final report

A
Project Report
On
“SENSORLESS SPEED PREDICTION OF INDUCTION
MACHINES BY USING FLUCTUATION OF ZERO CROSSING
OF MOTOR CURRENT”
SUBMITTED BY:
Miss. Katkar Priyanka Hanmant
Miss. Nale Supriya Gulabrao
Miss. Junghare Ashwini Bajirao
UNDER THE GUIDANCE OF
Prof. Devi R. J.
DEPARTMENT OF ELECTRONICS ENGINEERING
RAYAT SHIKSHAN SANSTHA’S
KARMVEER BHAURAO PATIL COLLEGE OF
ENGINEERING AND POLYTECHNIC,SATARA.
YEAR 2011-2012
A
Project Report
On
OF MOTOR CURRENT”
SUBMITTED BY:
Prof. Devi R. J.
YEAR 2011-2012
A
Project Report
On
OF MOTOR CURRENT”
SUBMITTED BY:
Prof. Devi R. J.
YEAR 2011-2012

Rayat Shikshan Sanstha’s,
Karmaveer Bhaurao Patil College of Engineering &
Polytechnic, Satara.
Department of Electronics Engineering
Certificate
This is to certify that,
Have completed the project on
“SENSORLESS SPEED PREDICTION OF INDUCTION MACHINES BY
USING FLUCTUATION OF ZERO CROSSING OF MOTOR CURRENT”
during the year 2011-12, to our satisfaction & submitted the project report in the
partial fulfillment of the requirements of grant of term work for the award of
degree of Bachelor of Engineering (Electronics) by Shivaji University,
Kolhapur. Under the curriculum of Bachelor’s degree courses as record of
students own work carried out by them under our supervision & guidance.
Prof. Devi R. J. Prof. Thorat R. A.
Project Guide Head Of Electronic Department

Acknowledgement
“Inspiration and guidance are invaluable aspect for every
student in his life.”
First, we would like to thank Prof. Devi R. J. for his constant
guidance and encouragement throughout the project. His strong
support has helped us a long way towards the successful completion
of project.
It is our pleasure to express sincere thanks to Hon. Principal Prof.
V.B.SABNIS & Head of Electronics Department Prof. R.A.THORAT
for their willful consent, allowing us to take this subject for our
project.
We also want to thank to the other faculty and laboratory staff
of college for helping us to understand the courses and laboratory
work.
Although we have tried to produce the best out of our
Endeavour but their might be some errors, for human beings are not
perfect & “TO ERR IS HUMAN”.
Place: Satara
Date:

INDEX
Sr. no. Chapter Page no.
1. Introduction 1
2. Electronic design and components 4
3. Circuit diagram , description and working 18
4. PCB layout 23
5. Experimental work 26
6. Flowchart 33
7. Programming 38
8. Conclusion 47
9. References 51
10. Papers 53
11. Datasheets 71

“SENSORLESS SPEED DETECTION OF THREE PHASE INDUCTION MOTORS”
K.B.P. COLLEGE OF ENGGINEERING & POLYTECHNIC, SATARA 1
CHAPTER 1
INTRODUCTION

This project is implemented according to the theory proposed from paper “Sensor less
Speed Prediction of Induction Machines by using Fluctuation of zero crossing of Motor Cur-
rent” [refer Papers 1].
Induction motors are widely used in industry and public corporations, etc. Progress in
semi-conductor devices and their applications on induction motors to variable frequency sup-
plies have introduced sophisticated control techniques. These control techniques such as slip
frequency control, flux control, vector control, phase locked loop control, etc, require detec-
tion of rotational speeds of induction motors.
Many works have been done to replace conventional speed transducers in adjustable
drives, by sensing the speed from the electrical quantities applied to the induction motor such
as current and voltage are available for the drive assessment and control.
Recently, sensor less speed control of induction motor drives received great attention
to avoid the different problems associated with direct speed sensor.
1.1 WHY SENSOR LESS?
Nowadays the accuracy and resolution are two critical issues required for speed mea-
surement of induction motor drives. For this purpose an encoder, resolver, tachometers are
used. Due to high installation cost, calibration requirements of frequent maintenance and ad-
ditional cables, sensor less alternatives are become more viable solution. Several works have
been done to detect motor speed without tachometers, encoders, resolvers. However current
methods have already used complex and heavy computation algorithms. Sometimes it is es-
sential to use sensor less speed measurement for explosive environments and for conditions
that unable to connect cable.
In this study, sensor less speed measurement of induction motors using stator current
zero crossings is implemented. It is enough to use current transformer already installed in the
system for remote applications.

1.2 CONCEPT
The aim of this project is to provide with a brief overview of high performance sensor
less induction motor drive. Induction motors have been widely used in high performance AC
drives, requiring information .Introducing shaft speed sensor decreases the system reliability,
and different solutions for sensor less AC drives have been proposed.
The purpose of this project is to implement the sensor less speed detection of induc-
tion machines by using fluctuations of three phase supply current zero crossing only. These
fluctuations are sensed by microcontroller and transferred to pc for speed detection using Fast
Fourier Transformation algorithms. This method is not only suitable to convert it to the on-
line speed prediction using the cascaded digital band pass filters but it may also be possible to
use as a feedback signal. The most important features is being sensor less, and does not re-
quire any additional sensor. Figure 2.1.1 shows block diagram of the ZCT data acquisition
circuit for sensor less speed measurement.
R
Y
B
Fig.2.1.1 Block diagram of the ZCT data acquisition circuit for sensor less speed mea-
surement
3 Phase
Induction
Motor
Buffer1
Buffer2
Buffer3
3
Logic
circuit
ZCT 1
ZCT 2
ZCT 3
µ C
PC
D
B
9

CHAPTER 2
ELECTRONIC DESIGN
& COMPONENTS

2.1 THREE PHASE INDUCTION MOTOR
The three-phase induction motor, also called an asynchronous motor, is the most
commonly used type of motor in industrial applications. In particular, the squirrel-cage de-
sign is the most widely used electric motor in industrial applications.
The electrical section of the three-phase induction motor as shown in Figure 2.1.1
consists of the fixed stator or frame, a three-phase winding supplied from the three-phase
mains and a rotating rotor, bearings and seal(s), and fan. There is no electrical connection be-
tween the stator and the rotor. The currents in the rotor are induced via the air gap from the
stator side. Stator and rotor are made of highly magnetizable core sheet providing low eddy
current and hysteresis losses.
Fig. 2.1.1 Squirrel-cage three-phase induction motor

2.1.1 Stator
The stator winding consists of three individual windings which overlap one another
and are offset by an electrical angle of 120°. The stator is made up of several thin laminations
of aluminum or cast iron. They are punched and clamped together to form a hollow cylinder
(stator core) with slots as shown in Fig.2.1.2. Coils of insulated wires are inserted into these
slots. Each grouping of coils, together with the core it surrounds, forms an electromagnet (a
pair of poles) on the application of AC supply. The number of poles of an AC induction mo-
tor depends on the internal connection of the stator windings. The stator windings are con-
nected directly to the power source. Internally they are connected in such a way, that on ap-
plying AC supply, a rotating magnetic field is created.
Fig. 2.1.2 Stator

2.1.2 Rotor
The rotor is made up of several thin steel laminations with evenly spaced bars, which
are made up of aluminum or copper, along the periphery. In the most popular type of rotor
(squirrel cage rotor), these bars are connected at ends mechanically and electrically by the use
of rings. Almost 90% of induction motors have squirrel cage rotors. This is because the squir-
rel cage rotor has a simple and rugged construction. The rotor consists of a cylindrical lami-
nated core with axially placed parallel slots for carrying the conductors. Each slot carries a
copper, aluminum, or alloy bar. These rotor bars are permanently short-circuited at both ends
by means of the end rings, as shown in Figure 2.1.3. This total assembly resembles the look
of a squirrel cage, which gives the rotor its name. The rotor slots are not exactly parallel to
the shaft.
Fig 2.1.3 Rotor
2.1.3 Operation
The magnetic field generated in the stator induces an EMF in the rotor bars. In turn, a
current is produced in the rotor bars and shorting ring and another magnetic field is induced
in the rotor with an opposite polarity of that in the stator. The magnetic field, revolving in the
stator, will then produces the torque which will “pull” on the field in the rotor and establish
rotor rotation.
As a voltage and a current is applied to the stator winding terminals, a magnetic field
is developed in the windings. The magnetic field appears to synchronously rotate electrically
around the inside of the motor housing.

2.2 CURRENT TRANSFORMER
A current transformer is a type of “Instrument Transformer” that is designed for two
purposes. First, to provide a current in its secondary and it is proportional to the current flow-
ing in its primary. Second, to produce either an alternating current or alternating voltage pro-
portional to the current being measured.
Current Transformers are generally used for measurement and or protective applica-
tions. In measurement Current Transformers one is concerned with the accuracy of the sec-
ondary current over a wide operating range. Protective Current Transformers are specified
by a burden accuracy class and accuracy limit factor.
Current transformers can be of the ring type, bar primary type, or the wound primary
type. In ring and bar primary type current transformer, the primary ampere turns [AT] is fixed
and is equal to, the primary current. The difference between a bar primary and a ring type
current transformer is that in the bar primary version, the bar is fixed integrally with the
CT. for large outputs or for increased accuracy, at low price it may not be possible to manu-
facture ring or bar primary current transformers.
Current transformers are used to sense current overloads, detect ground faults, and
isolate current feedback signals.
The CT uses magnetic fields generated by the AC current flowing through the prima-
ry wire to induce a secondary current. The ratio of the number of secondary turns to the num-
ber of primary turns determines the amplitude of the current on the output. The output of a
CT acts as a current source.
The core on which the secondary wire is wound plays a significant part in the perfor-
mance of a CT. Core types include silicon steel, nickel alloy, or ferrite.
CT cores can be of a solid (closed) or split (open) type. Solid core CTs feature a
closed loop, which the primary conductor must be passed through. Split core CTs can be
temporarily opened to facilitate easier installation. When using a split core CT, the primary
conductor need not be disconnected to install the CT, and in most cases, the conductor can
continue to carry current while the CT is being installed.

2.2.1 Burden
Burden is the maximum load that devices can support while operating within their
accuracy ratings. Typically, burden is expressed in volt-amperes (VA).The burden on a cur-
rent transformer is the ohm value in the secondary circuit, which passes through the current
coil in the meter. The wiring from the CT to the meter is also part of the connected burden.
The thermal burden rating usually coincides with the primary rating factor (RF). Exceeding
this rating will shorten the life of the CT and may cause a loss of accuracy.
2.2.2 Ratio
The ratio of a current transformer refers to the turns ratio of the windings. Like a tra-
ditional voltage transformer, the ratio of the windings determines the relation between the
input and output currents.
2.2.3 Polarity
The CT primary and secondary terminal is physically marked with a polarity. The
marking indicates the instantaneous direction of the secondary current in relation to the pri-
mary current. When current flows in at the marked primary, current is flowing out of the
marked secondary. Figure 2.2.1 shows the symbol of CT
PRI. SEC.
Fig. 2.2.1 Symbol of CT
Hint: Direction of the secondary current can determined as if the two polarity terminals
formed a continuous circuit.

2.3 VOLTAGE FOLLOWER
When the non-inverting amplifier is configured for unity gain, it is called a ‘voltage
follower’ because the output voltage is equal to and in phase with the input. In other words,
in the voltage follower the output follows the input.
The voltage follower is preferred because it has much higher input resistance, and the
output amplitude is exactly equal to the input. Voltage follower is used to provide isolation
between two circuits.
The figure 2.3.1 shows an OP-AMP connected as a VOLTAGE FOLLOWER. Figure 2.3.2
shows waveform of voltage follower.
Fig. 2.3.1 Voltage follower
Fig. 2.3.2 Waveform Of Voltage Follower

2.4 COMPARATOR
A comparator, compares a signal voltage on one input of an op-amp with a known
voltage called reference voltage on the other input. In simplest form, it is nothing more than
an open-loop op-amp, with two analog inputs and a digital output; the output may be (+) or
(-) saturation voltage, depending on which input is the larger.
Comparator is used in circuit such as digital interfacing.
Fig. 2.4.1 Comparator
Fig. 2.4.2 Waveform of Voltage Comparator

2.5 MICROCONTROLLER
2.5.1 The core features of AT89C2051
• Compatible with MCS®-51Products
• 2K Bytes of Reprogrammable Flash Memory Endurance: 10,000 Write/Erase Cycles
• 2.7V to 6V Operating Range
• Fully Static Operation: 0 Hz to 24 MHz
• Two-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 15 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial UART Channel
• Direct LED Drive Outputs
• On-chip Analog Comparator
• Low-power Idle and Power-down Modes
• Green (Pb/Halide-free) Packaging Option
The pin outs of the AT89C2051 is given in figure2.5.1
Fig 2.5.1 pin outs of the AT89C2051
2.5 MICROCONTROLLER
2.5 MICROCONTROLLER

2.6 SERIAL COMMUNICATION
Serial communication is a way enables different equipments to communicate with
their outside world. It is called serial because the data bits will be sent in a serial way over a
single line. A personal computer has a serial port known as communication port or COM Port
used to connect a modem or any other device, there could be more than one COM Port in a
PC.
Serial ports are controlled by a special chip called UART (Universal Asynchronous
Receiver Transmitter). Different applications use different pins on the serial port and this bas-
ically depend of the functions required.
Fig 2.6.1 serial communication
2.6.1 Communication methods
There are two methods for serial communication, Synchronous & Asynchronous.

2.6.1.1 Synchronous communication
In Synchronous serial communication the receiver must know when to “read” the next
bit coming from the sender, this can be achieved by sharing a clock between sender and re-
ceiver.
In most forms of serial Synchronous communication, if there is no data available at a
given time to transmit, a fill character will be sent instead so that data is always being trans-
mitted. Synchronous communication is usually more efficient because only data bits are
transmitted between sender and receiver; however it will be more costly because extra wiring
and control circuits are required to share a clock signal between the sender and receiver.
2.6.1.2 Asynchronous communication
Asynchronous transmission allows data to be transmitted without the sender having to
send a clock signal to the receiver. Instead, special bits will be added to each word in order to
synchronize the sending and receiving of the data.
When a word is given to the UART for Asynchronous transmissions, a bit called the
"Start Bit" is added to the beginning of each word that is to be transmitted. The Start Bit is
used to alert the receiver that a word of data is about to be sent, and to force the clock in the
receiver into synchronization with the clock in the transmitter. Figure 2.6.2 shows Example
of serial data transmission.
Fig 2.6.2 Example of serial data transmission
After the Start Bit, the individual bits of the word of data are sent, each bit in the word
is transmitted for exactly the same amount of time as all of the other bits.
When the entire data word has been sent, the transmitter may add a Parity Bit that the
transmitter generates. The Parity Bit may be used by the receiver to perform simple error
checking. Then at least one Stop Bit is sent by the transmitter.
If the Stop Bit does not appear when it is supposed to, the UART considers the entire
word to be garbled and will report a Framing Error.
The standard serial communications hardware in the PC does not support Synchron-
ous operations.

2.6.3 RS232
RS-232 (Recommended standard-232) is a standard interface approved by the Elec-
tronic
Industries Association (EIA) for connecting serial devices.
2.6.4 RS232 on DB9 (9-pin D-type connector)
There is a standardized pin out for RS-232 on a DB9 connector, as shown below
Fig 2.6.3 DB9 connector

Pin Signal Signal Name Typical purpose
1 DCD Data carrier detect
DCE is connected to the telephone line.
2 RxD Receive Data
Carries data from DCE to DTE.
3 TxD Transmit Data
Carries data from DTE to DCE.
4 DTR Data terminal ready
Indicates presence of DTE to DCE.
5 GND Signal ground
Ground
6 DSR Data set ready
Carries data from DTE to DCE.
7 RTS Request to send
DTE requests the DCE prepare to receive data.
8 CTS Clear to send
Indicates DCE is ready to accept data.
9 RI Ring Indicator DCE has detected an incoming ring signal on
the telephone line.
Table 2.6.1 Pin Description

2.7 DB9 CONNECTOR
The term "DB9" refers to a common connector type, one of the D-Subminiature or D-
Sub types of connectors. DB9 has the smallest "footprint" of the D-Subminiature connectors,
and houses 9 pins (for the male connector) or 9 holes (for the female connector).
A db9 connector is a type of connector that has to be used to integrate a device or
hardware with another one or with a computer. Normally these connectors are used in com-
puters and that is why we are going to give examples of those devices that are related to com-
puters. A db9 connector will have 9 connecting points in total that will help you to attach or
plug another connector in them. If you have a male connector then you will need a female
connector to attach your device and if you have a female connector then you will need a
make connector to attach your device properly. Male and Female D-Type connectors are
shown in figure bellow.
(a).9 Pin Male D-Type plug Connector (b).9 Pin Female D-Type plug Con-
nector
Fig 2.15 Types of connector

CHAPTER 3
CIRCUIT DIGRAM,DESCRIPTION
AND WORKING

U1A
LM324AJ
3
2
11
4
1 U1B
LM324AJ
5
6
11
4
7
U1C
LM324AJ
10
9
11
4
8
U1D
LM324AJ
12
13
11
4
14
U2A
LM324AJ
3
2
11
4
1
U2B
LM324AJ
5
6
11
4
7
R1
27 Ohm
R2
27 Ohm
R3
27 Ohm
R4
27 Ohm
R5
27 Ohm
R6
27 Ohm
R7
100 Ohm
R8
100 Ohm
R9
100 Ohm
R10
22kOhm
R11
22kOhm
R12
22kOhm
C1
47nF
C2
47nF
C3
47nF
7404N
7432N
7432N
7432N
7408N
7408N
7408N
I1
10mA
50 Hz
0Deg
I2
10mA
50 Hz
0Deg
I3
10mA
50 Hz
0Deg
AT89C2051
1uF-POL
INT0
INT1
XTAL1
XTAL2
GND
T0
T1
TXD
RXD
RST/VPP
VCC
R1
8.2kOhm
22pF
22pF
U2A
7404N*
2
1
4
3
5
6
7
8
9
10
20
1kOhm
1kOhm
1kOhm
1kOhm
1kOhm
1kOhm
1kOhm
1kOhm
LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8
C4
0.1uF
1uF-POL 1uF-POL
1uF-POL
1uF-POL
1uF-POL
DB9
1
2
3
4
5
6
7
8
16
15
14
13
12
11
max232
12MHZ
T1
IRON_CORE_XFORMER*
6-0V,500mA
D1
1B4B42*
1
2
4
3
V1
230 V
50 Hz
0Deg
U1
LM7805CT*
LINE VREG
COMMON
VOLTAGE
C1
1000uF
C2
0.01uF
R1
1kOhm
LED1
U2
NET_8
TC7660
C3
10uF
C4
10uF

3.1 ZERO CROSSING DETECTORS
A zero crossing detector is a comparator with the reference level set at zero. It is used
for detecting the zero crossings of AC signals. It can be made from an operational amplifier
with an input voltage at its positive input (refer circuit diagram figure 3.1.1).
When the input voltage is positive, the output voltage is a positive value, when the in-
put voltage is negative, the output voltage is a negative value. The magnitude of the output
voltage is a property of the operational amplifier and its power supply.
Fig 3.1.1 Zero Crossing Detectors
Fig 3.1.2 Input Output Waveforms

3.2 REGULATED DC POWER SUPPLY:-
Fig 3.2.1 Regulated DC power supply
3.2.1 Positive Voltage Regulator(IC 7805)
 Output Current up to 1A
 Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V
 Thermal Overload Protection
 Short Circuit Protection
 Output Transistor Safe Operating Area Protection
3.2.2 Positive To Negative Dc Voltage Converter (TC7660)
 Wide Input Voltage Range: +1.5V to +10V
 Efficient Voltage Conversion (99.9%, typ.)
 Excellent Power Efficiency (98%, typ.)
 Low Power Consumption: 80 μA (typ.)
 Low Cost and Easy to Use Only Two External Capacitors Required
 Available in 8-Pin Small Outline (SOIC), 8-Pin PDIP and 8-Pin CERDIP Packages
 Improved ESD Protection (3 kV HBM)
 No External Diode Required for High-Voltage Operation

3.3 WORKING
When three phase induction motor starts the fluctuations of the three phase supply
current can be taken with the help of ring type current transformer. The decreased values of
stator current using three ring type current transformers for each phase is converted to one
square wave by logic gates. This square wave has pulse width is equal to 3333µs. The motor
current zero crossing detection circuit includes the voltage follower, voltage comparator and
Schmitt trigger connected in series. Negative feedback is given to voltage follower. The out-
put voltage of voltage follower is same as the input voltage. Therefore the voltage gain of
voltage follower is unity. Sampling of the signal is done by using logic gates.
Voltage comparator compares reference signal with the ground signal. The output vol-
tage of voltage comparator is input to logic circuitry. Output of inverter gate is given to INT0
and INT1 inputs of the microcontroller. Two 16 bit timers in 8-bit microcontroller is used to
calculate time difference of each adjacent zero crossings. Each timer is interrupted on either
positive rising edge or negative falling edge of ZCT signal. External interrupt 0 is enabled at
the negative falling edge of the ZCT signal at that instance counter starts counting. Counter
counts up to next triggering will occur. As the next triggering occurred counter stops the
counting. Microcontroller saves the counted pulse width into the memory location of micro-
controller. As the next triggering will occur then another external interrupt is enabled. It
counts pulse width and save to next memory location and the same process is continued.
The ZCT data obtained is serially transmitted to PC through serial communication.
The asynchronous transmission method is used for serial transmission by adding start and
stop bits. The transmitted data is collected at 9600 baud rate using HyperTerminal by select-
ing com1 port. This data is captured for 20 second in text file. For signal processing import
this data into MATLAB software. After importing data into MATLAB convert this data from
cell to matrix using function cell2mat() then convert data into double data type. This con-
verted data is input for plotting the frequency spectrum. Frequency Spectrum is plotted using
Welch method. Speed related frequency component can be observed from plotted figure at 23
to 25 HZ frequency band. Spectral peak is observed within this frequency band amplitude of
that spectral peak is nothing but the speed of induction motor.

CHAPTER 4
PCB LAYOUT

4.1 TOP LAYER
4.1 TOP LAYER
4.1 TOP LAYER

4.2 BOTTOM LAYER
4.2 BOTTOM LAYER
4.2 BOTTOM LAYER

CHAPTER 5
EXPERIMENTAL
WORK

5.1 TESTING OF HARDWARE
5.1.1 Function generator used as input voltage source
Vin = 3V
a. OPAMP LM324
Pin No 3 Amplitude=1.2V (Input)
Pin No 1 Amplitude=1.2V (Output)
Pin No 4 Amplitude=+5V (DC Voltage)
Pin No 5 Amplitude=1.2V (DC Voltage)
Pin No 6 Amplitude=0V (Ground)
Pin No 7 Amplitude=8.4V
Pin No 11 Amplitude=-1.2V (DC Voltage)
Pin No 13 Amplitude=0 (Ground)
b. AND GATE (7408)
Pin No 14 Amplitude=5V (DC Voltage)

c. OR GATE (7432)
Pin No 14 Amplitude=5V (DC Voltage)
d. NOT GATE (7404)
Pin No 2 Amplitude=8.4V (Output) i.e. inverted output
5.1.2 Current Transformer Used As Input
Three phase supply voltage=394V
a. OPAMP LM324
Pin No 7 Amplitude=5V
b. MICROCONTROLLER (89C2051)
c. MAX232
d. DB9

5.2 CURRENT TRANSFORMER
NOTE
The current transformer enters into saturation region then also it is used only for the purpose
of obtaining zero crossing detection.
Sr
No
Primary Vol-
tage
Primary
Current (A)
Voltmeter
Reading
(mV)
Secondary Current
(mA)
Load
(W)
1 230 5 26 0.3 500
2 230 6.5 15.7 0.4 1000
3 230 8 18.3 0.41 1500
4 230 9.5 15.4 0.42 2000
5 230 11 10.3 0.45 2500

5.3 PHOTOGRAPHS
Fig 5.3.1 Three Phase Squirrel Cage Induction Motor
Specifications:
Volts 415V
K.W. 2.2V
Speed 1430RPM
Current 5 star
H.P. 3

Fig 5.3.2 Experimental Set Up
Fig 5.3.3 output at pin no 3 of microcontroller (refer circuit diagram)

Fig 5.3.3 output at pin no11 of Max232 (refer circuit diagram)

CHAPTER 6
FLOWCHARTS

6.1 IMPLEMENTATION
START
Obtaining the stator current signal
ON line speed prediction
Obtaining zero crossing fluctuations from motor current
signal
OFF line speed prediction
ZCT signal is passed to microcontroller by enabling external interrupts
store the counted pulse width into memory locations of microcontroller
Serial transmission from microcontroller to PC
Save the received data into text file
Import the data into MATLAB software
Plot the frequency spectrum and detect the speed
from this frequency spectrum
Convert the data into double format
STOP

6.2 MICROCONTROLLER PROGRAMMING
START
Initialize global variable
Initialize Timer0 in MODE1(16 bit)
Initialize Timer1 in Auto Reload Mode. Load
Count in TH1 and TL1 for serial communication.
Initialize SCON for serial communication
mode1.Initialize IE to make all interrupt enable.
Run Timer0 and Timer1.
Wait for interrupt.
Whether interrupt
Is of serial
interrupt?
Go to ISR of external interrupt 0. Go to ISR of serial communication.
Initialize local variable.
Stop timer0
Initialize local variable.
If transmission is completed then
make TI bit 0.
B
b
b
B
B
B
B
A
C
ED

Take timer count from TH0 and
TL0.Concatenate TH0 and TL0.
Take byte from string1 convert
that byte into ASCII form.
B C
Store TH0 and TL0 count in string
(say string 1).
Increase string1 position by 1.
Make TH0 and TL0 count as 00H. Increase string2 position by 1.
Take byte from string2 for
transmission.
Store ASCII values in another
string (say string2).
Run timer TR0.
D
E

6.3 MATLAB PROGRAMMING
Import the data from text file into MATLAB workspace
Conversion from cell to matrix
Plot the frequency spectrum using pwelch () function
START
STOP

CHAPTER 7
PROGRAMMING

7.1 MICROCONTROLLER PROGRAM
7.1.1 CONFIGURATION
1. TMOD:
MSB TIMER1 TIMER0 LSB
GATE C/T M1 M0 GATE C/T M1 M0
0 0 1 0 0 0 0 1
2 1
21H
2. TCON:
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
0 0 0 1 0 0 0 0
1 0
10H
3. SCON:
SM0 SM1 SM2 REN TB8 RB8 TI RI
0 1 0 0 0 0 0 0
4 0
40H

4. Defining TH1
Baud rate = 9600
=
SMOD=0
= ×
⁄
( − )
= ×
× ⁄
( − )
TH1= FD H
5. IE
EA - ET2 ES ET1 EX1 ET0 EX0
1 0 0 1 0 0 0
1
9 1
91H
6. IP:
- - PT2 PS PT1 PX1 PT0 PX0
0 0 0 0 0 0 0 1
0 1
01H

7.1.2 PROGRAM
#include<C:KeilC51INCAtmelAT892051.h>
unsigned char str[30];
unsigned char str1[60];
char a=0,b=0,g=0,h=0;
/*SUBROUTINE FOR EXTERNAL INTERRUPT*/
void intr0() interrupt 0 // external interrupt0 ISR
{
unsigned int p,q,r,s,t;
unsigned int d=0x94; // fixed count
TR0=0; // stop TIMER0
p = TH0 << 8; // make lower byte as higher byte of TH0
q = TL0; // load TL0 to temporary variable
r = q + p; // concatenation of TH0 and TL0
s = r + d; // add fixed count into TH0 & TL0
t = s;
s = s & 0xff00; // mask lower byte of count
s = s >> 8;
if(a==30)
{
a=0;
}
str[a] = s; // load higher byte of count
a++; // increment string
str[a] = t; // load lower byte of count into string
a++; // increment string
TH0 = 0x00; // reset TH0
TL0 = 0x00; // reset TL0
TR0 = 1; // run the TIMER0
}

/*SUBROUTINE FOR SERIAL INTERRUPT*/
void serial() interrupt 4 // serial interrupt ISR
{
unsigned int j,k,l,m,n;
if(TI == 1) // check TI flag of SCON
{
TI = 0; // make TI=0
if(b==60)
{
b=0;
}
}
j = str[b] // take data for ASCII code conversion
/*CODE FOR HEX TO ASCII CONVERSION */
m = j & 0xf0; // mask lower nibble of count
m = m >> 4;
if(h==60)
{
h=0;
}
if(m ==0 || m <= 9)
{
m = m + 0x30; // hex for ASCII character in between 0 & 9
str1[h] = m; // store the ASCII values into string
}
else
{
n = m + 6; // make BCD number
n = n + 0x31; // hex for ASCII character other than in between 0 & 9
str1[h] = n; // store the ASCII values into string
}
h++;
k = j & 0x0f; // mask higher nibble of count
if(k == 0 || k <= 9) // check the masked nibble whether it is in between 0
//&9
{
k = k + 0x30; // hex for ASCII character in between 0 & 9
str1[h] = k; // store the ASCII values into string
}

else
{
l = k + 6; // make BCD number
l = l + 0x31; // hex for ASCII character other than in between 0 & 9
str1[h] = l; // store the ASCII values into string
}
h++; // increment the string
b++; // increment the string
TR1 = 1; // run TIMER1
if(g==60)
{
g=0;
}
SBUF = str1[g]; // load the contents of str1 into SBUF
g++; // increment the string
}
}
void main()
{
TCON = 0x10 ;
TMOD = 0x21; /* TIMER0 in mode1 (16-bit TIMER mode) and
TIMER1 IN mode2 (8-bit auto reload)*/
TH1 = 0xFD; // load higher byte for the selection of baud rate
TL1 = 0xFD; // load lower byte for the selection of baud rate
IT0 = 1; /* enable bit IT0 in IE0 register for making edge trig-
gered
Interrupt*/
SCON = 0x40; // enable serial mode2 of SCON register
IE = 0x91; // enable EA, ES, EX0 of IE register
IP = 0x01; // select priority first to EXTERNAL INTERRUPT0
SBUF= 's'; // start transmission
while(1){} // wait for interrupt(either serial or external interrupt)
}

7.2 MATLAB PROGRAMMING
7.2.1 FUNCTIONS
7.2.1.1 pwelch
PSD using Welch's method
Syntax
[Pxx,w] = pwelch(x)
[Pxx,f] = pwelch(x,window,noverlap,nfft,fs)
Description
[Pxx,w] = pwelch(x) estimates the power spectral density Pxx of the input signal vec-
tor x using Welch's averaged modified periodogram method of spectral estimation.
 The vector x is segmented into eight sections of equal length, each with 50% overlap.
 Any remaining (trailing) entries in x that cannot be included in the eight segments of
equal length are discarded.
 Each segment is windowed with a Hamming window that is the same length as the
segment.
[Pxx,f] = pwelch(x,window,noverlap,nfft,fs) uses the sampling frequency fs specified
in hertz (Hz) to compute the PSD vector (Pxx) and the corresponding vector of fre-
quencies (f). In this case, the units for the frequency vector are in Hz. The spectral
density produced is calculated in units of power per Hz. If you specify fs as the emp-
ty vector [], the sampling frequency defaults to 1 Hz.

7.2.1.2 cell2mat
Convert cell array of matrices to single matrix
Syntax
m = cell2mat(c)
Description
m = cell2mat(c) converts a multidimensional cell array c with contents of the same
data type into a single matrix, m. The contents of c must be able to concatenate into a
hyper rectangle. Moreover, for each pair of neighboring cells, the dimensions of the
cells' contents must match, excluding the dimension in which the cells are neighbors.
7.2.1.3 double
Convert to double precision
Syntax
double (x)
Description
double (x) returns the double-precision value for X. If X is already a double-precision
array, double has no effect.

7.2.2 PROGRAM
clc;
clear all;
Fs=300; %sampling frequency
uiimport; %import data
p=cell2mat(u); % convert cell to matrix
s=double(p); % convert data in to double
pwelch(s,1024,120,[],95,'twosided'); % plot the frequency spectrum using pwelch
% method
Results
Note:
Frequency band from 23Hz to 25Hz contains the modulating frequency components
therefore the frequency related speed component is selected from this frequency band,
where large spectral peak is observed.
0 10 20 30 40 50 60 70 80 90
-30
-20
-10
0
10
20
30
40
50
Frequency (Hz)
Power/frequency(dB/Hz)
Welch Power Spectral Density Estimate
X: 23.75
Y: 18.23
data1
fr

CHAPTER 8
CONCLUSION

8.1 CAPTURE THE DATA THROUGH HYPERTERMINAL
Fig 8.1.1 data captured for 5 seconds

Fig 8.1.2 data captured for 10 seconds

8.2 OBSERVED RESULTS
Sr. No. Supply
Voltage(V)
Tachometer
Reading
(rpm)
Rotor Freq.
From Soft-
ware ( Hz)
Computed
Speed In
(Rpm)
Error In %
1. 334 1470 24.3 1462 0.5
2. 360 1481 24.5 1475 0.4
3. 381 1487 24.7 1482 0.3
4. 390 1490 24.88 1493 0.3
5. 394 1494 24.9 1494 0
From these experimental results we conclude that, sensor less speed determination by
ZCT method has high speed accuracy with no need any compensation. ZCT method is
not influenced by unbalanced supply.

CHAPTER 9
REFERENCES

Books
1. ‘Principles of electrical engineering’ -B. L. Thareja (vol-II)
2. ‘MATLAB PROGRAMMING’ –STEPHAN .J. Chapman
3. A. Gayakwad R.”Op amps And Linear Integrated Circuits”, 2nd
Edition, Prentice Hall.
Other references
1. Hakan Calic, Ahmet Turan Ozcerit, Ibrahim Cetiner, Osman Gurdal,
Abdulkadir Cakir , ”Sensor less Speed Prediction of Induction Machines by using
Fluctuation of zero crossing of Motor Current”.
2. Osman Gurdal , Orhan Secur “New sensor less speed detection method in induction
motor”.
3. Wang.Y.”The ZCT method of induction motor failure prediction and speed monitor-
ing”, pdf thesis.
Websites
1. www.alldatasheets.com
2. www.seminorproject.com
3. www.8051projects.com

CHAPTER 10
PAPERS

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