International Journal of Research and Engineering
Volume 2, Issue 1
MODELING OF SEPIC FED PMBLDC MOTOR FOR TORQUE RIPPLE
MINIMIZATION
N.Lakshmipriya
S.Manivel
N.Sadeesh
M.E.,Assistant Professor
Department of EEE
Jay Shriram Group of Institution,
Tirupur, India
lakshmipriyame09@gmail.com
M.E.,Assistant Professor
Department of EEE
Jay Shriram Group of Institution
Tirupur, India
manivelee0719@gmail.com
M.E., Assistant Professor
Department of EEE
Jay Shriram Group of Institution
Tirupur, India
nsadeesh@gmail.com
Abstract— BLDC Motor suffers from commutation
torque ripple, which mainly depends on stator winding
impedance, speed and transient line current in the
conduction interval. This paper describes a novel circuit
topology and a dc input link voltage control strategy to
keep incoming and outgoing phase currents changing at
the same rate during commutation interval. A SEPIC
(single-ended primary inductor converter) and a switch
selection circuit are employed in the front of the inverter.
The desired commutation voltage is obtained by the
SEPIC converter. The input dc link voltage control
strategy is carried out by the switch selection circuit to
separate two procedures, adjusting the SEPIC converter
and regulating speed. The commutation torque ripple is
analyzed, and introduced the way to obtain the desired
dc link voltage in detail. Finally, simulation and
experimental results show that, compared with
conventional and the proposed method can obtain the
desired voltage is obtained and minimize commutation
torque ripple more efficiently.
Keywords- Brushless DC Motor, Torque ripple,
SEPIC Converter
I. Introduction
BLDC Motor is a type of Synchronous Motor. This
means magnetic field generated by the stator and magnetic
field generated by the rotor rotates at the same frequency.
DC motor also known as electronically commutated is
synchronous electric motors powered by direct current
electricity and having electronic commutation systems,
rather than mechanical commutators and brushes. The
current-to-torque and voltage to speed relationships of
BLDC motors are linear. THE brushless dc motor
(BLDCM) has been widely used in industrial fields that
require high reliability and precise control due to its simple
structure, high power density, and extended speeding range
[1]–[3]. The performance of such motors has been
significantly improved due to the great development of
power electronics, microelectronics, magnetic performance
of magnets, and motion control technology in recent years
[4]–[9]. BLDC motors may be described as stepper motors
with fixed permanent magnets and possibly more poles on
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the stator than the rotor. The latter may be without
permanent magnets, just poles that are induced on the A
SEPIC is similar to a traditional buck-boost converter, but
has advantages of having non-inverted output (the output
has the same voltage polarity as the input), using a series
capacitor to couple energy from the input to the output (and
thus can respond more gracefully to a short-circuit output),
and being capable of true shutdown. When the switch is
turned off, its output drops to 0 V, following a fairly hefty
transient dump of charge when such large horsepower drives
are needed [10]-[11]. SEPIC converter and a switch in series
with each phase are proposed for driving a permanent
magnet brushless dc motor. The SEPIC converter is
designed to operate in the discontinuous conduction mode
for operation with an ac supply. In this operation mode, the
line current follows the line voltage waveform to a certain
extent. The dc link voltage control strategy is carried out by
the switch selection circuit to separate two procedures,
adjusting the SEPIC converter and regulating speed
The paper is organized as follows DC link voltage
control strategy to keep incoming and outgoing phase
currents changing at the same rate during commutation to
control of torque ripple. The desired commutation voltage is
accomplished by the SEPIC (Single-Ended Primary Inductor
Converter). SEPIC converter and a switch in series with
each phase are proposed for driving a permanent magnet
brushless dc motor. The SEPIC converter is designed to
operate in the discontinuous conduction mode for operation
with an ac supply. In this operation mode, the line current
follows the line voltage waveform to a certain extent. The dc
link voltage control strategy is carried out by the switch
selection circuit to separate two procedures, adjusting the
SEPIC converter and regulating speed.
II. BRUSHLESS DC MOTOR
The extraction of torque and ripple requires the
mathematical model. In three phases stators winding the
phase variable are given.
[v] [ R][i ] p[ L][i] [e]
(1)
Where vectors,
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International Journal of Research and Engineering
[v]T
[va vb vc ],
[i]T
[ia ib ic ]
[e]T
[ea eb ec ]
Number of Pole
[ R]
La
0 R 0 , [ L]
0 0 R
Lba Lb Lcb
Lca Lcb Lc
:
6poles
III. DESIGN OF SEPIC CONVERTER FEED WITH
BLDC MOTOR
The proposed converter with four controlled
switches and diode the frontend consists of a SEPIC dc/dc
converter comprised of inductors L1 and L2, switch S1,
intermediate capacitor C1, diode DA and output capacitor C2.
.
Here the resistance and inductances are given by
R 0 0
Volume 2, Issue 1
Lba Lca
Assuming a symmetrical structure of the inductance
La
Lb
Lca
Lcb
Lc
L
M
[v] [ R][i ] P[ L][i ] [e]
where
L
M
M
[ L' ]
M
L
M
Figure 1.show that Circuit Diagram of SEPIC Converter
M
M
L
In three phase system without a neutral
Ia+Ib+Ic=0,hence the motor current equation may be written
The set of differential equations mentioned defines the
developed model in terms of the variables and times as an
independent variable. The torque ripple is generated due to
the current ripple. This current ripple is depends on the
stator winding impedance and back electromagnetic force.
P[ L 1 ] [ L'' ] 1{[V ] [ R][i] [e]}
where,
1
[ L'' ]
1
(L M )
0
0
1
0
0
0
(l M )
0
1
(L M )
The electromagnetic torque (Te), is
Te
ea * i a
eb*ib
ec*ic Wm
(2)
The motion equation of the BLDC motor,
dwt d t
Te
T1
B
t
J
(3)
1. SPECIFICATION OF BLDC MOTOR
The diodes DA, DB and Dc serve to free wheel the
winding currents when the switches are turned off during
current regulation and phase commutation. The output of the
converter is used to energize the three phases of the motor,
and the for proper demagnetization of the phase after each
conduction interval and to prevent conduction during
periods of negative back-EMF, the instantaneous value of
VC1 should be greater than the peak value of the back-EMF,
voltage of capacitor C1 is used to demagnetize the phases
during turn-off and for current control.
VC1>E
By applying Kirchhoff’s voltage law to the SEPIC
front-end, we obtain
VIN=VL1+VC1+V12
Since the average voltages in the two inductors are
zero, we get
VIN=VC1
Emax=Vin assuming that the ripple in the
intermediate capacitor voltage is negligible. The maximum
operating speed is then given by Ω max=Vin/Ke, where Ke is
the phase back-EMF constant of the motor. The front-end
SEPIC converter can be designed for operation either in the
continuous conduction mode
in the discontinuous
conduction mode. In CCM, its voltage conversion ratio is
given by
Where, D is the duty cycle of the switch S1 in
DCM, its voltage conversion ratio is given by
The machine details of BLDC motor are given below.
11
Rated Power
: 60W
Rated Voltage
: 48V DC
Rated Speed
:
4500rpm
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
Where, K=2L1L2/RT(L1+L2) ,R being the
equivalent load resistance and T the time period of switch S 1
.The boundary value of K between continuous and
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International Journal of Research and Engineering
Volume 2, Issue 1
discontinuous conduction modes, Kcrit can be calculated
(m=md) as
Kcrit = (1-D) 2
The converter operates in CCM when K > Kcrit and
in DCM when K < Kcrit. In both modes of operation, Vdc can
be regulated at a value higher (Boost operation) or lower
(Buck operation) than the input voltage Vin. From the
controls viewpoint, it is advantageous to have the converter
operating in the same mode under all load conditions.
IV. SIMULATION RESULTS
In this chapter describes mathematical model of
BLDC motor, and simulation model of SEPIC converter,
this mathematical model can be converter in to electrical
model by using Laplace transform. With the use of this
proposed method to get sinusoidal waveform and torque
ripple can be reduced.
Figure 2.show that modeling of BLDC with SEPIC
converter
In brushless dc motor, the armature current is
commutated; the current ripple is generated due to the stator
winding inductance and deviation of back electromagnetic
force. The torque ripple is generated due to the current
ripple. This current ripple is depends on the stator winding
impedance and back electromagnetic force
Figure 3.show that Back EMF of BLDC Motor
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International Journal of Research and Engineering
Volume 2, Issue 1
Figure 4.show that Voltage Waveform of BLDC Motor
Fig.6 show that Output Voltage for Three Phase Inverter
The current ripple can be reduced by supplying the
appropriate magnitude of input voltage for free-wheeling
period. This consists of lot of distortion. The torque ripple is
generated due to the current ripple. This current ripple is
depends on the stator winding impedance and back
electromagnetic force.
The three phase current of Input voltage varying
method for brush less dc motor has been simulated. At
starting time the distortion is high. When 0.02 sec, the
distortion will be reducing. The current ripple can be
reduced by maintaining current constant in freewheeling
region. If the current of phase b is constant when the
commutation is occurred from phase C to phase A, the
current ripple is not produced.
V. HARDWARE SETUP
FPGA based sensor control of brushless DC motor
in minimizing the harmonics caused by torque ripple in the
system. Here the SEPIC Converter is introduced between
inverter and rectifier. For the proper commutation and
control of the BLDC motor an FPGA controller is used in it.
Figure 5.show that Torque and Speed waveform of BLDC
Motor
This pulsating torque will be reduced by input
voltage varying method. The figure 5 shows that rotor speed
torque characteristics of BLDC motor. The wave form is not
uniformly in nature.
Figure 6. Block Diagram of Hardware Setup
The single phase 230 volt AC supply is fed to the
rectifier. It is converted into dc using the rectifier and fed as
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ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
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International Journal of Research and Engineering
Volume 2, Issue 1
input to the SEPIC converter. SEPIC converter fed to the
MOSFET inverter, Inverter switches are controlled by using
the FPGA controller and driver through Optoisolator, which
fed to BLDC motor. FPGA consists of gates circuit, which
fed to driver circuit. Separate supply is fed to the processor
and embedded C program is fed to generating PWM pulses.
Power Supply is the device that transfers electric power
from a source to a load using electronic circuits
Figure 8.shows that Output Voltage Waveform of Inverter
The three phase output voltage waveform of
voltage source inverter is taken from digital analyzer, In
inverter operation, if the switching angels calculated for the
equal-dc-source case is applied to the considered unequal
case. Obviously, by effectively solving the harmonics
elimination problem with large number of switching angles,
the SHE-PWM method can generate high-quality voltage
waveforms as well as less switching frequency as compared
to other modulation technique.
Figure 7.shows that Experimental Setup of Hardware
VI. HARDWARE RESULTS
The proposed SEPIC converter based scheme for
BLDC Motor drive is experimentally implemented using
FPGA controller board IR2110 for a laboratory 60W BLDC
Motor. The hardware result from the prototype such as input
and output voltage waveforms, current waveform and
Harmonics waveform are shown below. Hardware prototype
mainly consists of inverter series with SEPIC converter fed
BLDC motor. In this chapter held on different conventional
waveforms and proposed waveforms, these waveforms are
obtained by Digital Analyzer. Torque ripple can be
calculated by compare conventional method to proposed
method.
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ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
Figure 9.shows that Output Combined Voltage Waveform of
Inverter
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International Journal of Research and Engineering
Volume 2, Issue 1
Figure 12.Show that Phase Current of BLDC Motor without
SEPIC Converter
Figure 10.Shows that Output Combined Current Waveform
The dc link voltage control strategy is carried out by
the switch selection circuit to separate two procedures,
adjusting the SEPIC converter and regulating speed. In this
project SEPIC converter series with inverter fed BLDC
motor Compared with the existing method, the proposed
method can obtain the desired voltage much faster and
minimize commutation torque ripple more efficiently at both
high and low speeds.
of Inverter
The phase voltage consists of distortion due to turn
on and turn off of switching process (certain change in
current). The voltage ripple can be reduced by SEPIC
converter.
Figure 13.Show that Phase Voltage of BLDC Motor with
Figure 11.Show that Phase Voltage of BLDC Motor without
SEPIC Converter
SEPIC Converter
The required torque can be produced by the initial current
constant. When armature current is commutated, the current
ripple is generated due to the stator winding inductance and
deviation of back EMF. The current ripple leads to
generation of torque ripple. BLDC motor does not make
constant speed.
Figure 14.Show that Phase Current of BLDC Motor with
SEPIC Converter
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International Journal of Research and Engineering
By compare from without SEPIC converter, the
phase current consists of lower distortion. Phase Current of
BLDC Motor can be obtained from Digital storage
oscilloscope. DC link voltage control strategy to keep
incoming and outgoing phase currents changing at the same
rate during commutation to control of torque ripple. The
desired commutation voltage is accomplished by the SEPIC
(single-ended primary inductor converter) converter.
VII. CONCLUTION
Compared to conventional Torque ripple control
method, SEPIC converter based method will lead to lower
torque ripple. As a result, using the SEPIC converter based
input voltage varying method of brushless dc motor will
lead to increased efficiency. A new circuit topology and
control strategy has been proposed to suppress commutation
torque ripple of BLDCM. In this paper a SEPIC converter is
placed at the input of the inverter, and the desired dc link
voltage can be achieved by appropriate voltage switch
control. The switch control separates the two procedures,
adjustment of SEPIC converter, and regulation of speed so
that torque can respond immediately during transient.
REFERENCES
[1] Y.-C. Son, K.-Y. Jang, and B.-S. Suh, “Integrated
MOSFET inverter module of low-power drive system,”
IEEE Trans. Ind. Appl., vol. 44, no. 3, pp. 878–886,
May/Jun. 2008.
[2] A. Sathyan, N. Milivojevic, Y.-J. Lee, M.
Krishnamurthy, and A. Emadi, “An FPGA-based novel
digital PWM control scheme for BLDC motor drives,”
IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3040–
3049,Aug. 2009.
[3] Anandsathyan, (2009)“A Alaincassat, (2009) “New
Torque Control Method for Torque Ripple
Minimization of BLDC Motors with Un-Ideal Back
EMF,’’ IEEE Transaction Industrial Electronics., vol.
37, no.4, pp. 8/1–8/4.
[4] New
Approach
for
Minimum-Torque-Ripple
Maximum-Efficiency Control of BLDC Motor,” IEEE
Transaction Industrial Electron., vol. 48, no. 6, pp.
1065–1073,
[5] Cheng Tsung Lin, (2005) “Presented Direct Torque and
Indirect Flux Control of Brushless DC Motor’’, vol. 18,
no. 6, pp. 1365–1375, Nov. 2005.
[6] Damodhan, (2010) “A Current Control Scheme with an
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[7] Doo-Hec Jung,(2012) “Torque Ripple Minimization in
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[8] Haifeng Lu, (2004) “BLDC Motor Stator and Rotor
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Schemes and 3-D FEM Analysis,” IEEE Transaction.
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Biography
Mrs.N.Lakshmipiya completed her bachelor’s Degree in
Electrical and Electronics Engineering in Sri Ramakrishna
Engineering College, Coimbatore and Post Graduate in
Applied Electronics from Maharaja Engineering College.
She is currently working as an Assistant Professor in the
Department of Electrical and Electronics Engineering in Jay
Shriram Group of Institution, Tirupur
Mr.S.Manivel completed his bachelor’s degree in Electrical
and Electronics Engineering in Arunai College of
Engineering, Tiruvannamali and Post graduate in power
Electronics and Drives from KSR College of Technology,
Tiruchengode with GOLD medal. He is currently working
as an Assistant Professor in the Department of Electrical and
Electronics Engineering in Jay Shriram Group of Institution,
Tirupur.
Mr.N.Sadeesh received the Bachelor of Engineering in
Electrical and Electronics Engineering from Velalar College
of Engineering and Technology, Thindal, Erode in 2009.,
and the Master of Engineering degree in Control and
Instrumentation Engineering from Kongu Engineering
College, Perundurai, Erode in 2013. He is currently working
as an Assistant professor in the Department of Electrical and
Electronics Engineering in Jay Shriram Group of
Institutions,
Tirupur.
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