybrid power sources. The process of identifying the preferred features and packaging options for power advance must be made at the system level. The interaction between the subsystem and the possible impact of the system trade-off must be checked. Concept of EV motors The use of motors for EV application is quite different as considered to typical application scenario, as it often requires recurrent start / stop, intense acceleration / retardation, excessive torque reduced speed climbing, flat torque high speed cruising and extended operating ranges, while industrial motors are often optimized for rated conditions. Therefore, EV motors are unique, so they should be formed as a separate class. In addition to meeting the above specific requirements, EV motor design also complies on the electric vehicle system technology. From a technical point of view, the following key issues should be considered: 1. single motor or multi motor configuration 2. fixed or variable transmission 3. gear or gearless 4. system voltage Integrated motor and converter, controller, transmission and energy integration is the primary focus. EV motor designers must be completely aware of the characteristics of these components, so in this given environment design of the motor. And the normal industrial drive under the standard power supply of ordinary standard motor is completely different (Chan, C.C. and Chau, K.T, 2001). D. MOTOR SELECTION FOR EV APPLICATION The inherent advantages of BLDC give it more competitive edge over other motors with low inertia, excessive torque, and extended speed range.it exhibits efficient thermal features, high efficiency and increased power density than regular DC motors (S. K. Pillai, 2007). The miniature size has resulted in compromise in its weight and high speed range is attainable due to the absence of brushcommutator arrangement. Lack of electrical and frictional losses provides longer service life; absence of brushes and mechanical commutator make the BLDC motor almost maintenance-free and reduced EMI and noise. Highly recommended for unsafe environments (dirt, oil, grease and other foreign objects), because they can be enclosed completely. Operative features comprise of high speed, overload, high torque control, short periods of action and high acceleration and deceleration ability.

4 Chethan and Abhijith 121 The superior performance features like low inertia and quick response of the BLDC motor is the result of rotor design and special permanent magnets used. Very common reason for rotor design of the BLDC motor is to connect the permanent "magnetic field" magnets axially to the rotor shaft in a cylindrical or salient pole structure. The armature coil of the motor is mounted on the stator housing core (Dale R. Patrick and Stephen W. Fardo, 2000). Comparing BLDC motors with other motor types ( Products/Documents/appnotes/Brushless%20DC%20Mot or%20fundamentals.pdf) BLDC motor challenges The cost of the BLDC motor and associated complexity in design of the controller was the main hindrance for extensive use of BLDC as a mechanical source, however with the more advancement in electronics and embedded technology the cost and complexity is reduced which has augmented (Machine Design Magazine. Brushless DC Motors. Penton Media, Inc., 2012) the use of BLDC motors in all the fields like medical, computers, automotive and domestic applications.

5 Int. Res. J. Power Energy Engin. 122 The use of rare-earth magnets in BLDC motors has increased the performance-to-cost ratio of motors (Jacek F. Gieras, Rong-Jie Wang and Maarten J. Kamper. Axial Flux Permanent Magnet Brushless Machines. Springer, Page 96). Selection of motor rating based on Vehicle Design data The steps to choose a BLDC Motor capable of producing enough torque to propel the example Vehicle ( are discussed below. The various design data of a vehicle are listed below: GVW: Gross Vehicle Weight (Vehicle + Passenger) = 1310 Kgs.RW: Radius of wheel: 14 inches. Vmax: Desired Top Speed: 85 km/h (23.6 m/s). ta: Desired Acceleration Time: 10 s. α: Maximum incline angle: Gear ratio of 8.64:1 Step 1; Rolling Resistance (RR) force required to move a vehicle over a surface RR[N] = GVW[N] * Crr (1) Where Crr= Rolling resistance co-efficient (car tires on asphalt=0.013) RR[N] = 1310*9.8* 0.031= N Step 2: Grade Resistance (GR) force required to move a vehicle against a slope. GR[N] = GRW[N]*Sin(α) (2) GR[N] = 1310*9.8*Sin (10.5)= 2.34 KN Step 3: Accelerating Force (FA) the force requires to bring the vehicle to maximum speed from rest. GVM[M]*V m MAX s FA[N] = (3) 9.81 m 2 *t a(s) s FA[N] = = 3.1KN Step 4: determining the effect of drag force Fd on the vehicle (Chan, C.C. and Chau, K.T, 2001). Fd= 0.5 * ρ * Cd * A * (V + Vo) 2 (4) Where ρ = Air Density 1.23 kg/m 3 Cd = Aerodynamic Drag Co-efficient (for passenger car the is 0.2) A = Frontal Area m 2 ( Assuming 4 m 2 of width) V = Vehicle Velocity m/s (assuming 85Km/h=11.1 m/s) Vo = Head Wind Velocity m/s (assuming 5 Km/h=1.38 m/s) Step 5: Total Tractive Effort TTEis sum of all the obtained results TTE = RR + GR + FA+Fd TTE = TTE = 5.92 KN Step 6: Determine Torque required to accelerate the vehicle from rest (Mehrdad Ehsani, 2002). TW [N - m] = TTE* RW[M] * RF [-] (5) Where TW [N - m] = Wheel Torque RW[M] = radius of the Wheel RF = Co-efficient of rolling friction (0.01 for ordinary cars on asphalt) TW [N - m] = 5920 * 0.36 * 0.01*9.8 = N-m Step 7: Motor torque [MT] to be developed by the electric motor to accelerate the car from rest. Considering the gear ratio of 8.64:1 ( and including additional of 5 % for un accounted losses. MT = (TW [N - m] *1.05*) /8.64(6) MTT= (208.8*1.05)/8.64 MTT = 25.4 N m Step 8: Motor selection After obtaining the above result we refer the BLDC motor manual for selecting the motor with required torque and speed. There are number of models of BLDC motors are available for this application out of which we are choice is for Type: 72V3000W and Type: 48V3000W these models run at a speed of Speed: rpm and generate a Rated torque:10 N.m and Peak torque: 25 N.m ( china.com/product/dsxjarqmyfwu/china-ce-approved- 3kw-5kw-10kw-20kw-BLDC-Motor-for-Electri-Car- Motorcycle-Boat-Go-Carts.html). SIMULATION RESULTS A specific sequence of control signals is generated by sensing the rotor position of BLDC motor using hall sensors embedded in the motor, these signals are used to control the inverter module which further controls the operation of BLDC motor. Simulation is carried out in MAT lab Simulink environment for generating the control signals and the results are shown as below. Fd= 0.5 * 1.23 * 0.2 *4 * ( ) 2 Fd = 307 N

6 Chethan and Abhijith 123 Fig 2. Matlab Simulink Model of BLDC Motor and Switching Sequence Circuit Fig 3. Simulation Results: Hall Sensor Signals Fig 5. Simulation Results: Stator Current Fig 4. Simulation Results: Switching Sequence Waveforms Fig 6. Simulation Results: Stator Back EMF

7 Int. Res. J. Power Energy Engin. 124 Fig 7. Simulation Results: Rotor Speed in rpm & Electromagnetic Torque CONCLUSION REMARKS A review of some of the motors used for EV applications are compared with respect to EV considerations. This paper throws light on the design considerations and procedural steps to be followed for selection of motor for EV applications. This paper can be referred for basic design of different type of EV applications. REFERENCES Chan C.C, Chau, K.T (2001). Modern Electric Vehicle Technology, 1st ed.; Oxford University Press: New York, NY, USA, pp Dale R. Patrick and Stephen W. Fardo (2000). Industrial Electronics: Devices and Systems, Second Edition. CRC Press, page 610. Herman, Stephen L (2010). Industrial Motor Control. 6th ed. Delmar Cengage Learning. Page 1 china.com/product/dsxjarqmyfwu/china-ce- Approved-3kw-5kw-10kw-20kw-BLDC-Motor-for- Electri-Car-Motorcycle-Boat-Go-Carts.html. a.pdf roducts/documents/appnotes/brushless%20dc%20m otor%20fundamentals.pdf roducts/documents/appnotes/brushless%20dc%20m otor%20fundamentals.pdf Husain and Iqbal (1964). Electric and hybrid vehicles: design fundamentals. ISBN (alk. paper) 1. Jacek F. Gieras, Rong-Jie Wang and Maarten J. Kamper (2008). Axial Flux Permanent Magnet Brushless Machines. Springer. Page 96. Machine Design Magazine (2012). Brushless DC Motors. Penton Media, Inc. Mehrdad Ehsani. Modern electric, hybrid electric, and fuel cell vehicles: fundamentals, theory, and design/ page S. K. Pillai (2007). A First Course On Electrical Drives. New Age International,. Page 184. U.A.Bakshi and M.V.Bakshi (2009). Electrical Drives And Control. 1st ed. Technical Publications Pune,. Page 1-1 U.A.Bakshi and M.V.Bakshi (2009). Electrical Drives And Control. 1st ed. Technical Publications Pune. Page 1-1 Accepted 23 October, 2017 Citation: Chethan S and Abhijith Singh S (2017). Assessment of BLDC Motor for EV Application Considering Vehicle Design Strategy. International Research Journal of Power and Energy Engineering, 3(2): Copyright: Chethan and Abhijith. This is an openaccess article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.