“THERMAL OVERLOAD RELAY USING LABVIEW”

Project report submitted in partial fulfillment of the requirements

For the award of the degree of

BACHELOR OF TECHNOLOGY

IN

ELECTRICAL AND ELECTRONICS ENGINEERING

By

Abhishek.ch 08241A0201

K. Naresh 08241A0227

P. Ravi Kumar 08241A0238

B.Satyanarayana 09245A0209

Under the guidance of

Sarfaraz Nawaz Syed

Assistant Professor

Department of Electrical and Electronics Engineering GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING &

TECHNOLOGY, BACHUPALLY, HYDERABAD-72 2008 – 2012

GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND

TECHNOLOGY

Hyderabad, Andhra Pradesh.

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

CERTIFICATE

This is to certify that the project report entitled “THERMAL OVERLOAD RELAY USING

LABVIEW” that is being submitted by Abhishek.ch, K. Naresh, P.Ravi Kumar,

B.Satyanarayana in partial fulfillment for the award of the Degree of Bachelor of Technology

in Electrical and Electronics Engineering to the Jawaharlal Nehru Technological University is

a record of bonafide work carried out by them under my guidance and supervision. The results

embodied in this project report have not been submitted to any other University or Institute for

the award of any Graduation degree.

Prof.P.M. Sarma External Mr. Sarfaraz Nawaz Syed

HOD, EEE Assistant Professor, EEE Dept.

GRIET, Hyderabad GRIET, Hyderabad

(Project Guide)

ACKNOWLEDGEMENT

This is to place on record, my appreciation and deep gratitude to the persons without

whose support this project would never see its design-level aspect and its success.

I have immense pleasure in expressing my thanks and deep sense of gratitude to my

guide Mr. Sarfaraz Nawaz Syed, Assistant Professor, Department of Electrical and

Electronics Engineering, G.R.I.E.T for his guidance throughout this project.

I also express my sincere thanks to Prof. P.M. Sharma, Head of the Department, and

G.R.I.E.T for his ever-lasting, success driven guidance, all through the acute prob-

lems faced during the project work.

I express my gratitude to Dr. S.N. Saxena, Professor, Department of Electrical and

Electronics Engineering, Coordinator, Project Review Committee, G.R.I.E.T for his

valuable recommendations and for accepting this project report.

Finally I express my sincere gratitude to Mr. Shiva Kumar, Assistant Professor,

Ms. Madhuri, Assistant Professor, Department of Electrical and Electronics Engi-

neering, G.R.I.E.T and all the members of faculty and my friends who contributed

their valuable advice and helped to complete the project successfully.

ABSTRACT

Thermal overload relay using labVIEW is the project which makes use of labVIEW to monitor and

control operation of the electrical machine. The real time variables of electrical machine are meas-

ured and given to labVIEW through DAQ.

LabVIEW allows us to program as per our requirements. We continuously observe the operating

temperature and Trip the circuit if the temperature exceeds a safe value. Ambient working tempera-

ture of the machine is taken as safe value of temperature.

The temperature rise is calculated based on the machine temperature constant (degree centigrade per

kilowatt). A comparison has been made such that the temperatures above safe value would turn on an

LED emitting red light. When the light glows, a digital signal of 5V is generated at the selected line

on DAQ. This 5V is drawn into the relay arrangement, which is used to energized itself and trip the

contact, hence isolating the machine from the main supply

A Data Acquisition Card (DAQ) is used to perform the core of the control action by switching

ON the relay. The DAQ, USB 6009 is selected for this project. In order to provide precise input vol-

tages to the DAQ, such that change in each degree of temperature is observable, the current is read to

the DAQ through current transformer.

A suitable logic using is written into the DAQ in the LabVIEW. Observing the voltages that are ob-

tained from the current transformer the relay is operated. When the temperature exceeds 40 degree

centigrade the relay is operated.

I

ABBREVIATIONS

GND - Ground

DAQ - Data Acquisition

LabVIEW - Laboratory Visual Instrumentation Engineering Workbench

NI - National Instruments

IC - Integrated Circuit

PCB - Printed Circuit Board

TTL - Transistor-Transistor Logic

IO - Input-Output

RAM - Random Access Memory

ADC - Analog to Digital Converter

DAC - Digital to Analog Converter

PC - Personal Computer

USB - Universal Serial Bus

PCI - Peripheral Component Interconnect

VI - Visual Interactive

FPGA - Field Programmable Gate Array

LED - Light Emitting Diode

II

CONTENTS

LIST OF FIGURES

LIST OF TABLES

CHAPTER 1: INTRODUCTION 1

1.1 NEED FOR TEMPERATURE CONTROL 1

1.2 MACHINE USED IN PROJECT 2

CHAPTER 2: OVERVIEW OF THE PROJECT 3

2.1 BLOCK DIAGRAM 4

2.2 CONTROL LOGIC 4

CHAPTER 3: CURRENT TRANSFORMER 6

3.1 DESIGN 6

3.2 TYPES OF CURRENT TRANSFORMERS 7

CHAPTER 4: DATA ACQUISITION (DAQ USB-6009) 9

4.1 EASE OF OPERATION 10

4.2 ADVANTAGES OVER OTHER CONTROL

INTERFACES 17

4.3 INTERFACING DAQ WITH LABVIEW 18

4.4 LABVIEW PROGRAMMING 20

III

CHAPTER 5: FINAL HARDWARE IMPLEMENTATION 25

5.1 INTERFACING THE CURRENT TRANSFOR-

MER WITH DAQ 25

5.2 CORRESPONDING LABVIEW PROGRAM 26

5.3 CALCULATION OF TEMPERATURE

RISE CONSTANT ‘K’ (*C/KW) 30

5.4 FINAL HARDWARE SETUP 33

CHAPTER 6: SCOPE FOR FUTURE DEVELOPMENT 34

REFERENCES 35

APPENDIX

IV

LIST OF FIGURES

Fig 2.1a block diagram 2

Fig 2.2a 5 pin relay 3

Fig 3.1a current transformer 5

Fig 4.1a process of data acquisition 14

Fig 4.1b ease of access of NI-DAQ 15

Fig 4.3a interfacing with labVIEW 18

Fig 4.4a input module menu for programming 19

Fig 4.4b DAQ assistant initial analysis 20

Fig 4.4c while loop structure in labVIEW programming 23

Fig 5.1a USB-6009 control panel 24

Fig 5.2a labVIEW program 26

Fig 5.2b display under normal conditions 27

Fig 5.2c display under overload conditions 28

Fig 6 Final Hardware setup 32

LIST OF TABLES:

Table 5.3a Determination of machine temperature rise constant ‘K’ 31

V

CHAPTER 1

INTRODUCTION

1.1 NEED FOR TEMPERATURE CONTROL

The main reason behind the temperature control is to avoid the breakdown of insulation in the

winding and the effect of appreciable resistance rise .The overheating generally occurs when the mo-

tor is overloaded, a bearing seizes up, something opposing the motor shaft from turning, or the motor

simply fails to start properly. A failure to start may be caused by faulty start windings in a motor.

Just because a motor fails to start or overheats during operation, doesn't mean that the motor is neces-

sarily at fault. There could be an obstruction on the attached load to the motor, causing excessive

load on the motor. This in turn causes excessive heat to build up in the motor and hopefully, the

thermal protector trips the motor circuit to save the motor.

A good example of this is a sump pump, that probably everyone has used at one time or another. Im-

agine that the sump pump is pumping dirty water with sticks and who knows what all out of a sump

pump hole. Suddenly, a piece of a stick gets caught in the impeller of the pump and locks the rotation

of the pump motor. It keeps the motor from turning and causes the motor to heat very quickly. Sud-

denly the thermal protector trips and shuts the circuit down to the motor windings. This allows the

motor to cool and saves the motor. Unfortunately, the water is no longer pumping, but it obviously

wouldn't have anyway and you'd likely be changing the sump pump out, rather than just cleaning out

the obstruction. That's not to say the pump motor hasn't gone bad, as they often fail from hours of

use.

1

1.2 MACHINE USED IN THE PROJECT

Single phase Induction motor

Power 750w,

Speed 1425rpm

Voltage 230v,

1-phase, 50hz

Current 7.5A

Start Capacitor 120uf, 275v

Ambient Temp 40*c

2

CHAPTER 2

OVERVIEW OF THE PROJECT

2.1 BLOCK DIAGRAM

Fig 2.1a

Above block diagram shows the chronological occurrences of the processes that are to be

Carried out in order to protect the machine from overload.

Also, the sequence of equipment used in the entire control process is as listed in the block diagram.

The flow from each sequence to the next sequence is also clearly shown in the block diagram.

3

INDUCTION

MOTOR

CURRENT

TRANSFOEMER

DAQ

USB 6009

LABVIEW

RELAY

The current transformer first senses the current and gives out a corresponding voltage, which goes to

the input terminals of the DAQ USB-6009.This voltage is read by LabVIEW and analysis has been

made over it and other manipulations were added, so as to provide the apt control logic. The output

terminals of the DAQ are given to relay which were able to isolate the machine from the main

supply.

2.2 CONTROL LOGIC:

1 3

2 4 5

Fig 2.2a

5 pin relay

Relay operation:

All relays operate using the same basic principle. In our project we use 5 pin relay as shown in the

above figure. Relays have two circuits: A control circuit and the load circuit. The control circuit has a

small control coil and the load circuit has a switch. The coil controls the operation of the switch.

4

Relay energized (ON):

Current flowing through the control coil (pins 1 and 2) creates a small magnetic field which causes

the switch to close, pins 3 and 4. The switch, which is the part of the load circuit, is used to control

an electrical circuit which is connected to it. Current now flows through pins 3 and 4 when the relay

is energized.

Relay de-energized (OFF):

When current stops flowing through the control circuit, pins 1 and 2, the relay becomes de-energized.

Without magnetic field, the switch gets opened to the line 3 and 4; hence the current through the pins

3 and 4 is halted.

5

CHAPTER 3:

CURRENT TRANSFORMER

3.1 DESIGN

Figure 3.1aCurrent transformer

Like any other transformer, a current transformer has a primary winding, a magnetic core, and a sec-

ondary winding. The alternating current flowing in the primary produces a magnetic field in the core,

which then induces a current in the secondary winding circuit. A primary objective of current trans-

former design is to ensure that the primary and secondary circuits are efficiently coupled, so that the

secondary current bears an accurate relationship to the primary current.

The most common design of CT consists of a length of wire wrapped many times around a silicon

steel ring passed over the circuit being measured. The CT's primary circuit therefore consists of a

single 'turn' of conductor, with a secondary of many tens or hundreds of turns. The primary winding

may be a permanent part of the current transformer, with a heavy copper bar to carry current through

the magnetic core. Window-type current transformers are also common, which can have circuit

cables run through the middle of an opening in the core to provide a single-turn primary winding.

6

When conductors passing through a CT are not centered in the circular (or oval) opening, slight inac-

curacies may occur.

Shapes and sizes can vary depending on the end user or switchgear manufacturer. Typical examples

of low voltage single ratio metering current transformers are either ring type or plastic molded case.

High-voltage current transformers are mounted on porcelain bushings to insulate them from ground.

Some CT configurations slip around the bushing of a high-voltage transformer or circuit breaker,

which automatically centers the conductor inside the CT window.

The primary circuit is largely unaffected by the insertion of the CT. The rated secondary current is

commonly standardized at 1 or 5 amperes. For example, a 4000:5 CT would provide an output cur-

rent of 5 amperes when the primary was passing 4000 amperes. The secondary winding can be single

ratio or multi ratio, with five taps being common for multi ratio CTs. The load, or burden, of the CT

should be of low resistance. If the voltage time integral area is higher than the core's design rating,

the core goes into saturation towards the end of each cycle, distorting the waveform and affecting

accuracy

7

3.2 TYPES OF CURRENT TRANSFORMERS

Current transformers (CT's) provide a simple, inexpensive and yet accurate means of

Sensing current flow in power conductors. They are available in 3 basic configurations:

1. Ring Core CT's are available for measuring currents from 50 to 5000 amps, with windows

(power conductor opening size) from 1" to 8” diameter.

2. Split Core CT's are available for measuring currents from 100 to 5000 amps, with windows

in varying sizes from 1" by 2" to 13" by 30". Split core CT's have one end removable so that the

load conductor or bus bar does not have to be disconnected to install the CT.

3. Wound Primary CT's are designed to measure currents from 1 amp to 100 amps. Since

the load current passes through primary windings in the CT, screw terminals are provided for the

load and secondary conductors. Wound primary CT's are available in ratios from 2.5:5 to 100:5

(Models 189 and 190 are examples of wound primary CT's).

CT's used with watt transducers enable the owner to control demand as well as monitor building

and/or tenant power consumption. When CT's are used with Current

Transducers, the result are an excellent method of diagnosing the performance of fans, Pumps,

chillers, etc.

Current Transducers provide alarms for each motor so the owner is warned immediately of any

abnormal operating condition. Low pump flows will be alarmed if the strainer is dirty or the

coupling is broken. Low fan flows will be alarmed if filters are dirty, belts are slipping, or dam-

pers (fire, smoke, etc.) are closed.

8

Chapter 4

DATA ACQUISITION (DAQ USB-6009)

4.1 EASE OF OPERATION:

Data acquisition (DAQ) is the process of measuring an electrical or physical phenomenon such

as voltage, current, temperature, pressure, or sound. PC-based data acquisition uses a combina-

tion of modular hardware and flexible software to transform your standard laptop or desktop

computer into a user- defined measurement or control system. Learn more about each of these

components in the sections below.

While each data acquisition system has unique functionality to serve application- specific re-

quirements, all systems share common components that include signals, sensors, signal condi-

tioning, DAQ hardware, and a computer with software.

Data acquisition is the process of sampling signals that measure real world physical conditions

and converting the resulting samples into digital numeric values that can be manipulated by a

computer. Data acquisition systems (abbreviated with the acronym DAS or DAQ) typically con-

vert analog waveforms into digital values for processing. The components of data acquisition

systems include:

• Sensors that convert physical parameters to electrical signals.

• Signal conditioning circuitry to convert sensor signals into a form that can be converted

to digital values.

• Analog-to-digital converters, which convert conditioned sensor signals to digital values.

Data acquisition applications are controlled by software programs, developed

• Using various general purpose programming languages such as BASIC, C, FORTRAN,

Java, Lisp, and Pascal.

9

Source

Data acquisition begins with the physical phenomenon or physical property to be measured.

Examples of this include temperature, light intensity, gas pressure, fluid flow, and force.

Regardless of the type of physical property to be measured, the physical state that is to be meas-

ured must first be transformed into a unified form that can be sampled by a data acquisition sys-

tem. The task of performing such transformations falls on devices called sensors.

A sensor, which is a type of transducer, is a device that converts a physical property into a cor-

responding electrical signal (e.g., a voltage or current) or, in many cases, into a corresponding

electrical characteristic (e.g., resistance or capacitance) that can easily be converted to electrical

signal.

The ability of a data acquisition system to measure differing properties depends on having sen-

sors that are suited to detect the various properties to be measured. There are specific sensors for

many different applications. DAQ systems also employ various signal conditioning techniques to

adequately modify various different electrical signals into voltage that can then be digitized us-

ing an Analog-to-digital converter (ADC).

DAQ Hardware

DAQ hardware is what usually interfaces between the signal and a PC. It could be in the form of

modules that can be connected to the computer's ports (parallel, serial, USB, etc.) or cards con-

nected to slots in the mother board. Usually the space on the back of a PCI card is too small for

all the connections needed, so an external breakout box is required. The cable between this box

and the PC can be expensive due to the many wires, and the required shielding.

DAQ cards often contain multiple components (multiplexer, ADC, DAC, TTL-IO, high speed

timers, RAM). These are accessible via a bus by a microcontroller, which can run small pro-

grams. A controller is more flexible than a hard wired logic, yet cheaper than a CPU so that it is

permissible to block it with simple polling loops. For example: Waiting for a trigger, starting the

ADC, looking up the time, waiting for the ADC to finish, move value to RAM, switch multip-

lexer, get TTL input, let DAC proceed with voltage ramp.

Many times reconfigurable logic is used to achieve high speed for specific tasks and digital sig-

nal processors are used after the data has been acquired to obtain some results.

10

The fixed connection with the PC allows for comfortable compilation and debugging. Using an

external housing a modular design with slots in a bus can grow with the needs of the user.

Not all DAQ hardware has to run permanently connected to a PC, for example intelligent stand-

alone loggers and oscilloscopes, which can be operated from a PC, yet they can operate com-

pletely independent of the PC.

Signals

Signals may be digital (also called logic signals sometimes) or analog depending on the trans-

ducer used. Signal conditioning may be necessary if the signal from the transducer is not suitable

for the DAQ hardware being used. The signal may need to be amplified, filtered or demodulated.

Various other examples of signal conditioning might be bridge completion, providing current or

voltage excitation to the sensor, isolation, and linearization. For transmission purposes, single

ended analog signals, which are more susceptible to noise, can be converted to differential sig-

nals. Once digitized, the signal can be encoded to reduce and correct transmission errors.

Signal Conditioning

Sometimes transducers generate signals too difficult or too dangerous to measure directly with a

data acquisition device. For instance, when dealing with high voltages, noisy environments, and

extreme high and low signals, or simultaneous signal measurement, signal conditioning is essen-

tial for an effective data acquisition system. It maximizes the accuracy of a system, allows sen-

sors to operate properly, and guarantees safety Amplification.

Amplifiers increase voltage level to better match the analog-to-digital converter (ADC) range,

thus increasing the measurement resolution and sensitivity. In addition, using external signal

conditioners located closer to the signal source, or transducer, improves the measurement signal-

to-noise ratio by magnifying the voltage level before it is affected by environmental noise.

11

Attenuation

Attenuation, the opposite of amplification, is necessary when voltages to be digitized are beyond

the ADC range. This form of signal conditioning decreases the input signal amplitude so that the

conditioned signal is within ADC range. Attenuation is typically necessary when measuring vol-

tages that are more than 10 V.

Isolation

Isolated signal conditioning devices pass the signal from its source to the measurement device

without a physical connection by using transformer, optical, or capacitive coupling techniques.

In addition to breaking ground loops, isolation blocks high-voltage surges and rejects high com-

mon-mode voltage and thus protects both the operators and expensive measurement equipment.

Filtering

Filters reject unwanted noise within a certain frequency range. Oftentimes, low pass filters are

used to block out high-frequency noise in electrical measurements, such as 60 Hz power. Anoth-

er common use for filtering is to prevent aliasing from high-frequency signals. This can be done

by using an antialiasing filter to attenuate signals above the Nyquist frequency.

Excitation

Excitation is required for many types of transducers. For example, strain gages, accelerometers

thermistors, and resistance temperature detectors (RTDs) require external voltage or current exci-

tation. RTD and thermistor measurements are usually made with a current source that converts

the variation in resistance to a measurable voltage. Accelerometers often have an integrated am-

plifier, which requires a current excitation provided by the measurement device. Strain gages,

which are very-low-resistance devices, typically are used in a Wheatstone bridge configuration

with a voltage excitation source.

Linearization

Linearization is necessary when sensors produce voltage signals that are not linearly related to

the physical measurement.

12

Linearization is the process of interpreting the signal from the sensor and can be done either with

signal conditioning or through software. Thermocouples are the classic example of a sensor that

requires linearization.

Cold-Junction Compensation

Cold-junction compensation (CJC) is a technology required for accurate thermocouple measure-

ments. Thermocouples measure temperature as the difference in voltage between two dissimilar

metals. Based on this concept, another voltage is generated at the connection between the ther-

mocouple and terminal of your data acquisition device. CJC improves your measurement accura-

cy by providing the temperature at this junction and applying the appropriate correction.

Bridge Completion

Bridge completion is required for quarter- and half-bridge sensors to comprise a four resistor

Wheatstone bridge. Strain gage signal conditioners typically provide half-bridge completion net

works consisting of high-precision reference resistors. The completion resistors provide a fixed

reference for detecting small voltage changes across the active resistor(s).

Hardware aspects of DAQ

Data acquisition hardware acts as the interface between a computer and signals from the outside

world. It primarily functions as a device that digitizes incoming analog signals so that the com-

puter can interpret them. Data acquisitions devices typically consist of one or more of the follow-

ing functions for measuring different types of signals:

• Analog inputs – measure analog signals

• Analog outputs – generate analog signals

• Digital inputs/outputs – measure and generate digital signals

• Counter/timers – count events or generate pulses

13

Multifunction data acquisition boards combine analog, digital, and counter operations on a single

device. Data acquisition hardware is offered on several different PC busses. Each bus offers dif-

ferent levels of ease-of-use and performance and is better suited for different applications.

Computer/Software

Unlike traditional instruments, a computer is a required component in a data acquisition system.

Because of this, a user can take advantage of the ever-increasing performance of the computer’s

processor, hard drive, and display for taking measurements, visualizing data, performing analy-

sis, and storing data.

Software

Software is what transforms the PC and the data acquisition hardware into a complete data ac-

quisition, analysis, and presentation tool. Without software to control or drive the hardware, the

data acquisition device does not work properly.

Driver Software

Driver software is the layer of software for easily communicating with the hardware. It forms the

middle layer between the application software and the hardware. Driver software also prevents a

programmer from having to do register-level programming or complicated commands to access

the hardware functions.

Application Software

The application layer can be either a development environment in which you build a custom ap-

plication that meets specific criteria, or it can be a configuration-based program with preset func-

tionality. Application software adds analysis and presentation capabilities to driver software. To

choose the right application software, evaluate the complexity of the application, the availability

of configuration-based software that fits the application, and the amount of time available to de-

velop the application. If the application is complex or there is no existing program, use a devel-

opment environment.

14

The complete process of the Data Acquisition is as per the following block diagram:

Figure 4.1a

Improved Productivity through Software

One of the biggest benefits of using a PC-based data acquisition device is that you can use soft-

ware to customize the functionality and visualization of your measurement system to meet your

application needs. When examining the cost of building a data acquisition system, software de-

velopment often accounts for 25 percent of total system cost. Obtaining easy-to-use driver soft-

ware with an intuitive application programming interface makes a big impact on completing a

project on time and under budget. National Instruments provides awide array of software tools

that make you more productive at accomplishing your measurement or automation tasks.

• NI-DAQmx Driver Software

• NI LabVIEW Graphical Programming

NI-DAQmx Driver Software

NI-DAQmx driver software goes far beyond a basic DAQ driver to deliver increased productivi-

ty and performance and is one of the main reasons National Instruments continues to be the lead-

er in virtual instrumentation and PC-based data acquisition.

15

One Interface, Many Programming Languages

NI-DAQmx provides the same interface for many popular programming languages including

NI LabVIEW, Visual Studio .NET languages, C, and C++. The functions and properties, as well

as the order of the functions you use, are the same across all languages.

One Interface, Hundreds of Data Acquisition Devices

Whether you are developing with a PCI, PCI Express, PXI, PXI Express, USB, Ethernet, or

Wireless data acquisition device, the basic NI-DAQmx code is the same across all devices.

With a single programming interface, you can easily upgrade or switch hardware without chang-

ing your code.

Easy and Powerful Data Acquisition Software

NI-DAQmx includes intuitive features to make taking measurements easier, as well as powerful

features to give you higher performance and more flexibility.

Figure 4.1b

16

4.2 ADVANTAGES OVER OTHER CONTROL INTERFACES

NI data acquisition devices designed for performance by providing high-performance I/O,

Industry-leading technologies and software-driven productivity gains for your application.

With patented hardware and software technologies, National Instruments offers a wide spectrum

of PC-based measurement and control solutions that deliver the flexibility and performance that

your application demands. For more than 25 years, National Instruments has served as more than

just an instrument vendor, but as a trusted advisor to engineers and scientists around the world.

High-Performance I/O

Measurement accuracy is arguably one of the most important considerations in designing any

data acquisition application. Yet equally important is the overall performance of the system, in-

cluding I/O sampling rates, throughput, and latency. For most engineers and scientists, sacrific-

ing accuracy for throughput performance or sampling rate for resolution is not an option. Nation-

al Instruments wide selection of PC-based data acquisition devices have set the standard for ac-

curacy, performance, and ease-of-use from PCI to PXI and USB to wireless.

High-Accuracy Designs

Many scientists and engineers mistakenly evaluate DAQ device error by just considering the bit

resolution of the DAQ device. However, the error dictated by the device resolution, or quantiza-

tion error, might account for only a very small amount of the total error in your measurement re-

sult. Other types of errors, such as temperature drift, offset, gain, and nonlinearity can vary dras-

tically by hardware design. Through years of experience, NI has developed several key technol-

ogies to minimize these errors and maximize the absolute accuracy of your measurements.

17

Easy Sensor Connectivity with Integrated Signal Conditioning

Traditionally, measuring sensors required separate front-end signal conditioning systems cabled

to a data acquisition system. New technologies and miniaturization have enabled the integration

of sensor-specific signal conditioning and analog to digital conversion on the same device.

NI DAQ devices with integrated signal conditioning deliver higher-accuracy measurements by

eliminating error-prone cabling and connectors and reduce the number of components in a mea-

surement system.

I/O for Any Sensor, Any Bus

The breadth and depth of National Instruments product offering is not available from any other

vendor. NI DAQ devices are offered on a variety of common PC-busses including USB, PCI,

PCI Express, PXI, PXI Express, Wi-Fi (IEEE 802.11), and Ethernet, with a wide spectrum of

measurement types. NI’s modular form factors provide interchangeability to meet your specific

application’s needs and the flexibility for future expansion.

4.3 INTERFACING DAQ WITH LABVIEW

NI LabVIEW Graphical Programming

NI LabVIEW is a graphical programming environment that makes it easy to take any measurement

from any sensor on any bus. You can automate measurements from several devices, analyze data in

parallel with acquisition, and create custom reports all in a matter of minutes with this industry-

standard tool. From acquiring one simple measurement to capturing data from a complex 10,000-

channel system, LabVIEW can help you acquire, analyze, and log data in less time.

18

Fig 4.3a Interfacing with labVIEW

Work Faster with a Graphical Approach

With LabVIEW, you develop data acquisition applications using drag-and-drop graphical icons

instead of writing lines of text. You can complete programs that take weeks to write with tradi-

tional programming languages in hours using LabVIEW, even if you have no programming ex-

perience. An intuitive flowchart representation displays your code in a manner that is easy to de-

velop, maintain, and understand.

Get Started Immediately with Open-and-Run Examples

There is no need to create your entire data acquisition system from scratch. LabVIEW includes

several shipping examples for every common measurement task. Hit the ground running with

open-and-run programs for virtually any setup, ranging from a simple single-channel measure-

ment to a high-performance multichannel system featuring advanced timing, triggering, and syn-

chronization across multiple devices.

19

Create a Professional User Interface in Seconds

LabVIEW helps you quickly create a graphical user interface using hundreds of drag-and-drop

controls, graphs, and 3D visualization tools. You can customize the position, size, alignment,

scale, and color of these built-in controls in a matter of seconds from a right-click menu. Lab-

VIEW also helps you create your own controls or incorporate custom imagery and logos.

4.4 LABVIEW PROGRAMMING

Using Configuration-Based Programming

LabVIEW distinguishes Express VIs with large blue icons. When you place an Express VI on the

block diagram, a dialog appears so you can configure how the function executes. After completing

the configuration, the LabVIEW development environment writes the necessary code (represented by

the Express VI) for you. You can view and modify this code, and you can change the Express VI

configuration by simply double-clicking the Express VI icon.

Figure 4.4a

20

Input module menu for programming

Consider the task of reading real-world signals into software for analysis. LabVIEW is designed to

make integration with hardware for I/O simple and easy thanks to native drivers and support for

thousands of instruments. However, even a task that would otherwise take a handful of VIs to ex-

ecute can be simplified to a single Express VI. The DAQ Assistance

Figure 4.4b

DAQ assistant initial analysis

21

Express VI prompts you to select the channels you want to send and receive I/O to and from, and

configure parameters such as sample rate, terminal configuration, scales, triggering, and synchroniza-

tion. You also can preview the data within the interface before saving the configuration.

Express VIs does not offer the same low-level control as VIs, which is why you may prefer to write

the code entirely using VIs.

New users interested in learning low-level constructs can easily convert an Express VI to the under-

lying G code by right-clicking the Express VI and selecting Open Front Panel. Normal VIs can do

everything an Express VI can do. The LabVIEW Professional Development System also includes a

utility for creating custom Express VIs.

Taking Advantage of Flexible Programming

The combination of multiple programming approaches in a single development environment of-

fers the advantage of reusing existing code and algorithms developed in other languages. It also

makes it possible to combine simple, high-level abstractions with lower-level code that gives you

more visibility and control of your application. These abstraction layers represent highly com-

plex operations in simple, easy-to-read representations, but can be coupled with functions that

give low-level control over application behavior and hardware interfaces. Thanks to tight inte-

gration with I/O, you can combine these approaches with real-world signals to take advantage of

the most recent hardware technology such as multi-core CPUs, FPGAs, and

embedded processors.

Signal processing applications developed in LabVIEW make frequent use of basic constructs that

are common to all high-level programming languages: for-loops, while-loops, and case struc-

tures. A For Loop repeats a block of code a fixed number of times, a While Loop repeats a block

of code as long as a particular condition is true, and a Case Structure executes one of several

blocks of code depending on some selection criterion. After completing this module you will be

able to use these three essential structures in your own LabVIEW Vis.

While-Loop Structure

The While Loop structure is similar to the For Loop structure with its ability to repeatedly run a

sub diagram, but the number of times is not fixed in advance. Instead, the while-loop structure

will execute its sub diagram as long as a particular condition is true. The following screen shot

will show you how to use the While Loop structure.

22

The While Loop executes the sub diagram until the conditional terminal, an input terminal, rece-

ives a specific Boolean value. The default behavior and appearance of the conditional terminal is

Stop if True, shown as follows.

When a conditional terminal is Stop if True, the While Loop executes its sub diagram until the

conditional terminal receives a TRUE value. You can change the behavior and appearance of the

conditional terminal by right-clicking the terminal or the border of the While Loop and selecting

Continue if true, shown as follows, from the shortcut menu.

When a conditional terminal is Continue if True, the While Loop executes its subdiagram until

the conditional terminal receives a FALSE value. You also can use the Operating tool to click

the conditional terminal to change the condition. If you place the terminal of the Boolean control

outside the While Loop, as shown in the following figure, and the control is set to FALSE if the

conditional terminal is Stop if True when the loop starts, you cause an infinite loop. You also

cause an infinite loop if the control outside the loop is set to TRUE and the conditional terminal

is Continue if True. Changing the value of the control does not stop the infinite loop because the

value is only read once, before the loop starts. To stop an infinite loop, you must abort the VI by

clicking the Abort Execution button on the toolbar.

You also can perform basic error handling using the conditional terminal of a While Loop.

When you wire an error cluster to the conditional terminal, only the TRUE or FALSE value of

the status parameter of the error cluster passes to the terminal. Also, the Stop if True and

Continue if True shortcut menu items change to stop if Error and Continue while Error.

23

Figure 4.4c

While loop structure in labVIEW programming

24

Chapter 5

FINAL HARDWARE IMPLEMENTATION

5.1 INTERFACING THE CURRENT TRANSFORMER WITH

DAQ.

The NI DAQ USB-6009 is designated with 8 analog inputs and 2 analog outputs. Although, this

DAQ consists of digital input-output ports, analog ports are most desired as of now, as they are

the required ports to access the voltage coming in from the temperature sensor.

After successfully initializing the DAQ assistant, following control panel can be observed, where

all the required control logic can be given-in and also, respective indicators can be allotted, so as

to view their working status. Figure 5.1a USB-6009 CONTROL PANEL

25

For this current project, two terminals are required for the output to be drawn out and displayed,

one being the output voltage terminal, and the other being the corresponding ground terminal.

Now referring to above figure, a ground terminal must be selected and the ground terminal re-

spective to the output voltage of the current transformer must be coupled.

Correspondingly, the output voltage terminal has to be connected to any of the analog input

Terminals of the DAQ, thereby concluding the process of making the hard-wire connections, to

enable the opportunity to display the output and thereby proceed with control logic system.

The above described process, at the end would appear as shown in the following figure.

Another important connection of the DAQ USB-6009 with the PC has to be made using the

Provided cable, through which the communication between the PC and the DAQ would be Poss-

ible to display the output and to further take any control action.

5.2 CORRESPONDING LABVIEW PROGRAM

The entire control logic to have been implemented in the project was made possible with the use

of LabVIEW programming with its simple block-diagram approach in building the entire logic.

Viewing it step-wise, the output of the current transformer arrangement, which is read-in by the

DAQ, is of the order 3.3V to 5.5V. A suitable multiplying factor has been formulated such that,

the read voltages between 3.3V and 5.5V directly represent the temperature actually sensed by

the temperature sensor.

The so obtained current value which would be displayed and further used for control logic pur-

pose is more or less, accurately calibrated.

26

Fig 5.2 a

LabVIEW program

27

Fig 5.2b

Display under normal conditions

28

Fig 5.2c

Display under overload conditions

A comparison has been made such that the temperatures above 40 degrees centigrade would turn

on an LED emitting red light. When the light glows, a digital signal of 5V is generated at the se-

lected line on DAQ. This 5V is drawn into the relay arrangement, which is used to energized itself

and trip the contact, hence isolating the machine from the main supply.

29

5.3: CALCULATION OF TEMPERATURE RISE CONSTANT ‘K’

(*C/KW/Sec)

What is K?

Machine operating temperature increases as it is loaded.

K is the temperature rise constant of the given machine. K tells about how machine operating

temperature increases when it is loaded gradually.

Units of K is *C/kw/sec.

Methods of Finding K:

1. Measurement of Resistance method

2. Using Digital Thermometer

I. Measurement of Resistance method

Measurement of Resistance method is an indirect method. In this method Resis-

tance of winding is measurement at different loading levels. By knowing Temperature coeffi-

cient of Resistance of the winding, we can calculate the temperature rise.

Disadvantages:

� Change in resistance is very small.

� High Resolution of Resistance measurement is required.

30

Formula:

R=Rref [1+α (T-Tref )]

Where

R = conductor resistance at temperature “T”

Rref = conductor resistance at reference temperature Tref , usually 20* c, but sometimes 0*c.

α = Temperature coefficient of resistance for the conductor material.

T = Conductor temperature in degree Celsius.

Tref = Reference temperature that α is specified at for the conductor material.

II. Digital Thermometer Method:

It is the simplest method to find out the K. It is the direct method of finding K.

In this method Digital thermometer probe is placed on the machine winding itself.

Temperature of winding is noted at different level of loading and also corresponding amount of

load is also observed. Tabular form is formed with these observations.

Finally graph is plotted for Temperature as a function of load. Obtained graph is linearised.

Slope the linearised plot is the Value of K in (°C/kw/sec).

31

OBSERVATIONS:

V(volts) I(Amps) P(kw) Temp(In °°°°C) Duration(mins)

61 1.07 .01 28.3 5

120 2.02 .03 30.9 5

165 3.05 .08 32.9 5

200 4.07 .12 36.2 5

223 5.02 .2 40.9 5

240 6.10 .29 48 5

Table 5.3a

Results:

Initial Temperature To =27.4oc

Finally K=.12oc/kw/sec.

32

FINAL HARDWARE SETUP

Fig 6

33

CHAPTER 6

SCOPE FOR FUTURE DEVELOPMENT

This project aimed at providing protection to the machine from thermal overloading .This project can

be used for many faults which are sensed by temperature measurement.

Choosing better temperature ICs like LM35 which would include much higher range of temperatures

in their sensing and accuracy tables would be one incentive to proceed and bring development to this

project.

ICs used for amplification could also be more aptly selected for other challenging environments pro-

vided and to be fulfilled.

For overload protection of large scale machines this project is to be modified by introducing LM35

temperature sensor. The actual operating temperature of the machine is monitored continuously and

that is compared with the safe value of temperature limit.

This project not only provides overload protection but also provides protection over wide range of

faults whose presence can be known by temperature measurement.

For electrical machines like Oil immersed type of Transformers more than 90% of faults are sensed

through rise in oil temperature. Generally Buchholz relay is used for this purpose in oil immersed trans-

formers. This project can be used in conjunction with Buchholz relay to provide a more effective and reliable

method of protection.

34

REFERENCES 1. Muhammad H. Rashid, Micro electric Circuits: Analysis and Design, 114-125, Cengage

Learning, 2010.

2. Bill Urmenyi, Electronics for Artists, 91-94, Bill Urmenyi Ltd., 2001.

3. National Instruments, NI-USB 6009, http://sine.ni.com/psp/app/doc/p/id/psp-115/lang/en

4. National Instruments, NI LabVIEW, www.ni.com/labview

35

APPENDIX A :

Current transformers (CT's) provide a simple, inexpensive and yet accurate means of

sensing current flow in power conductors. They are available in 3 basic configurations:

1. Ring Core CT's are available for measuring currents from 50 to 5000

amps, with windows (power conductor opening size) from 1" to 8"

diameter.

2. Split Core CT's are available for measuring currents from 100 to 5000

amps, with windows in varying sizes from 1" by 2" to 13" by 30". Split

core CT's have one end removable so that the load conductor or bus bar

does not have to be disconnected to install the CT.

3. Wound Primary CT's are designed to measure currents from 1 amp to

100 amps. Since the load current passes through primary windings in the

CT, screw terminals are provided for the load and secondary conductors.

Wound primary CT's are available in ratios from 2.5:5 to 100:5 (Models

189 and 190 are examples of wound primary CT's).

CT's used with watt transducers enable the owner to control demand as well as monitor

building and/or tenant power consumption. When CT's are used with Current

Transducers, the result is an excellent method of diagnosing the performance of fans,

pumps, chillers, etc. Current Transducers provide alarms for each motor so the owner

is warned immediately of any abnormal operating condition. Low pump flows will be alarmed

if the strainer is dirty or the coupling is broken. Low fan flows will be alarmed if filters are

dirty, belts are slipping, or dampers (fire, smoke, etc.) are closed. High motor loads will alarm

if bearings are dry or worn, or belts are out of alignment.

Mounting CT's CT's are generally located in the main breaker panel or in branch distribution panels

where space is always at a premium. Since CT's do not have to be installed 90 degrees to

the conductor run (the conductors can go through the CT at any angle) they are generally

held in place with plastic tie wraps. CT's with mounting feet are available if appearance is

important and there is enough room to accommodate this type of mounting arrangement.

Installing CT's Window type CT's should be mounted with the H1 side of the

window towards the power source. The X1 secondary

terminal is the polarity terminal (Figure 3).The polarity marks

of a current transformer indicate that when a primary current

enters at the polarity mark (H1) of the primary, a current in

phase with the primary current and proportional to it in

magnitude will leave the polarity terminal of the secondary

(X1).

If a CT test switch is used, the switch must have a "make-before-break" contact pattern to

assure that the CT is not open-circuited during transition.

Normally CT's should not be installed on "Hot" services. The power should be

disconnected when the CT's are installed. Many times this is not possible because of

critical loads such as computers, laboratories, etc. that cannot be shut down. Split core

CT's should not be installed on "Hot" uninsulated bus bars under any conditions.

On existing cable installations where the monitoring point is not close to a cable end,

small ring core CT's can be shunt installed on #8 cable or smaller by using Hot Tap

insulation piercing connectors similar to those made by 3M. A parallel shunt through the

CT is connected to the power cable as shown in (Figure 4). Tape all bare ends.

Check your work before leaving the installation. Make sure all connections are tight and

the installation is neat.

CAUTION: Never open-circuit a CT secondary while the primary is energized.

High crest voltages may occur across the open secondary circuit. To avoid personal

injury or equipment damage, the secondary must always be short-circuited or

connected to a burden. NOTE: A buzzing transformer is an indication of an open

secondary.