1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA MW 750-2009 (R2015)Dynamic Coefficient ofFriction of Film-InsulatedMagnet WireNEMA MW 750-2009 (R2014) Dynamic Coefficient of Friction of Film-Insulated Magnet Wire Published by National Electrical Manufacturers Association
2、1300 North 17th Street, Suite 900 Rosslyn, VA 22209 www.nema.org 2014 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and
3、the International and Pan American copyright conventions. NOTICE AND DISCLAIMER The information in this publication was considered technically sound by a consensus among persons engaged in its development at the time it was approved. Consensus does not necessarily mean there was unanimous agreement
4、among every person participating in the development process. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document herein is one, are developed through a voluntary standards development process. This process brings together volunteers an
5、d/or seeks out the views of persons who have an interest in the topic covered by this publication. Although NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the documents, nor does it independently test, evaluate, or verify the
6、 accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature, whether special, indirect, consequential, or compensatory, directly or ind
7、irectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this do
8、cument will fulfill any particular purpose(s) or need(s). NEMA does not undertake to guarantee the performance of any individual manufacturers or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render prof
9、essional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional
10、 in determining the exercise of reasonable care in any given circumstance. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no
11、 power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health- or safety-related informati
12、on in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. MW 750-2009 (R2014) Page 1 2014 National Electrical Manufacturers Association CONTENTS Page Foreword . 2 Introduction 3 History . 3 Section 1 GENERAL . 5 1.1 Scope 5 1.2
13、 Definition of Friction 5 1.3 Equipment Description 5 1.4 Discussion . 5 1.5 References 6 Section 2 DYNAMIC COEFFICIENT OF FRICTION TEST METHOD 7 2.1 Definitions of Terms 7 2.2 Summary of method 7 2.3 Significance . 7 2.4 Safety Statements . 7 2.5 Apparatus 7 2.6 Test Specimen 10 2.7 Procedure 10 2.
14、8 Calculation . 11 2.9 Report 11 Tables 1 Load Block Weights for Dynamic Coefficient of Friction Testing . 7 Figures 1 Diagram of a Typical Dynamic Coefficient of Friction Tester . 4 2 MaterialSapphire (Synthetic) 5 Photos 1 Synthetic Sapphires Mounted on Load Block . 5 2 Load Applied Perpendicular
15、to Wire Path 7 MW 750-2009 (R2014) Page 2 2014 National Electrical Manufacturers Association FOREWORD NEMA MW 750-2009 (R2014) was prepared by the NEMA Magnet Wire Technical Committee. NEMA Magnet Wire publications are periodically reviewed by the NEMA Magnet Wire Section for revisions considered ne
16、cessary to keep them current with technology changes. Proposed revisions should be submitted to: Senior Technical Director, Operations National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, VA 22209 This Standards Publication was approved by the NEMA Magnet Wire Sec
17、tion. Approval of a standard does not necessarily imply that all Section members voted affirmatively or participated in its development. At the time of approval, the Magnet Wire Section was composed of the following members: Alconex Specialty Products Fort Wayne, IN CONDUMEX Mexico City, Mexico Elek
18、trisola, Inc. Boscawen, NH Magnekn San Nicolas de los Garza, NL, Mexico MWS Wire Industries Westlake Village, CA Rea Magnet Wire Company Fort Wayne, IN Superior Essex Fort Wayne, IN This document was approved as Authorized Engineering Information on 2014. MW 750-2009 (R2014) Page 3 2014 National Ele
19、ctrical Manufacturers Association INTRODUCTION As magnet wire is transferred from its packaging to coils, the designed path takes the wire over, around, and through guides, blocks, corners, and so forth, all of which are intended to help place the wire at the designed location in the coil. The force
20、 required to pull the wire through the designed winding path, exclusive of the bending force, is that which is necessary to overcome the friction developed between the magnet wire and the various surfaces that come in contact with the wire. This force is directly related to the surface characteristi
21、cs of the film insulation, the contact surfaces, and the applied lubrication. HISTORY Various devices have been used to measure the coefficient of friction of magnet wire. Several were discussed in Paper #4 at the NEMA session of the 1971 Electrical/Electronics Insulation Conference. In 1961, Paruss
22、el described a tester to measure the coefficient of friction of film-insulated magnet wire. The design was subsequently standardized and incorporated in German Standards Institute (DIN) specifications. A tester similar to the Parussel design made by Excel Industries was later demonstrated to the NEM
23、A Magnet Wire Technical Committee. At that time, an interest was expressed in redesigning the tester to simplify the operation. In 1973, NEMA Engineering Bulletin No. 4 was developed by the NEMA Magnet Wire Section to describe the subject of coefficient of friction testing and provide a test method,
24、 including the final equipment description. Eventually, the original supplier of this equipment discontinued its interest in supplying equipment, and the Research Department at the Indiana Institute of Technology supplied a new design. In 1978, this test method was introduced for discussion at a mee
25、ting of International Electrotechnical Commission (IEC) Technical Committee 55, Winding Wires. One of the critical elements of the test procedure was the selection of the surface that would be in contact with the wire specimen. Supplying and maintaining a prescribed steel surface ground to the appli
26、cable specifications was found to be cost prohibitive. As a proposed solution, representatives from The Netherlands recommended the use of synthetic sapphire elements for the load block surface. Their experience indicated that these synthetic sapphires would provide excellent life at low cost. The e
27、lements were subsequently adopted for the test surface. Earlier versions of this equipment used a dynamometer to measure the tangential force (Fd). Since the value on the dynamometer continually varies, it was necessary for the operator to estimate the average force that occurs during the test. More
28、 precision and accuracy are required so that the gage repeatability and reproducibility can be improved for this test. The dynamometer has been replaced with a force transducer selected for this work, which is a linear variable differential transformer (LVDT). The data are collected from the pressur
29、e transducer readout by computer or microprocessor. Statistical analysis can be performed on this data set resulting in mean, min, max, and standard deviation. MW 750-2009 (R2014) Page 4 2014 National Electrical Manufacturers Association MW 750-2009 (R2014) Page 5 2014 National Electrical Manufactur
30、ers Association SECTION 1 GENERAL 1.1 SCOPE This document describes a method and the equipment used for determining the dynamic coefficient of friction of film-insulated round magnet wire of sizes 14-44 AWG. 1.2 DEFINITION OF FRICTION Friction is the resistance to motion existing when a solid object
31、 is moved tangentially over the surface of another solid object which it touches, or when an attempt is made to produce such a motion. If a normal load (L) presses two surfaces together, a tangential force may be applied up to some limiting value X, and the surfaces will still remain at rest. Slidin
32、g only starts when the tangential force exceeds the static force Fs. Almost as soon as the motion starts, the tangential force takes on a characteristic value Fd, which always acts in the direction opposite to the relative velocity of the surfaces. The value of Fs is often approximately 30 percent l
33、arger than Fd, but sometimes Fs equals Fd. The ratio Fs/L is the static coefficient of friction s, while the ration Fd/L is the dynamic coefficient of friction d. The coefficients of friction are essentially a material property of the contacting surfaces and of the contaminants and other films (such
34、 as lubricants) at their interface. The coefficients of friction are independent of the load and the contact area; the dynamic coefficient of friction is also independent of the sliding velocity. This last law does not apply when the presence of a lubricant creates viscous flow in the intermediate l
35、iquid layer. In this case, the dynamic coefficient of friction normally increases with increasing sliding velocity. 1.3 EQUIPMENT DESCRIPTION The design of typical test equipment is illustrated in FIGURE 1. FIGURE 2 contains detailed drawings of synthetic sapphires and PHOTO 1 is a photograph of the
36、 load block. The tester is supplied with a wire guiding system and a take-up, which pulls the wire over the test bed at 50 ft/min (15 m/min) as shown in PHOTO 2. The test block is aligned parallel with the test bed and the test weights are perpendicular to the wire specimen. As the wire is pulled un
37、der the test block (synthetic sapphires), the friction between the wire surface and the sapphire surface develops a longitudinal force, which is transferred to the measuring system by a shaft supported by two sets of linear ball bearings in contact with the measuring system. The force indicated by t
38、he measuring system is divided by the load on the test surface to obtain the dynamic coefficient of friction. The measuring system in FIGURE 1 shows the dynamic coefficient of friction tester with a load cell in place to measure the force. An LVDT may also be used to measure the force instead of a l
39、oad cell. The electrical output from the force measurement device is fed into a computer or into a microprocessor that collects data measurements, usually 1000 points. Statistics are performed on this data set so that proper interpretation of the results can be made. 1.4 DISCUSSION Values for the dy
40、namic coefficient of friction are characteristic of the type of lubrication and the magnet wire specimen surface. The dynamic coefficient of friction values are generally not dependent on wire size. Wire lubricated with a mineral oil typically will have a mean dynamic coefficient of friction in the
41、range of 0.09 to 0.16. Wire lubricated with a paraffin wax will typically have a mean dynamic coefficient of friction ranging from 0.03 to 0.06 and will be more consistent in value as evidenced by a lower standard MW 750-2009 (R2014) Page 6 2014 National Electrical Manufacturers Association deviatio
42、n. The mean value, maximum value, and standard deviation value can be used to evaluate the application of the lubricant to the wire and smoothness of the wire surface. The test procedure is designed to provide a measure of the lubrication and the film surface smoothness as a combined value. It is as
43、sumed that the wire will be de-reeled from its packaging with minimal contact with surfaces other than those associated with the tester and packaging. It should be noted that the natural level of dust and dirt may have an effect on the coefficient of friction. If this is suspected, one or two outer
44、layers of wire should be removed from the package and the sample retested. The condition of the test surfaces in contact with the wire is very important. They should be clean and dry at the start of each separate test. The solvent used to clean the test load surface is also important. The solvent sh
45、ould remove the various types of lubricants used and should dry without leaving a film residue. 1.5 REFERENCES Alexander, P.E., “Dynamic Coefficient of FrictionA Measure of Lubricity,“ 10th Electrical/Electronics Insulation Conference, 1971 NEMA Paper #4, E.I. Conference Paper #71C38EI-116 Meriam, J
46、.L., Mechanics, Wiley, Second Edition, p 248-253 Parussel, W., “Testing the Surface Smoothness of Magnet Wires,“ Electrotechnical Periodical, Vol. 13, no. 26, December 1961, p 692-695 Rabinowicz, E., “Friction,“ The Encyclopedia of Physics, Van Nostrand Reinhold Co., Second edition p 374-376 Sears,
47、F.W., and Zemansky, M.W., College Physics, Addison-Wesley, Second Edition, p 22-25 Weisz, R.O., Thierry, M.V., and Martin, G.C., “A Study on the Windability of Magnet Wire,“ 1st Electrical Insulation Conference, 1958 “Dynamic Coefficient of Friction Test,“ NEMA Engineering Bulletin No. 4, 1973 (Resc
48、inded) “Winding Wires, Round Copper Wires, Insulated, Test and Measuring Method,“ DIN No. 46453 German Specification, October 1966, par. 5.1.5 ASTM D 1676, “Standard Test Methods for Film-Insulated Magnet Wire,” paragraphs 2937 Ampac International, Inc. Nova 900 Sales Literature MW 750-2009 (R2014)
49、Page 7 2014 National Electrical Manufacturers Association SECTION 2 DYNAMIC COEFFICIENT OF FRICTION TEST METHOD 2.1 DEFINITIONS OF TERMS Dynamic coefficient of friction d is the ratio of the force (Fd) developed between a moving wire surface and the test block surface, to the test load (L). 2.2 SUMMARY OF METHOD The wire specimen is pulled over a test bed surface under a test load (L). A frictional force (Fd) develops between the wire surfaces and is transferred to an appropriate measuring device. The reading (Fd) in grams-force is divided by the test load
