International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 3, Issue 1, January 2014
ISSN 2319 - 4847
Establishment of evaluation metric and quality
analysis of enamel coating thickness and
thermal resistivity of copper wire using arm7
processor
1
Amruta Patil and 2Prof. R. M. Khaire
1,2
Department of E&TC Engg., BVDUCOE, Pune
Abstract
Paper deals with the improvement in quality control for production of transformers and electric motor windings. Uniform coating
of enamel on the copper wire is most essential, because a scratch or abrasion on the transformer/motor winding may leads to
short circuit between the windings. Also the resistivity of the wire should be least as it is a good conductor, but the resistivity is
dependent on temperature. So, the thermal resistivity is the second parameter which has to be considered. The rejection of
transformer or motor can be avoided by monitoring uniformity of enamel coating thickness and thermal resistivity of copper wire.
In this paper, we propose implementation of abrasion and thermal resistivity test methods on the same chassis with the add-on
features of reduction in cost, size, power consumption and test time due to ARM7 processor.
Keywords: Abrasion and thermal resistivity (A&TR), Analog to Digital Converter (ADC), Digital to Analog Converter
(DAC), Human Machine Interaction (HMI), Liquid Crystal Display (LCD)
1. INTRODUCTION
Enameled copper wires are used as windings in the transformer or motor manufacturing. So the physical properties of
copper wire should be verified against the standard specifications provided by manufactures. If the scratch or abrasion is
present on the enamel coating then it may cause short circuit in the windings. Also if the resistance increases rapidly with
the temperature then the conductivity of the wire decreases which might be lead in heavy voltage drop across windings
which will further cause a huge damage. The Transformer/motor gets rejected in its primary stage, called as infant
mortality.[1] The “Abrasion and thermal resistivity tester” (A&TR Tester) proposed in paper, will continuously monitor
the enamel coating thickness to ensure the uniformity and thermal resistivity threshold. Use of this device will result in
reduction of product rejection rate. Faster testing increases rate of production. It will also result in overall improvement in
efficiency and reduction in energy consumption.
The “Abrasion and thermal resistivity tester” will improve the production cycle in manufacturing of motors &
transformers. The A&TR Tester which is proposed here is a keen quality conscious, automated and based on modern
technology as compared to the latest equipment available in the market. In the market two separate equipments are
available to check the enamel thickness and thermal resistivity of the copper windings. Here these two features are
clubbed together. This equipment is the user friendly device and safe as a human machine interaction (HMI) type. The
prominent application of the proposed tester is it will be a good addition to input quality control department for the
transformer and motor manufactures.
2. COMPARISON OF CURRENT MARKET PRODUCT AND PROPOSED SOLUTION
Currently in the market two separate equipments are available to check the uniformity of enamel thickness and thermal
resistivity of the copper windings. These traditional equipments are weighted, human operating & costlier. The man
made errors, environmental errors, and precision errors are also involved in measurements of those devices. As the
mechanical assembly involved in these traditional devices, the various losses due to friction and structure of the devices
have to include in the estimation with the delays caused by inertia. In this tester abrasion monitoring and thermal
resistivity measurement, these two features are combined together with the reduction in the requirement of area, power
consumption and cost. The A&TR Tester proposed in this project work will based on modern technology, it will automate
the measurement and have better quality control. This equipment is the safe user friendly device as compared to
traditional one.
3. VARIOUS CLASSICAL METHODOLOGIES FOR COPPER WIRE TESTING
3.1 Quality testing of enamel covering with the help of fault counter
Volume 3, Issue 1, January 2014
Page 10
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 3, Issue 1, January 2014
ISSN 2319 - 4847
Figure 1 Arrangement for enamel testing
For this test methodology we have to take 40-50m long Cu wire, then draw the test specimen through 20mm long felt
pads soaked with 3% normal Na2So4 solution without changing the direction. Rate of travel of the wire through the pads
should be about 0.25 m/sec. The fault counter must indicate defect upto resistance of 10000 Ω max. The fault counter
must indicate defect impulse, each of 0.04 sec duration at the rate of 10 impulses per sec. Continuous faults are shown by
indicator lamp. Number of faults as indicated by counter shall be reported as total no. of faults per 50m wire length.[2,3]
3.2 Copper wire resistivity dependence on temperature
The resistance of conductor depends on temperature. So, the following formula gives relation between resistance and
temperature and corresponding notations and their abbreviations.
Copper and Aluminum have the standard α value = 0.004041 and 0.004308 per degree Celsius respectively at 20̊
Celsius.[4]
4. WHY TO USE ARM 7 PROCESSOR?
4.1 Various Tasks performed by processor within the proposed system
For the sake of automation, storage, processing and monitoring of the measured data the controller has to include as a
core of this tester. For the proposed device the selected controller is ARM 7.It will generate initialization signal input for
voltage/current source and collect response of voltage/current sensor.
4.2 In-built Features of processor
ARM7 is 16-bit/32-bit controller with real-time emulation that combines the microcontroller with up to 512 kB of
embedded high-speed flash memory. A 128-bit wide memory interface and unique accelerator architecture enable 32-bit
code execution at the maximum clock rate. The ARM7 LPC2364/65/66/67/68 is ideal for multi-purpose serial
communication applications. They incorporate a 10/100 Ethernet Media Access Controller (MAC), USB full speed device
with 4 kB of endpoint RAM (LPC2364/66/68 only), four UARTs, two CAN channels (LPC2364/66/68 only), an SPI
interface, two Synchronous Serial Ports (SSP), three I2C-bus interfaces, and an I2S-bus interface. This blend of serial
communications interfaces combined with an on-chip 4 MHz internal oscillator, SRAM of up to 32 kB, 16 kB SRAM for
Ethernet, 8 kB SRAM for USB and general purpose use, together with 2 kB battery powered SRAM make these devices
Volume 3, Issue 1, January 2014
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 3, Issue 1, January 2014
ISSN 2319 - 4847
very well suited for communication gateways and protocol converters. Various 32-bit timers, an improved 10-bit ADC,
10-bit DAC, one PWM unit, a CAN control unit (LPC2364/66/68 only), and up to 70 fast GPIO lines with up to 12 edge
or level sensitive external interrupt pins make these microcontrollers particularly suitable for industrial control and
medical systems.[5]
5. ARCHITECTURE OF ABRASION AND THERMAL RESISTIVITY TESTER
Figure 3 Block schematic of Abrasion and thermal resistivity tester
Major Units of the block diagram are explained
5.1 Power Supply- Power supply is the unit which supplies required power to the different block circuits for performing
their assigned tasks. So, for the accurate output the supply must be regulated and protected against variation in output
due to environmental changes. Again for the power supply we have to consider following things(1)Transformer
design:-This is basically to convert the single phase, 230V, 50Hz AC supply to required DC supply.(2)Buck
converter:- It is a DC step-down converter which generates various DC values such as 5v,8v,12v,15v required for
each block in the specified block diagram.(3)Switch:- This is to connect the DC tapping’s to the various circuits of
the block diagram.
5.2 Microcontroller- As specified in III Why to use Microcontroller.
5.3 Analog Output/Input- 1.Analog output: - This block contains (1) Digital to analog converter (DAC):- The DAC is
to convert the digital data of the controller into analog data, which will further act as input to voltage or current
source. (2) Voltage or current source: - It is the practical voltage or current source which will produce the required
amount of voltage or current. This voltage or current will be then applied to the copper wire under test.2.Analog
input:-This block contains(1)Voltage or current sensor:- This sensor sense the voltage or current at the other terminal
of the copper wire.(2)Amplifier and its signal conditioning:- The amplifier and its signal conditioning block together
will amplify and modulate the sensor output to a level that can be accepted by the ADC.(3)Analog to digital converter
(ADC):- It is to convert amplifier output in digital domain for further storage and processing.
5.4 Copper wire, Mounting Assembly- Enameled wire is often used in magnets, speakers, and electric motors. In place of
a plastic or rubber coating, this wire is simply painted with a protective coating that often doubles as a flux coating.
This eliminates the need to strip the wire free of the coating before soldering it. The type of enamel, as well as its
thickness, is used to designate the grade of one, two, or three, with three being the highest grade of insulating
properties. Copper and aluminum wires can both be enameled, as can round and rectangular wire that is often used in
motor winding in order to make the most of the limited space. The following table shows typical parameters values of
Cu wire. Mounting assembly should be a wooden plate of 15cm with two rotary switches for copper wire fixing, so
that the wire can be moved 180 degree after each test to cover the whole circumference.
Table 1: Typical parameter values of Cu wire
Sr.
No.
1
2
3
Volume 3, Issue 1, January 2014
Typical Values of Cu
Characteristics
Unit
[Ohm*mm²/
Resistivity
m]
Thermal coefficient of
[1E-6/K]
resistance
Conductivity
[S*m/mm²]
Value
0.0171
39004000
58.5
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 3, Issue 1, January 2014
ISSN 2319 - 4847
6. Liquid Crystal Display (LCD) - This is to display the condition of copper wire under test
7. System flow diagram:
8. CONCLUSION
The quality of copper wire used in transformer/motor windings depends upon continuous monitoring of enamel coating
thickness and thermal resistivity of wire. The enamel thickness is in millimeter so we need a precise voltage/current
source and sensor. As it is a real time problem, ARM7 processor has been used as a decision device. It has inbuilt 10 bit
ADC-DAC card which saves on processing time. With the help of switch abrasion and thermal resistivity monitoring has
to be performed on the same chassis /board.
9. ACKNOWLEDGEMENTS
Much of the data in this paper is based on literature review of my M.Tech project. Thus I would like to acknowledge
Project guide Prof. R. M. Khaire and Industrial guide Mr. S. S. Kulkarni for their active valuable support and guidance.
References
Journal Papers:
[1] Landinger, C.; Cronin, L.D., "Fault tests on embedded copper wire and copper tape shielded single conductor
cables," Power Apparatus and Systems, IEEE Transactions on ,
vol.94, no.3, pp.959,966, May 1975
doi: 10.1109/T-PAS.1975.31929
[2] Pops, H.; Walker, J., "Origins of high voltage continuity failures in enamel coated copper magnet wire," Electrical
Electronics Insulation Conference and Electrical Manufacturing & Coil Winding Conference, 1993. Proceedings.,
Chicago '93 EEIC/ICWA Exposition , vol., no., pp.457,484, 4-7 Oct 1993
doi: 10.1109/EEIC.1993.631223
[3] Binhai Zhang; Kaiyou Qian; Wang, T.; Yuqi Cong; Zhao, M.; Xiangquan Fan; Jiaji Wang, "Behaviors of palladium
in palladium coated copper wire bonding pr ocess," Electronic Packaging Technology & High Density Packaging,
2009.
ICEPT-HDP
'09.
International
Conferenceon,vol.,no.,pp.662,665,10-13Aug.2009
doi: 10.1109/ICEPT.2009.52706683.
[4] Jaritz, M.; Biela, J., "Analytical model for the thermal resistance of windings consisting of solid or litz wire," Power
Electronics and Applications (EPE), 2013 15th European Conference on , vol., no., pp.1,10,2-6Sept.2013
doi: 10.1109/EPE.2013.
[5] Datasheet of LPC2364/65/66/67/68 (ARM) processor
Volume 3, Issue 1, January 2014
Page 13
International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 3, Issue 1, January 2014
ISSN 2319 - 4847
AUTHOR
Amruta Patil received her BE degree in electronics and telecommunication from Cummins College of Engineering for
women’s, Pune; in 2009and she is perceiving her M.TECH. Degree in Electronics and VLSI technology from Bharati
Vidyapeeth College of Engineering, Pune; under the guidance of Prof. R. M. Khaire. She has been teaching since 2010
and is currently an assistant professor in the Department of Electronics and Telecommunication at Bharati Vidyapeeth
College of Engineering, Pune. Her research interests are Embedded system applications.
Prof. R. M. Khaire is working as a Head of the Department in E&TC engg. , at Bharati Vidyapeeth College of
Engineering, Pune. He has completed his M.Tech from IIT Chennai. He is retired Brigadier from Indian Army.
Volume 3, Issue 1, January 2014
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