International Journal of Electrical and
Electronics Engineering Research (IJEEER)
ISSN 2250-155X
Vol. 3, Issue 1, Mar 2013, 169-174
© TJPRC Pvt. Ltd.
EMBEDDED FOUR SWITCH THREE PHASE INVERTER FED
INDUCTION MOTOR DRIVE
RAJU YANAMSHETTI1 & SANDEEPKUMAR KULKARNI2
1
2
E & CE Dept., PDACE, Gulbarga, Karnataka, India
E & E Dept., PDACE, M.Tech, Power Electronics, Gulbarga, Karnataka, India
ABSTRACT
The objective of the paper is to develop a microcontroller controlled four switch three phase inverter (FSTPI) to
drive three phase induction motor with minimum hardware. This inverter uses four switches instead of conventional six
switches, it has lesser switching losses, lower electromagnetic interference (EMI), less complexity of control algorithms,
robust control and reduced circuit complexity. Controller DSPIC2010 is used to generate the switching pulses for FSTPI to
drive 1 hp three phase induction motor.
KEYWORDS: Four Switch Three Phase Inverter (FSTPI), Pulse Width Modulation, Peripheral Interface Controller
(PIC), Induction Motor, Pulse Width Modulation (PWM)
INTRODUCTION
Induction motor drives are work horse of industries these drives being highly robust, easy to design, compact,
maintenance free and generally have good efficiency. AC induction motors, which contain a cage, are very popular in
variable-speed drives [1]. Such drives involve inverters which generally consist of conventional six switch three phase
inverter. The cost of these inverters is significant ally large for larger rating induction motor. Reduction in cost is due to
reduction in the number of power switches, dc power supplies, switching driver circuit losses are the main features of this
topology. It results in the possibility of the four-switch configuration instead of the six switches [5].
Now a days lot of research efforts have been directed towards development of power converters with reduced
losses and cost for driving induction motor. Among them the Four Switch Three Phase Inverter was introduced with four
IGBT switches instead of standard six switches [2]. Increasing use of microcontroller in power electronics it is possible to
control the pulse signals to control the speed of induction motor. The DSPIC30F2010 microcontroller provides gate drive
pulses to FSTPI to produce variable frequency and variable applied voltage [5].
Figure 1: FSTPI Fed IM Drive
170
Raju Yanamshetti & Sandeepkumar Kulkarni
Figure 1 shows four switch three phase inverter topology, where two switches are reduced compared to the
conventional six switch, three phase inverter topology used for speed control of the induction motor in ac motor drive, third
phase of the inverter output is driven from the center tap of the capacitor.
BLOCK DIAGRAM
Starter
Step Down
Transformer
Power
Supply
3-Φ
Rectifier
FSTP Inverter
IM
Driver
Circuit
Dspic30F2010
Figure 2: Block Diagram of Inverter & Driver Circuit
Figure 2: shows that standard AC supply is converted to a DC voltage by a three phase diode bridge rectifier. A
voltage source FSTPI is used to convert the DC voltage to a Variable AC voltage. The output of FSTPI is fed to the threephase induction motor. PC is loaded with software, it consist of several modules used for different engineering
applications. The values of each block are adjusted according to the need of drive system. The generated codes are loaded
to the processor. The processor generates required pulse according to the users setting blocks in PC. The sensor output is
fed to the processor through the ADC. The generated error signal is fed to the PI controller in the processor. Based on the
output of PI controller, the processor generated the required controlled pulses for FSTPI to control the speed of the
induction motor.
OPERATION OF FSTPI
With respect to the circuit of the FSTPI fed IM drive is shown in Fig. 1 the circuit consists of S1 , S2 , S3 and S4
four IGBT switches and split capacitors C1 and C2 . The 3-phase AC supply is fed to rectifier to obtain DC voltage, this
DC voltage is provided with a capacitor filter. The FSTPI outputs are a,b,c. Two phases ‘a’ and ‘b’ are connected to the
two legs of the inverter, while the third phase ‘c’ is connected to the center point of the dc-link capacitors, C1 and C2 .The
four power switches are denoted by the binary variables S1 to S4, where the binary ‘1’ corresponds to an ON state and the
binary ‘0’ corresponds to an OFF state. The states of the upper switches (S1 , S2) and lower switches (S3 , S4) of a leg are
complementary that is S3 =1− S1 and S4 =1− S2 . The terminal voltages Vas Vbs and Vcs of a 3-phase Y-connected Induction
Motor can be expressed as the function of the states of the upper switches as follows:
Since, there is no control on the third phase, the middle point of the DC link (point C) is taken as the reference, so:
where Vas, Vbs, Vcs are the inverter output voltages, Vc is the voltage across the dc link capacitors, Vdc is the voltage across
the capacitors C1 and C2 (Vc =V dc / 2 ). In matrix form the above equations can be written as:
171
Embedded Four Switch Three Phase Inverter Fed Induction Motor Drive
Switching States and Output Phase Voltages
Table 1
Switching
States
S1
S2
0
0
0
1
1
0
1
1
Output States
Vas
-Vc/3
-Vc
Vc
Vc/3
Vbs
-Vc/3
Vc
-Vc
Vc/3
Vcs
2Vc/3
0
0
-2Vc/3
HARDWARE DESIGN
The details of the components used in this experiment are shown in the Table 2
Table 2
1
2
Components
Microcontroller
Induction motor
3
4
5
IGBT’s
Rectifier
Opto isolator
Ratings
DSPIC30F2010
1-hp, 3-Ph, 50Hz, 415V,
1500rpm, 2.2A
FGA2NB120 1200V, 25A
IN5408, 6A
TCP250
The microcontroller based control system hardware has been programmed to vary the frequency of the PWM
signal that controls the frequency of the FSTPI. The PWM module gets two inputs –duty cycle and frequency. The
frequency is configurable within the range of 45Hz to 55Hz and duty cycle can be varied from 0-100%. The PWM signals
if the MCU are applied to the gates of IGBT through the gate driver circuit. The gate driver provides isolation, low
impedance and high current supply to the drive the IGBT. By controlling the input voltage to the analog ADC the output
frequency of the Microcontroller can be controlled.
Tabular Column
Table 3: No Load Condition Output Frequency 49Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.2
0.2
0.3
0.3
0.3
0.3
Vrms
106
122
140
155
165
182
Irms
0.2
0.2
0.3
0.4
0.5
0.6
Speed(rpm)
1400
1400
1410
1420
1440
1450
Table 4: No Load Condition Output Frequency 51Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.2
0.2
0.3
0.3
0.3
0.3
Vrms
105
118
144
155
165
195
Irms
0.2
0.2
0.3
0.3
0.4
0.5
Speed(rpm)
1500
1500
1440
1430
1410
1400
172
Raju Yanamshetti & Sandeepkumar Kulkarni
Table 5: With Load 1 Kg Output Frequency 51Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.2
0.2
0.3
0.4
0.4
0.5
Vrms
108
122
140
157
165
170
Irms
1.1
0.9
0.7
0.6
0.6
0.5
Speed(rpm)
1450
1440
1420
1410
1400
1400
Table 6: With Load 1 Kg Output Frequency 49Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.2
0.2
0.2
0.3
0.4
0.5
Vrms
106
122
140
155
165
182
Irms
0.8
0.7
0.6
0.5
0.5
0.4
Speed(rpm)
1400
1350
1340
1300
1300
1280
Table 7: With Load 2Kg Output Frequency 49Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.5
0.6
0.7
0.8
0.9
1..0
Vrms
104
120
143
154
165
185
Irms
1.5
1.6
1.7
1.8
1.8
1.8
Speed(rpm)
1300
1250
1250
1230
1210
1200
Table 8: With Load 2Kg Output Frequency 51Hz
S.No
1
2
3
4
5
6
Vdc
180
220
260
280
300
320
Idc
0.6
0.7
0.8
0.9
0.9
1.0
Vrms
108
128
140
156
165
170
Irms
1.5
1.6
1.7
1.8
1.8
1.9
Speed(rpm)
1350
1340
1330
1310
1300
1300
Complete Hardware Setup
EXPERIMENTAL RESULTS
The FSTPI drive was tested with 1 hp, 3-Ph induction motor at 45 Hz to 55 Hz frequency under No load as well
as with some load. Some of the results are shown in the tabular columns.
Embedded Four Switch Three Phase Inverter Fed Induction Motor Drive
173
PWM Waveforms Observed at 50.0 Hz Output Frequency
CONCLUSIONS
A Microcontroller based PWM controlled FSTPI fed induction motor has been tested under various load
conditions. It is found that the motor operates at higher speed when operated at higher frequency for same input voltage. It
is observed that the current increases with increase in load. The same experimentations were carried out on simulation
using MATLAB SIMULINK software. The hardware implementation results were confirmed through software
simulations.
REFERENCES
1.
Blaabjerg, D.O. Neacsu, J.K. Pedersen: Adaptive SVM to Compensate DC-link Voltage Ripple for Four-switch
Three-phase Voltage-source Inverters, IEEE Transactions on Power Electronics, Vol. 14, No.4, July 1999.
2.
C.T. Lin, C.W. Hung, C.W. Liu: Position Sensorless Control for Four-switch Three-phase Brushless DC Motor
Drives, IEEE Transactions on Power Electronics, Vol. 23, No. 1, Jan. 2008.
3.
M.B.R. Correa, C.B. Jacobina, E.R.C. Silva, A.M.N. Lima: A General PWM Strategy for Four-switch Threephase Inverters, IEEE Transactions on Power Electronics, Vol. 21, No. 6, Nov. 2006.
4.
M.N. Uddin, T.S. Radwan, M.A. Rahman: Fuzzy-logic-controller-based Cost-effective Four-switch 3-phase
Inverter-fed IPM Synchronous Motor Drive System, IEEE Transaction on Industry Application, Vol. 42, No.1,
Jan/Feb. 2006.
5.
Nalin kant Mohanty, Ranganath Muthu Microncontroller Based PWM controlled Four Switch Three Phase
Inverter Fed Induction motor. Serbian Journal of Electrical Engineering m Vol7, No2, Nov 2010.