parameter determination of the bldc motor

7/22/2019 Parameter Determination of the BLDC Motor

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FAbstract-- Brushless Permanent Magnet DC (BLDC) motor

is frequently used in the drive-train component of the electric

vehicles because it has the advantages of high power density and

high efficiency. The BLDC motor, owing to their restrictive

field weakening range, is not easy to design for vehicle

application. Therefore, this paper proposes the procedure of the

parameter determination of BLDC motor for electric vehicle.

Index Terms-- BLDC motor, traction motor, parametric

design, electric vehicle.

I. INTRODUCTION

ECENTLY, due to the concern of environmental issues

and conservation of resources, electric and hybridvehicles have received the significant interest around the

world. Hybrid electric vehicles are more interesting than

electric vehicles powered only by batteries because they have

a limit at cost and size as present technology [1]-[4]. Despite

this, the electric vehicle (EV) has employed in the urban

areas as small electric passenger car. It is because of the

advantages of high power density reducing the weight of the

car, and high efficiency of longer ranges for a given battery

size. This is possible by using the Brushless Permanent

Magnet DC motor (BLDC motor) in the drive-train

component of the EV [5]. This motor is the square-wave

motor with the surface mounted permanent magnet [6].

This paper deals with a parameter determination and

verification of BLDC motor for the propulsion applications

of the electric vehicle. Since the BLDC motor has a

restrictive field weakening range, the parameter

determination of BLDC motor is applied in the designing

procedure to ensure the required specifications, which are

instant rated power and continuous rated power of the

propulsion of the electric vehicle. The proposed procedure of

the parameter determination is accomplished by coupling the

dynamic equation of the EV and the voltage equation of the

BLDC motor.

II. MODELING OF ELECTRIC VEHICLE PROPULSIONIn the electrical vehicles, the traction motor is the key

component that delivers propulsion to driven wheels.

Therefore, in order to design the traction motor, the

prediction of the vehicle propulsion in accordance with its

power characteristic is the key component and it is

accomplished by the mathematical modeling because the

speed-torque characteristic of the traction motor completely

determines the vehicle performance.

F

Y. K. Kim, is with Korea Electronics Technology Institute, Yatap-Dong, Bundang-Gu, Seongnam-Si, Korea ([email protected]).

Se-hyun Rhyu is with Korea Electronics Technology Institute, Yatap-Dong, Bundang-Gu, Seongnam-Si, Korea

In-Soung Jung is with Korea Electronics Technology Institute, Yatap-Dong, Bundang-Gu, Seongnam-Si, Korea

A. Electric Vehicle Propulsion

The first step in the performance modeling of the EV is to

produce an equation for the tractive effort. The force

propelling the electric vehicle has to overcome the following

forces [1], [5]:

Rolling resistance force:rr rr F mgm=

Aerodynamic drag force: 20.5ad dF AC vr=

Linear acceleration force:laF ma=

Angular acceleration force:

2

2wag

G

F I arh=

whererrm is the rolling resistance coefficient, gis the

acceleration of gravity, r is the air mass density

1.205 3/kg m , A is the frontal area of the EV, dC is

aerodynamic drag coefficient, v is the EV speed, m is theEV mass, a is the acceleration of the EV, G is the gear

ratio,g

h is the efficiency of the gear system, r is the tire

radius of the EV, and I is the moment of the inertia of therotor of the motor. .

The total tractive effort required to reach the accelerationa is as follows;

t rr ad la waF F F F F= + + + (1)

B. Electric Vehicle Acceleration

The second step in the performance modeling of the EV isto produce an equation for the acceleration. The acceleration

performance of the EV is usually evaluated with the time,which is used to accelerate the EV from zero speed todefined high speed with its full load.The traction power required by acceleration can be estimated

by [1], [3]-[5].

30.625 1.05acc r d dv

P mgv AC v mvdt

m= + + (2)

C. Traction Motor

The acceleration performance of the EV is usually

evaluated by the speed-torque characteristic of the traction

motor. In the case of the traction motor, at low speeds, the

maximum torque is a constant, until the motor speed reaches

a corner speedc

w after which the torque falls. In most

cases of BLDC motor, it is generally supposed that thetorque falls linearly with increasing speed, in order to

evaluate conveniently the acceleration performance [5].

In BLDC motor, however, the speed-torque characteristic

Parameter Determination of the BLDC Motorconsidering the Dynamic Equation of Vehicle

Young-kyoun Kim, Se-Hyun Rhyu, and In-Soung Jung

R

XIX International Conference on Electrical Machines - ICEM 2010, Rome

978-1-4244-4175-4/10/$25.00 2010 IEEE


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can be obtained by the voltage equation as follows [6]-[7];

abcabcabc

abcabc Edt

diM

dt

diLRiV +-+= (3)

m

ccbbaa EiEiEiTw

++

=(4)

From the above equation, it proves that the characteristics

of BLDC motor totally depend on its parameters, such as

BEMF (Back Electromotive Force), inductance, and

resistance. Especially, at the high speed, the torque does not

fall linearly because of the effect of the phase-inductance [6]-

[7].

D. Specification of the Electric Vehicle Propulsion

Specifications of the EV, which is small electric

passenger car, are obtained from a vehicle manufacturer and

summarized as follows;

- When fun driving, EV top speed in 15sec: 65 kph

Instant rated power of the traction motor: 25 kW- When normal driving, EV top speed in 30sec: 65 kph

Continuous rated power of the traction motor: 10 kW

- EV mass included passengers: 900 kg

- Frontal area of EV: 1.2 2m

- Tire radius of EV: 0.27 m

- Rolling resistance coefficient: 0.013

- Aerodynamic drag coefficient: 0.75

- Gear ratio: 12 at the fun driving, 8 at the normal driving

- Efficiency of the Gear: 97%

III. PROCEDURE OF THE PARAMETER DETERMINATION

The speed-torque characteristic of the BLDC motor variesin nonlinearity in accordance with the motor parameters.

Examples of the parameter combination are listed in Table I.

In this case, phase resistances are handled with enough big

constant, which is 0.01 ohm, because the effect of the speed-

torque characteristic in accordance with the resistance

variation is normally small in application of the traction

motor. Fig. 1 shows speed-torque characteristics under the

models of BEMF variations, and Fig. 2 shows the analysis

results of the acceleration performance of models of BEMF

variations. Fig. 3 shows speed-torque characteristics under

the models of phase-inductance variations, and Fig. 4 shows

the analysis results of the acceleration performance of

models of phase-inductance variations. In this case, theacceleration performances of the model 2 and the model 5

are sufficient, and performances of the other models are

insufficient or excessive.

In order to design the BLDC motor as the application of the

EV, it is very important to decide the suitable scope of the

BLDC motor parameters, which is corresponding to the

given specifications of the EV propulsion, and is

accomplished by computing the dynamic acceleration (2)

coupled with the electrical equation (3) and (4) [1]-[7].

Therefore, the proposed procedure of the parameter

determination is consists of two steps and the concept of this

process which is shown in Fig. 5.

0 25 50 75 100 125 150 175 2000

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0

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Speed(rpm)

Torque (Nm)

model 1model 2model 3

Current(A)

Speed-Torque

Current-Torque

Fig. 1. Speed-torque characteristics on condition of BEMF variations

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V

ehicleSpeed(km/h)

Time (sec)


Fig. 2. Speed-torque characteristics on condition of BEMF variations

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Speed(rpm)

Torque (Nm)

Model 4model 5model 6

Current(A)

Fig. 3. Speed-torque characteristics on condition of phase-inductance

variations

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20

30

40

50

60

70

80

VehicleSpeed(km/h)

Time (sec)


Fig. 4. Acceleration performance on condition of phase-inductance

variations

TABLEICOMBINATIONS OF THE MOTOR PARAMETERS

Combinationnumber

Parameters of BLDC motor

BEMF(V@1krpm)

Inductance(mH)

Resistance

(W)

Model 1 22 0.6 0.01

Model 2 19 0.6 0.01

Model 3 16 0.6 0.01

Model 4 20 0.9 0.01

Model 5 20 0.5 0.01

Model 6 20 0.1 0.01


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From the analysis results of the parameter determination

process, overall maps of the acceleration performance of the

EV on condition of the change of the BEMF and the phase-

inductance are illustrated from Fig. 6 to Fig. 11.

On the condition of instant rated power, the map of the

EV velocity in 15 second is shown in Fig. 6, the map of the

armature current is illustrated like in Fig. 7, and the map of

the corner speed of the motor is shown in Fig. 8.

On the condition of continuous rated power, the map of

the EV velocity in 30 second is shown in Fig. 9, the map of

the armature current is shown in Fig. 10, and the map of the

corner speed of the motor is shown in Fig. 11. The proper

decision of the motor parameter is accomplish by the

superposition of the maps. At the Fig. 6, the area under 65

km/h, which is the required condition of the instant rated

power, is unfeasible area of the parameter map.

From Fig. 6 to Fig. 11, the proper range of the parameter

determination is the target area, which is decided by

considering the current limitation of the motor and is

satisfied with the given condition of the EV velocity. In thecase, the current density under the continuous rated power

operation is the top priority condition to decide the target

area. The target area is bounded by two conditions. First

0.05 0.2 0.4 0.6 0.8 115

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24

25

Inductance (mH)

Ind

ucedvoltage(V@1krpm)

70

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90

95

650.05 0.2 0.4 0.6 0.8 1

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Inductance (mH)

Ind

ucedvoltage(V@1krpm)

70

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80

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95

65

70

75

80

85

90

95

65In

crea

singdire

ctio

n

TargetArea

MaximumvelocityofEV

(km/h)

Unfeasible area

Fig. 9. Velocity map in 30 sec. at continuous rated power

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)

Indu

cedvoltage(V@1krpm)

0.05 0.2 0.4 0.6 0.8 115

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75

Inductance (mH)

Indu

cedvoltage(V@1krpm)

Incre

asing

dire

ctio

n

TargetArea

Unfeasible area

Current(A)

Fig. 10. Armature current map at continuous rated power

0.05 0.2 0.4 0.6 0.8 115

16

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19

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3500

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Inductance (mH)

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cedvoltage(V@1krpm)

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)

Indu

cedvoltage(V@1krpm)

Increasingdirection

TargetArea

Unfeasible areaBasespeedofBLDCmotor(rpm)

Fig. 11. Corner speed map at continuous rated power

Fig. 5. Proposed procedure of the parameter determination

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)

Inducedvoltage(V@1krpm)

65

MaximumvelocityofEV

(km/h)

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)


65

MaximumvelocityofEV

(km/h)

Incr

easin

gdire

ctio

n

TargetArea

Under 65 km/h

Fig. 6. Velocity map in 15 sec. at instant rated power

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)


0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)


Incre

asing

dire

ctio

n

TargetArea

Unfeasible area

Current(A)

Fig. 7. Armature current map at instant rated power

0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)


0.05 0.2 0.4 0.6 0.8 115

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Inductance (mH)


Increasingdirection

TargetArea

Unfeasible areaBasespeedofBLDCmotor(rpm)

Fig. 8. Corner speed map at instant rated power


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condition is the current density below 5A/mm2, and second

condition is the required acceleration performance of the

vehicle.

IV. VERIFICATION OF PARAMETERDETERMINATION

From results of the parameter determination, a BLDC

motor was designed with parameters, shown in Table II.

At the condition of instant rated power, Fig. 12 and Fig.

13 show analysis results of the acceleration performance of

the EV.

At the condition of instant rated power, Fig. 14 and Fig. 15

show analysis results of the acceleration performance of the

EV. From the simulation results, the top speed of the EV is

over 65 km/h, on level ground.

V. CONCLUSION

This paper deals with the method and procedure of the

parameter determination of BLDC motor for an EVpropulsion applications. The proposed parameter

determination is accomplished by coupling the dynamic

equation of EV and the voltage equation of BLDC motor.

The method provides the effective way to choose the

design parameters for the BLDC motor, which is employed

for the EV.

REFERENCES

[1] Mehrdad Ehsani, Yimin Gao, Sebastien E. Gay and Ali Emadi,Modern Electric, Hybrid Electric, and Fuel Cell Vehicles, CRC Press,2005.

[2] Yee-Pien Yang and Down Su Chuang, Optimal Design and Controlof a Wheel Motor for Electic Passenger Cars, IEEE Trans. OnMagnetics, Vol. 43, No. 1, 2007, pp. 51 61.

[3] P. Joshi and A. P. Deshmukh, Vector Control: A New ControlTechnique for Latest Automotive Applications (EV),'' ICETET '08.Conference on, 2008, pp. 911-916.

[4] Y. Gao and M. Ehsani, Parametric design of the traction motor andenergy storage for series hybrid off-road and military vehicles, IEEETrans. On PowerElectronics, Vol. 21, Issue 3, 2006, pp. 749 755.

[5] J. Larminie and J. lowry, ELECTRIC VEHICLE TECHNOLOGYEXPLAINED, John Wiley & Sons, Ltd., 2003.

[6] J. R. Hendershot Jr and T. Miller, DESIGN OF BRUSHLESSPERMANENT-MAGNET MOTOR, OXFOD MAGNA PHYSIS, 1994.

[7] Cheee Mun Ong, Dynamic Simulation of Electric Machinery usingMatlab / Simulink, Prentice Hall, 1997.

VI. BIOGRAPHIES

Young-Kyoun Kim was born in Korea in 1971. He received the B.S., M.S.,

and Ph.D. degrees from Changwon National University, Changwon, Korea.

He was a Senior Research Engineer with Samsung Electronics Company,

Ltd., and he is currently a leader of Motor & Actuator team, Intelligence

and Mechatronics Research Center, Korea Electronics Technology Institute,

Korea.

Se-hyun Rhyuwas born in Korea in 1970. He received the B.S., M.S., andPh.D. degrees from Hanyang University, Seoul, Korea, and he is currently a

managerial researcher, Intelligence and Mechatronics Research Center,

Korea Electronics Technology Institute, Korea.

In-Soung Jung was born in Korea in 1970. He received the B.S., M.S., and

Ph.D. degrees from Hanyang University, Seoul, Korea, and he is currently a

director of Intelligence and Mechatronics Research Center, Korea

Electronics Technology Institute, Korea.

0 10 20 30 40 500

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VehicleSpeed(km/h)

Time (sec) Fig. 12. Acceleration of EV at instant rated power

0 10 20 30 40 50 60 700

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60

70

0

5

10

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25

30

MotorTorque&RunningResistance(Nm)

Velocity (km/h)

MotorPower(kW)

Motor torque

Running resistance of electric vehicle

Motor power

Fig. 13. Performance of motor and electric vehicle at instant rated power

0 10 20 30 40 500

10

20

30

40

50

60

70

80

VehicleSpeed(km/h)

Time (sec) Fig. 14. Acceleration of EV at continuous rated power

TABLEIIPARAMETERSPECIFICATION

Parameters Values Unit

Phase Inductance 0.235 mH

Phase Resistance 0.002 (W)

Rated Speed 3600 rpm

Back-EMF @ 1000 rpm 21.5 V

Poles / Slots 8 / 12 -

Continuous rated current @ 27Nm, 10kW 58 A

Instant rated current @ 53Nm, 25kW 120 A

0 5 10 15 20 25 30 35 40 45 50 55 60 650

5

10

15

20

25

30

35

40

0

5

10

15

20

25

30

MotorT

orque&RunningResistance(Nm)

Velocity (km/h)

MotorPower(kW)

Motor torque

Running resistance of electric vehicle

Motor power

Fig. 15. Performance of motor and electric vehicle at continuous rated power

parameter determination of the bldc motor

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