Single-Phase to Three-Phases Sinusoidal Waveform Converter
for driving 3 Phase induction motor based on SPWM Inverter
Boonruang Wangsilabatra 1, Punyapat Chofabunthit 2
1,2

Faculty of Engineering , Pathumwan Institute of Technology , Bangkok , 10330 ,Thailand

1Introduction
The 3-phases induction motor might be used for powerful
more than single-phase induction motor, because it can begiven the high power when comparison with single phaseinduction motor as the same size. But the three phaseinduction motor must be connected to the three phase supply
which have phase voltage waveform are difference and phasor
diagram that shown in Fig.1(a),(b) and can be written in theequation (1) [1].

Three- phase induction motor
Single-phase supply

Fig.2 Three-phase induction motor in single phase supply
20120240

Single phase to three phase converter
Fig. 3 is the concept for convert single phase to three phases
sinusoidal waveform; start from phase voltage Va is shift to 120°
lagging for generated phase voltage Vb. After that summing Va ,Vb together and inverse phase for generated phase voltage Vc(degree)

Inverse phase(a) Phase voltage Vb(a) Three-phases voltage waveform

180120oo

Shift phase120120ooo120o0(b) Phasor diagramo−120(b) Phase voltage Vc
Fig.3 Single-phase voltage converts to three-phase voltage
Fig.1 Three-phase voltage waveform and phasor diagram
va = Vm sin(ωt + 0°)
vb = Vm sin(ωt - 120°)(1)

2.1 Sine wave pulse width modulation inverter (SPWM)
Fig. 4 is the block diagram of the SPWM inverter [3] fordriving three-phase induction motor by using switchingfrequency about 5kHz. The function of switch S1 is start/stop forsmooth increasing and decreasing the spindle speed of motor.

vc = Vm sin(ωt + 120°)va* +Single phase vb* to three phases *vc
converterva

So that, if you want to drive three-phase induction motorby using single-phase waveform, you must be shift the phasevoltage into two-phase waveform by connect a capacitor thatshown in Fig. 3 with this connection, its look like split phaseinduction motor, the motor will continue turning on the single
phase supply but the performance of a motor is fairy poor. [2]+10V

Start+-Gate driver+-MOSFETs
orIGBTs+-300V

RT1S1StopRT2CTf s =5kHzM
3380V/220V
Y/Delta connection

Fig.4 block diagram of the SPWM inverter for driving
three-phase induction motor

The principle of softly start/stop is using the percentage ofmodulation between command reference sinusoidal waveform
and triangle waveform carrier frequency that shown in Fig.5[4].

3.4 Soft-stop when S1 change from start to stop position
Stopva*VL1 / Vsv ab

0.780.612

Square wave
mode

Non-linear mode

Fig. 9 The magnitude of va * and modulation percentage of vab
are decrease smoothly.
Linear mode01

3.24maFig.5 rms line voltage VS percentage modulation
3. Simulation result
This paper used the Proteus release 7.2 SP6 computer
program for simulation the circuits design and the result asshown below
3.1 Single-phase to three-phase converterva* vb* vc*

Fig.6 Single phase to three-phase sinusoidal waveform
3.2 Line voltage of SPWM inverterv abvbc
vca

Fig. 7 The line voltage for three-phase induction motor
3.3 Soft-start when S1 change from stop to start position

va*Startv ab

Fig. 8 The magnitude of va* and modulation percentage of vab
are increase smoothly.

Fig.6 that show the sinusoidal waveform of three-phasewhich converted from the single-phase va by using the principlein Fig.3
Fig.7 that show the line voltage for supply to three-phaseinduction motor from the SPWM inverter by the circuits which
made from the block diagram in Fig.4
Fig.8 that show the command of phase voltage va* and theline voltage vab for three-phase induction motor when switch S1change from stop to start position. The magnitude of va* andmodulation percentage of vab are smooth increasing. That mean
the rms of line voltage for driving motor and spindle speed issmooth increasing follow.
Fig.9 that show the reverse operation when switch S1change from start to stop position. The magnitude of va* andmodulation percentage of vab are smooth decreasing. That mean
the rms of line voltage for driving motor and spindle speed issmooth decreasing follow.
4. Conclusion
According to circuits design and simulation result thatshown the operation is work well and can be applied to drive thethree-phase induction motor by using only single-phasesinusoidal waveform for only synchronous spindle speed which
dependence on the frequency of single phase line voltage before
convert to three phase sinusoidal waveform. The rating of power
element such as gate driver, power MOSFETs or power IGBTs
and dc bus power supply must be in line with the rating powerof three phases induction motor.
References[1] Boonruang.W , “Three Phase Sinusoidal Waveform
Generator Circuit for Education” ,Pathumwan Academic
Journal No.2 , 2011,pp27-32[2] Naung Cho Wynn and Tun Lin naing , “Single Phase
Three Phase Converter” , World Academy of Science ,Engineering and Technology 42,2008,pp343-347[3] Muhamadh. Rashid, “Power electronics circuits,device,andapplications second edition”, Prentice-Hall International
Editions, 1993,pp372-382[4] N. Mohan, T. Underland and W. Robbins, “PowerElectronics:Converters,Applications,and design”, John
Wiley & Sons,3rd edition,2003.