Ac Motor Doc

Chapter 1

INTRODUCTION 1.1 Embedded Systems

Embedded system is a combination of hardware and software, it is also named

as “Firm ware”. An embedded system is a special purpose computer system, which is

completely encapsulated by the device it controls. It is a computer-controlled system

An embedded system is a specialized system that is a part of a larger system

or machine. As a part of a larger system it largely determines its functionality.

Embedded systems are electronic devices that incorporate microprocessors with in

their implementations.

Embedded systems provide several major functions including monitoring of

the analog environment by reading data from sensors and controlling actuators.

Inputs (sensor) Outputs (actuator)

Figure1.1: a real time system interacts with environment

Embedded systems are designed to do some specific task rather than be a

general-purpose computer for multiple tasks. Some also has real time performance

constraints that must be met, for reason such as safety and usability; others may have

low or no performance requirements, allowing the system hardware to be simplified

to reduce costs.

An embedded system is not always a separate block - very often it is

physically built-in to the device it is controlling.

The software written for embedded systems is often called firmware, and is

stored in read-only memory or flash convector chips rather than a disk drive. It often

runs with limited computer hardware resources: small or no keyboard, screen, and

little memory.

1

EmbeddedSystem

1.2 Block Diagram

1.3 Block Diagram DescriptionIn this section we will be discussing about complete block diagram and its

functional description of our project. And also brief description about each block

of the block diagram.

Power supply

Microcontroller

DTMF

TRIACS

Devices

1.3.1 Power Supply

2

AT89S52

Micro

controller unitDTMF

HT9170B

POWERSUPPLY

(GSM)MOBIL

E

BT136TRIAC

DRIVER

AC MOTORMOBILE

CONNECTOR

In this system we are using 5V power supply for microcontroller of

Transmitter section as well as receiver section. We use rectifiers for converting the

A.C. into D.C and a step down transformer to step down the voltage. The full

description of the Power supply section is given in this documentation in the

following sections i.e. hardware components.

1.3.2 Microcontroller

In this project the micro-controller is playing a major role. Micro-

controllers were originally used as components in complicated process-control

systems. However, because of their small size and low price, Micro-controllers are

now also being used in regulators for individual control loops. In several areas

Micro-controllers are now outperforming their analog counterparts and are cheaper as

well.

The purpose of this project work is to present control theory that is

relevant to the analysis and design of Micro-controller system with an emphasis on

basic concept and ideas. It is assumed that a Microcontroller with reasonable

software is available for computations and simulations so that many tedious details

can be left to the Microcontroller. The control system design is also carried out up to

the stage of implementation in the form of controller programs in assembly language

OR in C-Language.

1.3.3 DTMF (Dual Tone Multi Frequency)

A DTMF is used to decode the frequency and to give the instructions

to microcontroller.

1.3.4 TRIAC

A TRIAC, or TRIode for Alternating Current is an electronic component

approximately equivalent to two silicon-controlled rectifiers (SCRs/thyristors) joined

in inverse parallel (paralleled but with the polarity reversed) and with their gates

connected together. The formal name for a TRIAC is bidirectional triode thyristor.

1.3.5 Devices

Here devices or Appliances are interfaced with the micro controller .based on

the input instruction the particular appliance is operated.

3

1.4 Schematic

1.4.1 Schematic ExplanationThe main aim of this power supply is to convert the 230V AC into 5V DC in

order to give supply for the TTL. This schematic explanation includes the detailed pin

connections of every device with the microcontroller.

This schematic explanation includes the detailed pin connections of every

device with the microcontroller. The pin no 23 and 25 are grounded in such a way

that voice record and play back will be possible. The mobile will be connected to the

speaker pins.

Let us see the pin connections of each and every device with the

microcontroller in detail.

Chapter 2

4

MICRO CONTROLLER (AT89S52)2.1 Introduction

A Micro controller consists of a powerful CPU tightly coupled with memory,

various I/O interfaces such as serial port, parallel port timer or counter, interrupt

controller, data acquisition interfaces-Analog to Digital converter, Digital to Analog

converter, integrated on to a single silicon chip.

One of the major differences between a Microprocessor and a Micro

controller is that a controller often deals with bits not bytes as in the real world

application. Intel has introduced a family of Micro controllers called the MCS-51.

2.2 Features

Compatible with MCS-51 Products

8 Kbytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Fully Static Operation: 0 Hz to 24 MHz

Three-Level Program Memory Lock

256 x 8-Bit Internal RAM

32 Programmable I/O Lines

Three 16-Bit Timer/Counters

Eight vector two level Interrupt Sources

Programmable Serial Channel

Low Power Idle and Power Down Modes

2.3 DescriptionThe AT89S52 provides the following standard features: 8Kbytes of Flash, 256

bytes of RAM, 32 I/O lines, three 16-bit timer/counters, six-vector two-level interrupt

architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In

addition, the AT89S52 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The Idle Mode

stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt

system to continue functioning. The Power down Mode saves the RAM contents but

freezes the oscillator, disabling all other chip functions until the next hardware reset.

5

2.4 Block Diagram

Figure2.1: Block diagram of AT89S52

2.5 Pin Diagram

6

Figure2.2 pin diagram

2.6 Pin Description• VCC - Supply voltage.

• GND - Ground.

2.6.1 Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each

pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be

used as high-impedance inputs. Port 0 can also be configured to be the multiplexed

low-order address/data bus during accesses to external program and data memory. In

this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash

programming and outputs the code bytes during program verification. External pull-

ups are required during program verification.

2.6.2 Port 1

7

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1

output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins,

they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port

1 pins that are externally being pulled low will source current (IIL) because of the

internal pull-ups. Port 1 also receives the low-order address bytes during Flash

programming and verification.

2.6.3 Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2

output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins,

they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port

2 pins that are externally being pulled low will source current (IIL) because of the

internal pull-ups. Port 2 also receives the high-order address bits and some control

signals during Flash programming and verification.

2.6.4 Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3

output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins,

they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port

3 pins that are externally being pulled low will source current (IIL) because of the

pull-ups. Port 3 receives some control signals for Flash programming and

verification. Port 3 also serves the functions of various special features of the

AT89S52, as shown in the following table.

8

2.6.5 RST

Reset input. A high on this pin for two machine cycles while the oscillator is

running resets the device. This pin drives High for 98 oscillator periods after the

Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to

disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature

is enabled.

2.6.6 ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of

the address during accesses to external memory. This pin is also the program pulse

input (PROG) during Flash programming. In normal operation, ALE is emitted at a

constant rate of 1/6 the oscillator frequency and may be used for external timing or

clocking purposes. Note, however, that one ALE pulse is skipped during each access

to external data memory. If desired, ALE operation can be disabled by setting bit 0 of

SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC

instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has

no effect if the microcontroller is in external execution mode.

2.6.7 PSEN

Program Store Enable (PSEN) is the read strobe to external program memory.

When the AT89S51 is executing code from external program memory, PSEN is

activated twice each machine cycle, except that two PSEN activations are skipped

during each access to external data memory.

9

2.6.8 EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the

device to fetch code from external program memory locations starting at 0000H up to

FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally

latched on reset. EA should be strapped to VCC for internal program executions. This

pin also receives the 12-volt programming enable voltage (VPP) during Flash

programming.

2.6.9 XTAL1

Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

2.6.10 XTAL2

Output from the inverting oscillator amplifier.

2.7 Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively, of an inverting

amplifier which can be configured for use as an on-chip oscillator, as shown in Figs

2.5.1. Either a quartz crystal or ceramic resonator may be used. To drive the device

from an external clock source, XTAL2 should be left unconnected while XTAL1 is

driven as shown in Figure 2.5.2.There are no requirements on the duty cycle of the

external clock signal, since the input to the internal clocking circuitry is through a

divide-by-two flip-flop, but minimum and maximum voltage high and low time

specifications must be observed.

Fig2.3: Oscillator Connections Fig2.4: External Clock Drive Configuration

10

Chapter 3

DTMF (DUAL TONE MULTI FREQUENCY)3.1 Introduction

The M-8870 is a full DTMF Receiver that integrates both band split filter and

decoder functions into a single 18-pin DIP or SOIC package. Manufactured using

CMOS process technology, the M-8870 offers low power consumption (35 mW max)

and precise data handling. Its filter section uses switched capacitor technology for

both the high and low group filters and for dial tone rejection. Its decoder uses digital

counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code.

External component count is minimized by provision of an on-chip differential input

amplifier, clock generator, and latched tri-state interface bus. Minimal external

components required include a low-cost 3.579545 MHz color burst crystal, a timing

resistor, and a timing capacitor.

The M-8870 provides a “power-down” option which, when enabled, drops

consumption to less than 0.5 mW. The M-8870-02 can also inhibit the decoding of

fourth column digits

3.1.1 Featureso Low Power Consumption

o Adjustable Acquisition and Release Times

o Central Office Quality and Performance

o Power-down and Inhibit Modes (-02 only)

o Inexpensive 3.58 MHz Time Base

o Single 5 Volt Power Supply

o Dial Tone Suppression

11

3.2 Block Diagram

Fig3.1: Block Diagram of M-8870-01

3.3 Pin Diagram

12

3.3.1 Pin Description

3.4 Functional DescriptionThe HT9170B/D tone decoders consist of three band pass filters and two

digital decode circuits to convert a tone (DTMF) signal into digital code output. An

operational amplifier is built-in to adjust the input signal. The pre-filter is a band

rejection filter, which reduces the dialing tone from 350Hz to 400Hz. The low group

filter filters low group frequency signal output whereas the high group filter filters

high group Frequency signal output. A zero-crossing detector with follows each

filters output hysteretic. When each signal amplitude at the output exceeds the

specified level, it is transferred to full swing logic signal. When input signals are

recognized to be effective, DV becomes high, and the correct tone code (DTMF) digit

is transferred.

3.4.1 Steering control circuit

The steering control circuit is used for measuring the effective signal duration

and for protecting against drop out of valid signals. It employs the analog delay by

13

external RC time-constant controlled by EST. The EST pin is normally low and

draws the RT/GT pin to keep low through discharge of external RC. When a valid

tone input is detected, EST goes high to charge RT/GT through RC. When the

voltage of RT/GT changes from 0 to VTRT (2.35V for 5V supply), the input signal is

effective, and the code detector will create the correct code. After D0~D3 are

completely latched, DV output becomes high. When the voltage of RT/GT falls down

from VDD to VTRT (i.e. when there is no input tone), DV output becomes Low, and

D0~D3 keeps data until a next valid tone input is produced. By selecting adequate

external RC value, the minimum acceptable input tone duration (tACC) and the

minimum acceptable inter-tone rejection (tIR) can be set. External Components (R,

C) are chosen by the formula.

tACC=tDP+tGTP;

tIR=tDA+tGTA;

Where tACC: Tone duration acceptable time

TDP: EST output delay time (_L__H_)

TGTP: Tone present time

TIR: Inter-digit pause rejection time

TDA: EST output delay time (_H__L_)

tGTA: Tone absent time

14

3.4.2 Timing Diagram

3.4.3 Pin Diagram Of CM8870

15

3.5 Applications

PABX

Central office

Mobile radio

Remote control

Remote data entry

Call limiting

Telephone answering systems

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Chapter 4

Pulse Width Modulation (PWM)4.1 Introduction

PWM is a way of digitally encoding analog signal levels. Through the use of

high-resolution counters, the duty cycle of a square wave is modulated to encode a

specific analog signal level. The PWM signal is still digital because, at any given

instant of time, the full AC supply is either fully on or fully off. The voltage or

current source is supplied to the analog load by means of a repeating series of and off

pulse.

The on time is the time during which the AC supply is applied to the load and

the off time is the periods during which that supply is switched off. Given a sufficient

bandwidth, any analog value can be encoded with PWM.

Many micro controllers include PWM controllers. For example, Microchip’s

PIC16C67 includes two, each of which has a selectable on-time and period. The duty

cycle is the ratio of the on-time to the period.

4.2 Advantages of PWMPWM is economical, space saving. The signal remains digital all the way

from the processor to the controlled system. No digital-to –analog conversion is

necessary. By keeping the signal digital, noise immunity is yet another benefit of

choosing PWM over analog control and is the principal reason PWM is sometimes

used for communication.

4.3 Applications of PWM:PWM is employed in a wide variety of applications, ranging from

Measurement and communication to power control and conversion. As a concrete

example consider a PWM-controlled brake. To put it simply, a brake is a device that

clamps down hard on something in many brakes; the amount of clamping pressure is

controlled with an analog input signal. The more voltage or current that’s applied to

the brake, the more pressure the brake will exert. The output of a PWM controller

could be connected to a switch between the supply and the brake to produce more

stopping power, the software need only increase the duty cycle of the PWM output.

17

Chapter 5

REGULATED POWER SUPPLY5.1 Introduction

There are many types of power supply. Most are designed to convert high

voltage AC mains electricity to a suitable low voltage supply for electronic circuits

and other devices. A power supply can by broken down into a series of blocks, each

of which performs a particular function.

For example a 5V regulated supply can be shown as below

Fig 5.1: Block Diagram of a Regulated Power Supply System

Similarly, 12v regulated supply can also be produced by suitable selection of

the individual elements. Each of the blocks is described in detail below and the power

supplies made from these blocks are described below with a circuit diagram and a

graph of their output:

5.2 TransformerA transformer steps down high voltage AC mains to low voltage AC. Here we

are using a center-tap transformer whose output will be sinusoidal with 36volts peak

to peak value.

Fig5.2: Output Waveform of transformer

18

The low voltage AC output is suitable for lamps, heaters and special AC

motors. It is not suitable for electronic circuits unless they include a rectifier and a

smoothing capacitor. The transformer output is given to the rectifier circuit.

5.3 RectifierA rectifier converts AC to DC, but the DC output is varying. There are several

types of rectifiers; here we use a bridge rectifier.

The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage

using both half cycles of the input ac voltage. The Bridge rectifier circuit is shown in

the figure. The circuit has four diodes connected to form a bridge. The ac input

voltage is applied to the diagonally opposite ends of the bridge. The load resistance is

connected between the other two ends of the bridge.

For the positive half cycle of the input ac voltage, diodes D1 and D3 conduct,

whereas diodes D2 and D4 remain in the OFF state. The conducting diodes will be in

series with the load resistance RL and hence the load current flows through RL.

For the negative half cycle of the input ac voltage, diodes D2 and D4 conduct

whereas, D1 and D3 remain OFF. The conducting diodes D2 and D4 will be in series

with the load resistance RL and hence the current flows through RL in the same

direction as in the previous half cycle. Thus a bi-directional wave is converted into

unidirectional.

FIG5.3: The output waveform of the rectifier is shown as below

19

The varying DC output is suitable for lamps, heaters and standard motors. It is

not suitable for electronic circuits unless they include a smoothing capacitor.

5.4 SmoothingThe smoothing block smoothes the DC from varying greatly to a small ripple.

The ripple voltage is defined as the deviation of the load voltage from its DC value.

Smoothing is also named as filtering.

Filtering is frequently effected by shunting the load with a capacitor. The

action of this system depends on the fact that the capacitor stores energy during the

conduction period and delivers this energy to the loads during the no conducting

period. In this way, the time during which the current passes through the load is

prolong Ted, and the ripple is considerably decreased. The action of the capacitor is

shown with the help of waveform.

Fig5.4: The waveform of the rectified output after smoothing is given below:

20

5.5 RegulatorRegulator eliminates ripple by setting DC output to a fixed voltage. Voltage

regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output

voltages. Negative voltage regulators are also available Many of the fixed voltage

regulator ICs has 3 leads (input, output and high impedance). They include a hole for

attaching a heat sink if necessary. Zener diode is an example of fixed regulator which

is shown here.

Fig5.5: REGULATOR

21

Transformer + Rectifier + Smoothing + Regulator:

22

Chapter 6

BREIF DESCRIPTION ON TRIAC6.1 Introduction

Glass passivated triacs in a plastic envelope, intended for use in applications

requiring high bi-directional transient and blocking voltage capability and high

thermal cycling performance. Typical applications include motor control, industrial

and domestic lighting, heating and static switching.

Analog circuits tend to drift over time and can therefore, be Very difficult to

tune. Precision analog circuits which solve that problem, can be very large, heavy

(just think of older home stereo equipment), and expensive. Analog circuits can also

get very hot: the power dissipated is proportional to the voltage across the active

elements multiplied by the current through them. Analog circuitry can also be

sensitive to noise. Because of its infinite resolution, any perturbation or noise on an

analog signal necessarily changes the current value.

6.2 BT136Glass passivity triacs in a plastic envelope intended for use in applications

requiring high bidirectional transient and blocking voltage capability and high

thermal cycling performance. Typical applications include motor control, industrial

and domestic lighting, heating and static switching.

Pin Description

1 main terminal 1

2 Main terminal 2

3 Gate

tab Main terminal 2

23

Chapter 7

MOC30117.1 Description

The MOC301XM and MOC302XM series are optically isolated triac driver

devices. These devices contain a GaAs infrared emitting diode and a light activated

silicon bilateral switch, which functions like a triac. They are designed for interfacing

between electronic controls and power triacs to control resistive and inductive loads

for 115 VAC operations.

7.2 Features

Excellent IFT stability—IR emitting diode has low degradation

High isolation voltage—minimum 5300 VAC RMS

Underwriters Laboratory (UL) recognized—File #E90700

Peak blocking voltage

250V-MOC301 XM

400V-MOC302XM

VDE recognized (File #94766)

Ordering option V (e.g. MOC3023VM)

24

7.3 Applications

7.3.1 Driver circuit

Driver circuit consists of MOC 3011 and BT136. As the MOC 3011

used to drive the BT136 which is used to on/off the AC device using 5vdc.as

the 1st pin of MOC 3011 is anode which is given to 5vdc and the second pin is

cathode connected to the rabbit processor one of the two pins PE0 thus in the

same way another ac driver circuit is made to connect to the pe1.

One of the drivers is connected to the ac fan and other device is ac

bulb .when the client pc is operated for controlling the device appropriate

action such as on/off of the device is seen at the rabbit processor end which

the AC devices are connected. Thus in this way controlling of the devices

taken place.

25

Chapter 8

SINGLE PHASE AC MOTOR8.1 Introduction

Single-phase motors are manufactured in fractional kilowatt range to be

operated on single-phase supply and for use in numerous applications like ceiling

fans, refrigerators, food mixtures, hair driers, portable drills, vacuum cleaners,

washing machines, sewing machines, electric shavers and office machinery etc.

Single-phase motors are manufactured in different types to meet the

requirements of various applications. Single-phase motors are classified on the basis

of their construction and starting methods employed. The main types of single-phase

motors are: (a) induction motors; (b) synchronous motors; and (c) commentator

motors.

Most single-phase motors as mentioned above are fractional kilowatt motors.

But single-phase motors are also manufactured in standard integral kilowatt sizes. At

this point it may be useful to define a fractional kilowatt (FKW) motor. According to

American Standard Association (ASA) and National Engineering Manufactures

Association (NEMA) of USA, fractional kilowatt motor is a motor built in a frame

smaller than that having a continuous rating of 1kw, open type, at 1700 rpm to 1800

rpm.

According to the definition, since determination of FKW is based on frame

size, a 3/4kw, 900 rpm motor may require a bigger frame size than a 1 kw 1700 –

1800 rpm one and therefore cannot be called a fractional kilowatt motor.

8.2 Single-Phase Induction MotorsSingle-phase induction motors are similar to those of three-phase induction

motors except for the fact that the stator has a single-phase winding instead of a three-

phase winding. Performance characteristics of single-phase induction motors are less

satisfactory than three-phase induction motors. However, single-phase induction

motors have found wide range of applications where only single-phase supply is

available. Gradual improvements in design have made these motors quite satisfactory

in fractional kilowatt ratings.

26

8.3 Construction and Principle of WorkingA single-phase induction motor physically looks similar to that of a three-

phase induction motor except that its stator is provided with a single-phase winding.

The rotor construction is identical to that of a poly-phase squirrel-cage type induction

motor. In fact the rotor of any single-phase induction motor is interchangeable with

that of a poly-phase induction motor.

There is no physical connection between the rotor and the stator and there is

uniform air-gap between the stator and the rotor. The stator slots are distributed

uniformly, and usually a single-phase double-layer winding is employed.

A sample single-phase winding would produce no rotating magnetic field and

no starting torque. It is, therefore, necessary to modify or split the stator winding into

two parts, each displaced in space on the stator to make the motor self-starting.

Single-phase motors are classified into split-phase type, capacitor-type, and shaded-

pole type depending upon the starting devices employed.

Fig8.1: Squirrel Cage Induction Motor Rotor

27

8.3.1 Principle of working

A single phase induction motor with a distributed stator winding and a

squirrel cage rotor is shown below.

Φs F

Φs F

Fig8.2: Schematic construction principle of an induction machine

When single-phase supply is applied across the single-phase stator winding,

an alternating field is produced. The axis of this field is stationary in the horizontal

direction as shown in the figure. The alternating field will induce an emf in the rotor

conductors by transformer action. Since the rotor has a closed circuit, current will

flow through the rotor conductors.

28

The direction of induced emf and current in the rotor conductors is shown in

the above fig. For the direction of stator field as shown, the force experienced by the

upper conductors of the rotor will be downward and the force experienced by the

lower conductors of the rotor will be directed upward, which have been shown in

above fig. The two sets of forces will cancel and the rotor will experience no torque.

The axes of the stator and rotor magnetic fields are aligned and the torque angle is

zero. Therefore, when a single-phase supply is applied across the stator winding, the

rotor does not rotate. The worst case is if the rotor is turning at synchronous speed

then there is no relative speed difference and the rotor bars are not experiencing a

changing magnetic field therefore there can be no torque!!

It has, however, been experienced that when the rotor is given an initial

rotation in any direction, it continues to pick up speed in that particular direction. A

starting torque, therefore, is to be provided to enable the rotor to pick up speed in any

direction.

29

8.4 Speed Control The speed of single phase induction motor can be controlled only from the

stator side, since the motor has a squirrel cage rotor. The methods of speed control

which are applicable to 3-phase motor are also applicable to single-phase motor. Thus

in practice, the most important method for the rotation speed adjustment follows from

the basic equation

8.4.1 Increase of the slip

Adding resistances in the rotor circuit of the slip ring rotor machines can

increase the slip. The circle diagram of the induction machine will stay preserved, if

the resistance of the rotor R2 is increased by the addition of series resistor RV .

Hereby only the slip parameterization is changed. It is valid:

With a series resistance of and at a certain slip s2 the same circle point

and therefore the same torque and current as at the slip s1 can be obtained. So it is

possible, for example, to start up the machine with maximum torque. However, this

method has great losses because the efficiency η = 1 - s decreases.

8.4.2 Change of the number of pole pairs

In squirrel cage rotor machines, which are not bounded to a fixed pole

number, pole change alternates the rotational speed. For this purpose, two three-phase

windings with different pole numbers are placed in the stator, but only one of them

can be in operation. Alternatively, the tapped winding with possibility of pole

changing can be used. This permits a change of the rotational speed at a ratio of 2:1

by switching two coil groups from serial to parallel connection. However this method

allows to change the rotation speed only in very large steps.

30

8.4.3 Change of the supply frequency

This method requires a power converter. The power is supplied from the

three-phase network, rectified, transmitted over a DC voltage-link and fed to a power

inverter which will supply the induction machine with variable frequency and

voltage. The adjustment of frequency and voltage enables an ideal regulation of the

rotational speed with small losses. Following Fig. shows a schematic diagram of such

a device.

8.4.4 Change of applied voltage

Using an auto – transformer or Variac, any reduced voltage can be obtained.

Since speed of the motor varies with variation of applied voltage, a smooth variation

of speed can be obtained, by a gradual change of voltage.

8.4.5 Relative Motion – Slip

31

We know that, under the impact of the driving torque, the rotor is put into

motion and it begins to rotate in the same direction in which the stator magnetic field

is revolving. However, the rotor cannot rotate at synchronous speed, because, if it did

rotate at synchronous speed, then there would be no more relative motion between the

stator field and rotor, and hence no torque.

In practice, the rotor settles down to a speed slightly less than the synchronous

speed, depending on the load and internal losses.

Let N = Actual speed of the rotor (N < Ns)

The difference (N – Ns) gives the extent by which the rotor slips back from

synchronism. It is termed as ‘slip speed’ or ‘absolute slip’.

We have, Absolute slip = Ns – N.

Thus, the slip, s, defines the relative speed difference between synchronous

speed and rotor speed and is given by:

At standstill the relative speed of the rotating mmf is at a maximum,

therefore the frequency of the induced emfs is at a maximum.

Once the rotor is turning the relative speed, and hence frequency, of

the induced emf decreases.

If the rotor is turning at synchronous speed, there is no relative speed

and therefore no induced rotor emf or rotor current flow.

Therefore there is no torque produced.

This is an impossible situation that cannot be achieved by normal

motor action.

32

8.4.6 SLIP Vs SPEED

33

Chapter 9

SOFTWARE9.1 Software Components

Software used is:

*Keil software for C programming

*Express PCB for lay out design

*Express SCH for schematic design

9.1.1 KEIL µVision3

What's New in µVision3?

µVision3 adds many new features to the Editor like Text Templates, Quick

Function Navigation, and Syntax Coloring with brace high lighting Configuration

Wizard for dialog based startup and debugger setup. µVision3 is fully compatible to

µVision2 and can be used in parallel with µVision2.

9.1.1.1 What is µVision3?

µVision3 is an IDE (Integrated Development Environment) that helps you

write, compile, and debug embedded programs. It encapsulates the following

components:

A project manager.

A make facility.

Tool configuration.

Editor.

A powerful debugger.

9.1.2 Express PCB

Express PCB is a Circuit Design Software and PCB manufacturing service.

One can learn almost everything you need to know about Express PCB from the help

topics included with the programs given.

Details:

Express PCB, Version 5.6.0

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9.1.3 Express SCH

The Express SCH schematic design program is very easy to use. This software

enables the user to draw the Schematics with drag and drop options.

A Quick Start Guide is provided by which the user can learn how to use it.

Details:

Express SCH, Version 5.6.0

9.2 Embedded CThe programming Language used here in this project is an Embedded C

Language. This Embedded C Language is different from the generic C language in

few things like

a) Data types

b) Access over the architecture addresses.

The Embedded C Programming Language forms the user friendly language

with access over Port addresses, SFR Register addresses etc.

Embedded C Data types:

Data Types Size in Bits Data Range/Usage

unsigned char 8-bit 0-255

signed char 8-bit -128 to +127

unsigned int 16-bit 0 to 65535

signed int 16-bit -32,768 to +32,767

sbit 1-bit SFR bit addressable only

Bit 1-bit RAM bit addressable only

sfr 8-bit RAM addresses 80-FFH only

Signed char:

o Used to represent the – or + values.

o As a result, we have only 7 bits for the magnitude of the signed number,

giving us values from -128 to +127.

9.3 Source code

35

*PROGRAM FOR PC BASED AC MOTOR SPEED CONTROL */

#include<reg52.h>

void delay(unsigned int val);

sbit mt=P1^1; //input Ac motor

unsigned char z;

void main()

{

void delay(unsigned int val)

{

unsigned int x,y;

for(x=0;x<val;x++)

for(y=0;y<1275;y++);

}

while(1)

{

switch(P2)

{

case (0X31):

{ mt=1;

delay(10);

mt=0;

delay(90);

break;

}

case (0X32):

{ mt=1;

delay(20);

mt=0;

delay(80);

break;}

case (0X33):

{

mt=1;

delay(30);

36

mt=0;

delay(70);

break;

}

case (0X34):

{

mt=1;

delay(40);

mt=0;

delay(60);

break;

default:

{

mt=0;

}

while(1)

{

if(sw==1)

{

mt=1;

delay(50);

mt=0;

delay(50);

}

Else

{

P1=0;

mt=0;

delay(10);

mt=1;

delay(10);

} }

9.4 Flow Chart

37

START

Chapter 10

38

STOP

INITILIZATION OF DTMF OUTPUT TO PORT3

AT THE INITIAL POSSITION MOTOR IS OFF

IF(p3=2)

MOTOR ROTATES WITH LESS SPEED

MOTOR ROTATES WITH MEDIUM SPEED

MOTOR ROTATES WITH LOW SPEED

IF(p3=3)

IF(p3=4)

IF(p3=5)

MOTOR IS OFF

IF(p3=1)

MOTOR ROTATES WITH MAX SPEED SPEED

CONCLUSION AND FUTURE SCOPE10.1 CONCLUSION

The speed control of 1-Ph AC Motor has been achieved successfully using

microcontroller unit. The circuit has been tested and verified.

We used closed loop control to achieve constant speed of the Motor, for this

fixed reference speed is programmed by using the microcontroller. And the program

has been successfully tested and verified for several specified loads.

As we can obtain various speed using this program and circuitry, it replaces

the analog method applications such as

10.2 FUTURE SCOPE

In this project, we are not getting any acknowledgement whether the motor is

rotating or not. So to get acknowledgement for us, we can arrange a buzzer such that

it sounds, then we can get response through mobile when the motor gets ON or OFF.

BIBILIOGRAPHY

39

1. The 8051 Microcontroller Architecture, Programming & Applications…… Kenneth J Ayala

2. The 8051 Microcontroller & Embedded Systems…… Mohammed Ali Mazidi & Janice Gillispie Mazidi

3. Power Electronics ……. M D Singh & K B Khanchandani

4. Linear Integrated Circuits ……. D Roy Choudary & Shail Jain

5. Electrical Machines …….. S K Bhattacharya

6. Electrical Machines II …….. B L Thereja

WEB REFERENCE:

1. WWW.FRANKLIN.COM

2. WWW.KEIL.COM

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