CONVERSION OF SINGLE PHASE TO THREE PHASE SUPPLY

CONVERSION OF SINGLE PHASE TO THREE PHASE SUPPLY

ABSTRACT

This paper presents a simple converter topology for driving a load with a single-phase ac supply. Using only six active switch IGBT’s. The converter supplies balanced output voltages at rated frequency, the proposed topology permits to reduce the rectifier switch currents, the harmonic distortion at the input converter side, and presents improvements on the fault and control approaches are supported by test results. The converter takes single phase supply and converts it into three phase supply with the help of thyristors. The single phase supply is first converted into dc supply by using rectifier again dc supply of rectifier is given to inverter where IGBT’s are used and converts the dc supply again into three phase ac supply. The experimental result showed that sinusoidal waveform produced remained approximately constant with increase in load and the developed hardware has satisfactory converted the single phase power to three phase power supply.

Keywords:- AC to DC to AC converter, IGBTs, drive system, inverter.

INTRODUCTION

In the past, single-phase to three-phase conversion systems were made possible by the connection of passive elements capacitors and reactors with auto transformer converters. Such kind of system presents well know disadvantages and limitations. so to overcome from this disadvantages the newly adopted thyristors and power electronics devices were used mainly thyristors like SCRs, MOSFETs, GTOs etc. The project is about ‘single phase to three phase conversion system using IGBTs.

Since the beginning of the solid state power electronics, the semiconductor devices were the major technology used to drive the power processors. Looking at the semiconductor devices used in the former controlled rectifiers and comparing them with the new technologies it makes possible to figure out the astonishing development. Beyond the improvement related to power switches, it was also identified a great activity in terms of the circuit topology innovations in the field of three-phase to three-phase, single phase to single phase and three-phase to single phase conversion systems. The single-phase induction motor drives by the three-phase induction motor drives in some low-power industrial applications and. However, in some rural areas where only a single-phase utility is available, we should convert a single-phase to a three-phase supply. This paper proposes an alternative solution for phase conversion with very low overall cost, moderate motor performance during start up and high steady-state performance at line frequency.

This system fits the requirements in rural areas where only a single-phase supply is available.

 

Fig.1. BLOCK DIAGRAM

As we all know any invention of latest technology cannot be activated without the source of power. All the electronic or electrical components need power supply of AC supply .So we are converting power from single phase into three phase AC supply. Using these three phase power supply, we can drive any motor. Block diagram of converting single phase to three phase power supply consist of input, rectifier, filter, inverter, load, driving stage, microcontroller and power supply. As we seen from the block diagram the first stage is input, input is given in two circuits, first one is given to rectifier and further towards the other and the second input is given to controller stage Since the input is first works in rectifier which converts the ac supply into pulsating dc but after rectification also having some ac contain. So to remove that filters are used consisting of inductors and capacitors which helps to eliminate the ac contain and gives nearly pure dc. Further the supply is given to invertor where IGBT's are connected. In addition with main power supply again an energizing stage is there which use to energize IGBT's i.e

DRIVING STAGE

Comprises of micro controller where programs are made accordingly supply is given to invertor stage as per the programmer's and circuit requirement. Afterwards the dc supply which is fed to invertor is converted into ac supply in the form of three wire i.e three phase supply. After the conversion the three phase supply is given to load which is motto of this project means to convert single phase supply into three phase supply. In the sense of load the load may be a motor or any three phase load but in these project we use three phase lamps.

 

Fig.2. CIRCUIT DIAGRAM

The Single phase to three phase converter using IGBT for driving three-phase induction motor by using switching frequency about 7 kHz. Varying above frequency this result is smooth increasing and decreasing the spindle speed of motor Tree phase motor. The sinusoidal waveform of three-phase which converted from the single phase input of the 230 Ac rectified by bridge diodes. The gate drive circuit needs to provide an interface between the switching signals coming from the DSP waveform generator and the IGBT in the circuit. The Digital processing from MCU gives a 3.3V signal, while the waveform generators allow for a specified voltage level. The gate to source voltage needed for desired operation of the MOSFET is on a 110 DC level. In addition, the high side IGBT in this circuit do not have the source connected to ground, so the actual voltage needed to drive the gate depends on the varying voltage at the source. Switching Signal currently small motor drive systems are expensive and implement control schemes that use relatively high switching frequencies. One drawback to the high switching frequencies is the decrease in efficiency that occurs from switching loss. The control scheme has been used widely and generates little acoustic noise since the switching frequency is on the upper end of the audible acoustic range (20 Hz – 4k – 20 kHz). These control schemes also provide good dynamic performances. However, this application does not need good dynamic performance since there are no dynamic load and speed requirements.

The rating of power element such as gate driver, power IGBTs dc bus.

WORKING

As shown in above figure that the single phase 230v supply is given to the input and the rectifier circuit is connect after that to convert single phase AC to DC. The filter is connected to reduce the harmonics present in the ac and gives the pulsating

DC, the fuse is connected to protect the circuit and the resistor is connected to limit the current and then the converter circuit is connected in which the six IGBT switching device is connected to convert DC to three phase AC.

Each gate of IGBT is connected to each terminal of microcontroller. In microcontroller the embedded c program is installed and which drives the IGBT.

We are giving 230v supply to rectifier, for positive pulse two diodes are trigger and for negative another two diodes are trigger and AC supply is converted to DC. In inverting stage we are using six IGBT as inverter. Upper side three IGBT are called as positive group IGBT and lower side three IGBT are called as negative group IGBT. IGBT work in 180 degree mode of operation in which one IGBT from upper group and anther two from lower group and after that one from lower group another from upper group. Same procedure is fallow by whole inverter

circuit. diode are connect across each IGBT to limiting the reverse current flowing through the inverter. in this way we getting the three phase from middle of two IGBT.

 

Fig.3. Pin diagram

VCC : Digital supply voltage.

GND : Ground.

Port A (PA7..PA0) : Port A serves as the analogy inputs to the A/D Converter. Port A also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used. Port pins can provide internal pull-up resistors (selected for each bit). The

Port A output buffers have symmetrical drive characteristics with both high sink and source capability. When pins PA0 to PA7 are used as inputs and are externally pulled low, they will source current if the internal pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes active, even if the clock is not running.

Port B (PB7..PB0) : Port B is an 8-bit bidirectional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port B also serves the functions of various special Features

Port : Pin Alternate Functions

PB7 : SCK (SPI Bus Serial Clock)

PB6 : MISO (SPI Bus Master Input/Slave Output)

PB5 : MOSI (SPI Bus Master Output/Slave Input)

PB4 : SS (SPI Slave Select Input)

PB3 : AIN1 (Analogy Comparator Negative Input) OC0 (Timer/Counter0 Output Compare Match Output)

PB2 : AIN0 (Analogy Comparator Positive Input) INT2 (External Interrupt 2 Input)

PB1 : T1 (Timer/Counter1 External Counter Input)

PB0 : T0 (Timer/Counter0 External Counter Input) XCK (USART External Clock Input/Output)

Port C (PC7..PC0) : Port C is an 8-bit bidirectional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running. If the JTAG interface is enabled, the pull-up resistors on pins PC5(TDI), PC3(TMS) and PC2(TCK) will be activated even if a reset occurs. Port C also serves the functions of the JTAG interface and other special features

Port : Pin Alternate Function

PC7 : TOSC2 (Timer Oscillator Pin 2)

PC6 : TOSC1 (Timer Oscillator Pin 1)

PC5 : TDI (JTAG Test Data In)

PC4 : TDO (JTAG Test Data Out)

PC3 : TMS (JTAG Test Mode Select)

PC2 : TCK (JTAG Test Clock)

PC1 : SDA (Two-wire Serial Bus Data Input/output Line)

PC0 : SCL (Two-wire Serial Bus Clock Line)

Port D (PD7..PD0) : Port D is an 8-bit bidirectional I/O port with internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port D also serves the functions of various special Features

Port : Pin Alternate Function

PD7 : OC2 (Timer/Counter2 Output Compare Match Output)

PD6 : ICP (Timer/Counter1 Input Capture Pin)

PD5 : OC1A (Timer/Counter1 Output Compare A Match Output)

PD4 : OC1B (Timer/Counter1 Output Compare B Match Output)

PD3 : INT1 (External Interrupt 1 Input)

PD2 : INT0 (External Interrupt 0 Input)

PD1 : TXD (USART Output Pin)

PD0 : RXD (USART Input Pin)

RESET : Reset Input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset.

Reset Sources : The ATmega16 has five sources of reset:

• Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset threshold (VPOT).

• External Reset. The MCU is reset when a low level is present on the RESET pin for longer than the minimum pulse length.

• Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and the Watchdog is enabled.

• Brown-out Reset. The MCU is reset when the supply voltage VCC is below the Brown-out Reset threshold (VBOT) and the Brown-out Detector is enabled.

• JTAG AVR Reset. The MCU is reset as long as there is a logic one in the Reset Register, one of the scan chains of the JTAG system.

XTAL1 : Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.

XTAL2 : Output from the inverting Oscillator amplifier.

AVCC : AVCC is the supply voltage pin for Port A and the A/D Converter. It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter.

AREF : AREF is the analog reference pin for the A/D Converter.

REFERENCE

1. M. Khan, I. Husain, and Y. Sozer, “Integrated electric motor drive and power electronics for bidirectional power flow between the electric vehicle and dc or ac grid,” Power Electronics, IEEE Transactions on,vol. 28, no. 12, pp. 5774–

5783, Dec 2013.

2. Shivanagouda.B.Patil, M. S. Aspalli,” Operating Three Phase Induction Motor Connected to Single Phase Supply ,” International Journal of Emerging Technology and Advanced Engineering, ISSN 2250-2459, Volume 2, Issue 11, November 2012.

3. C. Jacobina, E. Cipriano dos Santos, N. Rocha, de Sa, B. Gouveia, and E. da Silva, “Reversible ac drive systems based on parallel ac-ac dc-link converters,” Industry Applications, IEEE Transactions on, vol. 46, no. 4,pp. 1456 –1467, July-Aug. 2010.

4. C. B. Jacobina, E. C. dos Santos Jr., N. Rocha, and E. L. Lopes Fabricio,“Single-phase to threephase drive system using two parallel single phase rectifiers,” Power Electronics, IEEE Transactions on, vol. 25,no. 5, pp. 1285–1295, May 2010.

5. Dong-Choon Lee, Member, IEEE, and Young- Sin Kim,” Control of Single-Phase-to-Three-Phase AC/DC/AC PWM Converters for Induction Motor Drives,” IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 54, NO. 2, APRIL 2007.

FOOTSTEP POWER GENERATION USING PIEZO ELECTRIC TRANSDUCERS

FOOTSTEP POWER GENERATION USING PIEZO ELECTRIC TRANSDUCERS 

 Electrical and Electronics Project by Ravi Devani

ABSTRACT

Man has needed and used energy at an increasing rate for the sustenance and well-being since time immemorial. Due to this a lot of energy resources have been exhausted and wasted. Proposal for the utilization of waste energy of foot power with human locomotion is very much relevant and important for highly populated countries like India where the railway station, temples etc., are overcrowded all round the clock .When the flooring is engineered with piezo electric technology, the electrical energy produced by the pressure is captured by floor sensors and converted to an electrical charge by piezo transducers, then stored and used as a power source. And this power source has many applications as in agriculture, home application and street lighting and as energy source for sensors in remote locations.

Keywords—Piezoelectricity, PZT, PVDF, Inverter, PIC16F873

INTRODUCTION

At present, electricity has become a lifeline for human population. Its demand is increasing day by day. Modern technology needs a huge amount of electrical power for its various operations. Electricity production is the single largest source of pollution in the whole world. At one hand, rising concern about the gap between demand and supply of electricity for masses has highlighted the exploration of alternate sources of energy and its sustainable use. On the other hand, human population all over the world and hence energy demand is increasing day by day linearly. Accordingly, it is an objective of the present invention to provide a method of electrical power generation from this ever increasing human population that does not negatively impact the environment. This technology is based on a principle called the piezoelectric effect, in which certain materials have the ability to build up an electrical charge from having pressure and strain applied to them. Piezoelectricity refers to the ability of some materials to generate an electric potential in response to applied pressure. Harvesting of energy which means energy is already available, but is going to waste if not utilized. Embedded piezoelectric material can provide the magic of converting pressure exerted by the moving people into electric current.

RESEARCH ELABORATIONS

STUDY OF PIEZO MATERIALS

Piezoelectric ceramics belong to the group of ferroelectric materials. Ferroelectric materials are crystals which are polar without an electric field being applied. The piezoelectric effect is common in piezo ceramics like PbTiO3, PbZrO3, PVDF and PZT. The main component of the project is the piezoelectric material. The proper choice of the piezo material is of prime importance. For this, an analysis on the 2 most commonly available piezoelectric material - PZT and PVDF, to determine the most suitable material was done. The criterion for selection was better output voltage for various pressures applied. In order to understand the output corresponding to the various forces applied, the V-I characteristics of each material namely, PZT and PVDF were plotted. For this the Piezo transducer material under test is placed on a Piezo force sensor. Voltmeters are connected across both of them for measuring voltages and an ammeter is connected to measure the current. As varying forces are applied on the Piezo material, different voltage readings corresponding to the force is displayed. For each such voltage reading across the force sensor, various voltage and current readings of the Piezo test material are noted.

 

Fig 1: V-I graph of PVDF material

 

Fig 2: V-I graph of PZT

 The voltage from PZT is around 2 V where as that of PVDF is around 0.4V.We can thus conclude that better output is obtained from the PZT than the PVDF.

STUDY OF CONNECTIONS

Next to determine the kind of connection that gives appreciable voltage and current necessary, three PZT are connected in series.

 

Fig .3: PZT in series connection

Electrical and Electronics Project by Ravi Devani

A force sensor and voltmeter is connected to this series combination. As varying forces are applied on this connection, corresponding voltages are noted. Also the voltage generated across the series connection and the current is measured. Similarly the connections are done for parallel and series-parallel connections are done and the graphs are as in figures 3 and 4.

 

Fig 4: V-I graph of parallel and series connection

 

Fig 5: V-I graph of parallel and series combination

It can be seen from the graph that the voltage from a series connection is good but the current obtained is poor, whereas the current from a parallel connection is good but the voltage is poor. But this problem is rectified in a series- parallel connection where a good voltage as well as current can be obtained.

HARDWARE IMPLEMENTATION

The hardware set up is as shown in figure 6. A tile made from piezo material is made. The voltage generated across a piezo tile is supplied to a battery for it to recharge and supply the dc loads. Voltage generated is also given to an inverter, from where it is supplied to all the ac loads. A LCD is interfaced to the tile using a PIC microcontroller to display the voltage generated across the piezo tile.

 

Fig 6: Hardware setup

WORKING

The piezoelectric material converts the pressure applied to it into electrical energy. The source of pressure can be either from the weight of the moving vehicles or from the weight of the people walking over it. The output of the piezoelectric material is not a steady one. So a bridge circuit is used to convert this variable voltage into a linear one. Again an AC ripple filter is used to filter out any further fluctuations in the output. The output dc voltage is then stored in a rechargeable battery. As the power output from a single piezo-film was extremely low, combination of few Piezo films was investigated. Two possible connections were tested - parallel and series connections. The parallel connection did not show significant increase in the voltage output. With series connection, additional piezo-film results in increased of voltage output but not in linear proportion. So here a combination of both parallel and series connection is employed for producing 40V voltage output with high current density. From battery provisions are provided to connect dc load. An inverter is connected to battery to provide provision to connect AC load. The voltage produced across the tile can be seen in a LCD. For this purpose microcontroller PIC16F873A is used. The microcontroller uses a crystal oscillator for its operation. The output of the microcontroller is then given to the LCD which then displays the voltage levels.

 

Fig 7: Schematic representation of the working model

The inverter used in this circuit uses the IC CD4047. It is used to convert the DC voltage stored in the battery to AC voltage. IC CD4047 produces two pulse trains phase shifted by 180°. These pulse trains are used to switch transistors configured in common emitter mode producing pulse trains of 12V, which is capable of switching a MOSFET. The sources of the two MOSFETs used in the inverter circuit are supplied with a 12V supply. When the MOSFETs are switched on by the outputs of the transistors, two output pulses of 12V are obtained. These pulses are connected to a step up transformer from whose high voltage side; we obtain the 220V AC supply.

MAXIMUM THEORETICAL VOLTAGE GENERATED

When a force is applied on piezo material, a charge is generated across it. Thus, it can be assumed to be an ideal capacitor. Thus, all equations governing capacitors can be applied to it. In this project, on one tile, we connect 3 piezo in series.10 such series connections are connected in parallel. Thus when 3 piezoelectric discs are connected in series, its equivalent capacitance becomes: 

thus,                 

(1) We know, (2) So, (3) Hence, (4) Thus , (5) Hence, the net voltage generated in series connection is the sum of individual voltages generated across each piezoelectric disc. Output voltage from 1 piezo disc is 13V. 

Thus, Veq  = V1+V2+V3                        (6) 

                   = 13+13+13 

                   = 39V 

Thus the maximum voltage that can be generated across the piezo tile is around 39V.

ANALYSIS DONE ON THE PIEZO TILE

People whose weight varied from 40kg to 75 kg were made to walk on the piezo tile to test the voltage generating capacity of the Piezo tile. The relation between the weight of the person and power generated is plotted in figure 8. From the graph it can be seen that, maximum voltage is generated when maximum weight/force is applied. Thus, maximum voltage of 40V is generated across the tile when a weight of 75 Kg is applied on the tile. 

Fig 8: Weight V/s power graph of piezo tile

CONCLUSION

A piezo tile capable of generating 40V has been devised. Comparison between various piezo electric material shows that PZT is superior in characteristics. Also, by comparison it was found that series- parallel combination connection is more suitable. The weight applied on the tile and corresponding voltage generated is studied and they are found to have linear relation. It is especially suited for implementation in crowded areas. This can be used in street lighting without use of long power lines. It can also be used as charging ports, lighting of pavement side buildings.

REFERENCES

[1] Vibration Based Energy Harvesting Using Piezoelectric Material,M.N. Fakhzan, Asan G.A.Muthalif, Department of Mechatronics Engineering, International Islamic University Malaysia, IIUM,Kuala Lumpur, Malaysia.

[2] Piezoelectric Crystals: Future Source Of Electricity, International Journal of Scientific Engineering and Technology, Volume 2 Issue 4, April 2013Third Year

Electronics Engineering, Atharva College of Engineering, Mumbai, India.

[3] Electricity from Footsteps, S.S.Taliyan, B.B. Biswas, R.K. Patil and G. P. Srivastava, Reactor Control Division, Electronics & Instrumentation Group And T.K. Basu IPR, Gandhinagar.

[4] Estimation of Electric Charge Output for Piezoelectric Energy Harvesting,LA-UR-04-2449, Strain Journal, 40(2), 49-58, 2004;Henry A. Sodano, Daniel J. Inman, Gyuhae Park.

[5] Center for Intelligent Material Systems and Structures Virginia Polytechnic Institute and State University.

[6] Design Study of Piezoelectric Energy- Harvesting Devices for Generation of Higher Electrical Power Using a Coupled Piezoelectric-Circuit Finite Element Method IEEE Transactions on Ultrasonic’s, Ferroelectrics, and Frequency Control, vol. 57, no. 2, February 2010.

[7] Meiling Zhu, Member, IEEE, Emma Worthington, and Ashutosh Tiwari, Member, IEEE.

 Electrical and Electronics Project by Ravi Devani

MICROCONTROLLER BASED SPEED CONTROL OF THREE PHASE INDUCTION MOTOR USING V/F METHOD

MICROCONTROLLER BASED SPEED CONTROL OF THREE PHASE INDUCTION MOTOR USING V/F METHOD

Electrical and Electronics Project by Ravi Devani

ABSTRACT

Induction motors are widely used AC motors in industrial area. Advanced semiconductor technology & use of microcontroller have made the speed control of induction motor easier. The proposed paper represents variable speed control application of induction motor using v/f method. In this system, the speed of the induction motor can be adjusted to user defined speed. The actual speed & reference speed is compared & the difference is adjusted by changing the firing angles of IGBTs. The system is tested & experimental results are recorded for variable speed under various load conditions.

KEY WORDS- Inverter, rectifier, microcontroller, squirrel cage induction motor.

INTRODUCTION

An industrial drive system basically consists of a mechanical working equipment, or load, which can be kept in motion to turn out mechanical work with the help of prime mover. To transfer energy from prime mover to mechanical load gearing or belt may be used. The transmission may also be required to convert rotary to linear motion and vice versa. Thus a combination of prime mover, transmission equipment, and mechanical working load is called a DRIVE. An electric drive can be defined as a drive, using an electric motor as a prime mover. The electric motors used may require some types of control equipment to achieve speed control and torque control. These controls make the motor work on a specific speed torque curve and may be operated using open loop or closed loop control.

PROPOSED WORK AND ANALYSIS

The present work makes use of DSPIC30F2010 microcontroller, in order to operate induction motor using V/F method. The various factors which make the microcontroller based system attractive are,

1. Improved reliability and increased flexibility.

2. Simplicity of implementation in variable speed drives

3. Low cost and high accuracy

4. Possible to change torque speed characteristics of drive by software modification.

The simplicity of this project is that it can be operate by any person who need not know microcontroller programming.

Block Diagram:

 

Fig. 1 Block diagram of system

Fig.1 shows the block diagram of closed loop control of induction motor using microcontroller DSPIC30F2010. The hardware includes squirrel cage induction motor, rectifier, bridge inverter, microcontroller, speed sensor, and switches for user interface. As shown in the figure single phase A.C. supply is given to the rectifier, rectifier DC output is given to inverter & three phase squirrel cage induction motor is connected to the three phase supply, which is the output of the inverter. Speed of the motor is sensed by sensor and feedback is given to microcontroller, microcontroller generates error signal send it to inverter. Three phase supply generated by the inverter drives the motor at user defined speed.

Electrical and Electronics Project by Ravi Devani

Design specification for each block are given below,

Design Specifications:-

1. Rectifier Block: - A bridge of Diodes

Diode Rating: - 3Amp/1000V

Current passing through diodes = = 0.8 Amp.

Output Voltage of bridge rectifier = 440V A.C. x 1.414 = 622 V D.C

Diode PIV should be greater than 622V (with +/- 10% tolerance)

2. Capacitor Bank:-

Selected Rating :- 470μF/450V 2series, 2parallel

D.C. Current =  = 0.5 Amp.

for 1Amp 1000μF is used by thumb rule

so for 0.5 Amp 500μF is used.

3. IGBT:-

Selected Rating: - 60A/900V

IGBT voltage > 622V

IGBT current > 0.5Amp.

4. Three Phase Squirrel Cage Induction Motor with mechanical load arrangement

0.5 H.P.(375 watt), 3 Phase, 1Amp, 440V, 1440 rpm

IMPLEMENTATION

In this project we have selected uncontrolled bridge rectifier, voltage control inverter, and squirrel cage induction motor, DSpic2010 microcontroller.

Initially user select the speed range from three modes s1=1440 r.p.m. s2=1200 r.p.m, s3=500r.p.m with the help of start key. After selection of the speed range, with increase in the supply voltage motor reaches to reference speed at no-load. With increase in the load gradually the motor speed start to drop, this speed is sensed by speed sensor & converted to voltage in feedback circuit. The actual speed is compared with set speed in controller & if the speed is less than set speed, controller decrease the total time period (T) of PWM so Δt/T increases and the output voltage of PWM i.e. Vout = [(Δt/T) x Vin] increases. In this way the PWM waveform generated by inverter drives the induction motor at set speed by keeping v/f ratio constant.

 

Fig.2 shows total period of the PWM pulse.

 PWM Output Voltage =   

Where,

Δt    = ON time (which is constant)

T     = Total time period

Vin = Supply Voltage

The speed of the motor, terminal voltage of the motor, supply frequency & also v/f ratio has been displayed.

FLOW CHART

Main Circuit:-

Feedback Circuit:-

RESULTS

The complete hardware system has been developed and tested. The motor with ratings of 1440 RPM, 230V, 1Amp, 0.5 H.P. has been tested on no load to full load at user defined speed. The results are tabulated below.

fig. 5.

Fig 6

Electrical and Electronics Project by Ravi Devani

CONCLUSION

When induction motor is connected to the supply directly it runs at rated speed at no load. If the motor is loaded then speed of the motor starts to drop. So to run the motor below rated speed constantly with load and without load v/f method is used. For that to generate PWM waveform and to measure speed of the motor PIC microcontroller is used. The paper represents two algorithms one for measurement of motor speed and other to generate error signal from set speed and actual speed and to adjust the voltage and frequency of the PWM waveform.

From the observation it is concluded that by maintaining constant v/f ratio motor runs at variable speed with load and without load below rated speed. Appendix

Appendixes, if needed, appear before the acknowledgment.

REFERENCES

[1] P.S.Chaudhari, Dr. Pradeep M.Patil, Sharad S. Patil, P.P.Kulkarni, R.M.Holmukhe, “Comparison Of Performance Characteristic of Squirrel Cage Induction Motor by Three Phase Sinusoidal and PWM Inverter Supply using MATLAB Digital Simulation”, Third International Conference on Emerging Trends in Engineering and Technology, 2010 IEEE.

[2] F.A.Ramirez, M.A.Arjona, and C.Hernandez, Mexico, “Space-Vector PWM Voltage-Source Inverter for a Tree-Phase Induction Motor based on the dsPIC30F3011”, Electronics, Robotics and Automation Mechanics Conference, 2009 IEEE.

[3] K.Sandeep Kumar, K.Pritam Satsangi, “Microcontroller Based Closed Loop Control of Induction Motor Using V/f Method”, IET-UK International Conference on Information and Communication Technology in Electrical Sciences (ICTES 2007), Dr. M.G.R.University, Chennai, Tamilnadu, India. Dec. 20-22, 2007.

[4] G.K.Singh, D.K.P.Singh, K.Nam, “A Simple Indirect Field-Oriented Control Scheme for Multiconverter-Fed Induction Motor”, IEEE Transaction on Industrial Electronics, vol.52, No.6, December 2005.

[5] katsunori Taniguchi, member, IEEE, Yasumasa Ogino, and Hisaichi IRIE, “PWM Technique for Power MOSFET Inverter”, IEEE transaction on Power Electronics, vol.3, no.3, July 1988.

[6] S.Flora Viji Rose, Mr. B.V.Manikandan, “Simulation and Implementation of Multilevel Inverter Based Induction Motor Drive”.

[7] Vedam Subrahmanyam, “Electric drives” Tata McGraw-Hill 2005. 

Electrical and Electronics Project by Ravi Devani