Reliability Testing of Aluminum Magnet Wire Connections for Hermetic Motors J

Purdue University Purdue e-Pubs International Compressor Engineering Conference School of Mechanical Engineering 1974 Reliability Testing of Aluminum Magnet Wire Connections for Hermetic Motors J. L. Spears A. O. Smith Corporation Follow this and additional works at: https://docs.lib.purdue.edu/icec Spears, J. L., "Reliability Testing of Aluminum Magnet Wire Connections for Hermetic Motors" (1974). International Compressor Engineering Conference. Paper 94. https://docs.lib.purdue.edu/icec/94 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/ Herrick/Events/orderlit.html RELIABUITY TESTil!G OF ALUI1INU1'1 HAGNE'r WIRE CONNECTIONS FOR HERHETIC JJ[QTORS Jerry 1. Spears, Senior Haterials Engineer A. o. Smith Corp., Electric Motor Div., Tipp City, 0., USA 1 IN'l'Jl.ODUCTION to the aluminum wire and system compati'oili ty ·was maintained. However, alwr,inwn wire even Hhen pro The heart of the hermetic compressor is the stator. perly stripped is not easily fused together, and As "•~ith the other components sealed into the her with copper wire in the connection, disslinilar metic envirom~ent, the stator is expected to pro melting points made heat fusing impossible. Be vide years of reliable service. The motor manu sides heat fusing, other methods of connecting facturer, however, does not look at the hermetic aluminum wire combinations have been explored. stator as a unit but rather as a selected group of For instance, sample connections were made with materials and processes that will provide the end such advanced techniques as capacitor discharge user with the reliability and performance desired. welding, laser beam fusion, and compression cold One of the processes that has years of proven field fusing. However, the feasibility of these tech roliability is the internal stator connections niques for a production line were soon apparent,and Nhere copper magnet wire is employed. In the past more practical approaches Here considered, such as, feH years, however, the hermetic motor manufactur compression connectors, insulation piercing com ers have been designing and producin~ an increas pression connectors, and soldering. The balance ing nlliQber of almQinum Hound hermetic stators. of this paper will present experimental life test li.conomic considerations notHithstanding, aluminUlll ing data on connection methods incorporating in ma~net wire can offer inherent physical advantages. sulation piercing compression connectors and sol For exampl:o, there is evidence of better resis dering. kmce to long term ther:nal aging when organic in sulations are applied to aluninum wire, as com p.cl.red vii th copper. It is corn.'llon experience that 3 Tli:ST CRITERIA AND SAMPLE PREPARATION al1J.minum Hire Hinds easier once proper tensions are adj-tlsted. Springback characteristics in alumi The development of these reLtability tests did not num allow for uniform coil conformation and more come about haphazardly. It was known from pre efficient use of available space. These advantages vious test experience, with non-her.metic type partially offset the lower conductivity values of Inotors, that four inherent characteristics of alu alwninum wire. Historically, hovJever, the primary minum were detrimental to a connecting process. drawback in using almninum magnet wire has been These were: aluminum oxide formation, cold flow, associated with the'development of reliable con coefficient of thermal expansion and suscepti necting techniques. The objective of this paper is bility to corrosion when coupled with a disf.;i:::rlilar to discuss the state of the art in reliability material. Since the compressor environment mini testing of aluminm~ ma,o;net Hire connections for mizes the effects of oxygen and moisture, efforts hermetic motors. The paper will also deal with the were concentrated on evaluating connections from types of almninum wire connections available for the standpoint of cold flow and thermal expansion. the industry and a discussion of their relative l'lli th these considerations in mind, the follo<Ving Tneri ts. Comments and data resarding the long term test parameters were established: reliability of these connections will also be COV<J.r'ed. A. Envirolli'lent Saturated vapor of Refrigerant- 22, and/or R-12. Refrigeration u:rade oil. 2 IIH' ;;RlBL COlli JECTICJNS & COJJNECTING Ht;'J.'HODS J3. Test Vessels hodified compressors, compressor ~JPically, hennetic stators are random wound coils shells and stairuess steel auto of either copper or aluminUlll magnet TJJire, or in claves. some designs, windings can GrllPloy both alUlllinum and copper wire. Connections include various com c. Test a) Constant current input. binations of magnet wire to magnet wire splices or Conditions b) Thermal shock cycling. magnet wire to lead wire joints. Copper connec c) Time controlled stress tions in hermetic stators are almost always pig periods. tailed tor;,et her and then fused and braz:ed. With d) Hillivolt drop & resistance tl1e advunt of high tE'.Jnperature organic ''ire insula measurements to monitor con tions, an additional step of insulation prestrip nection deterioration. ping was added to the copper wire fuse and braze ;:Jrocess. Alwninum magnet Hire offered same new D. Test Samples a) 1'Jire combinations representa~ challenges. The sane insulation could be applied tive of actual stator con- 39 nections. All Connections Hade With Hochanical Clips b) Connection teclmiques repre senting proven methods, along ]; .s. 16 AWG aluminum magnet wire was not with large numbers of samples (3 samples) stripped. to statistically test new connection processes. c.s. 16 AWG aluminum magnet wire was (3 samples) chemically stripped. llo reduction E. Sample a) Mechanical connections pre in bare wire diameter. Preparation pared with manufacturers' prescribed tooling and pro H.S. 16 AWG alwninum magnet wire cedures. Fuse/braze con 5~6 stripped mechanically reducing nections prepared as per (3 sampl bare wire diameter 5%. established production pro cess specification. Sol~ H. s. Same as above, except bare wire dered connections were made 10% diameter reduced 10%. in accordance to solder man (3 samples) ufacturers' recon®endations. b) All samples were insulated M.s. Same as above, except ba~e wire l-Ji th heat-shrink polyester 15% diameter was reduced l5jb. film tubes. (3 samples) F. Test Criteria .Any condition, such as a radi This test was set up in a modified compressor cal change in resistance at the shell in order to introduce a hermetic envirorme,lt joint, overheating, or fluctua (R-22 & oil). The test was manually controlled ting millivolt drop readings with the follmving parameters: alerted the technician as to a possible connection failure. A. Constarttly balanced current - 30 amps. The test could be interrupted and individual connections B. Current off when slot winding temperature could be checked for deteriora reached 350° F. (Observed nonnal override of tion. 20° F.) It is important to realize from this point on that c. Cool dotm to 100° F. and repeat current on test results and recommended practices reflect on cycle. the materials and processes used by A. 0. Smith, and may not necessarily be true with other mater We found that the Lab ambient temperature had ials or Jnanufacturers. The evolution of our test some influence on the rate of rise, but typical 6.0° F. experience is described in the follm•ing test pro winding temperature rate of rise was 5.5' to grams. It is from these tests and supporting data per second. that we feel confident in the performance and re liability of the method chosen to connect aluminum Basically, we arrived at the following results wire in hermetic stators. after 1000 cycles: l. Connection temperatures ranked in order of ~ HOTORETTE TEST lowest to highest: This test was developed in order to closely simu A) 5% H.S. - lmvest operating temperature. late the conditions of an actual stator. A motor ette was wound with multiple turns of 16 A1rJG wire. B) Chemical stripped. At 15 intervals, the winding was broken and a con nection made. Each connection contained, in addi C) lO% N.s. tion to the 2 - 16 AWG aluminum wires, a 14 AWG stranded lead wire and a 20 A1"JG copper magnet lllire. D) N.s. Each of the 15 connections were thermocouple equipped. A thermocouple was also imbedded in the E) 15% H.s. - highest operating temperature. motorette slot to monitor winding temperature. The 15 connections were prepared as follows: Figure I illustrates the temperature pattern of the connections at various cycle intervals throughout the test. 40 sign foaturGs. FIG. I FIG. II .SERIES CONI!ECTIOlJS, ·300, HECHANICAL _ALUNINUM CONNECTOR I MAGNET WIRE .22._0, STRAlmED COPPER OP<. •. •. 'llliRI1ETIC . 200. LEAD 'L-II]'IE ·.. .)_ l ·-· ·- _\[___ .~·CONNECTION TEMP • ..... .." --- ' :5% BARE WIP.E \ ,------- COPPER 'DIA. REDUCTION .150 L ____ MAGNET WIRE 290 490 6_00. BOO FIG. III _(a) Test Series #1: 20,000 thermal shock cycles in R-22 THERIW. SHOCK & oil. 2 min. heating at 40 amps; cool 8 min. & · CYCLES repeat. 16 AvlG al'l.llllinum wire, total connector CJ1A " 10230. Connector Test Results 2. Hesistance and millivolt drop readings were Description ! Final MV Hax. Con- taken on retained samples and on the test sam Each Group Failures 1 Drop Read- nection ples following the 1000 cycle test. The re 20 Samples Noted ings ( Avg. ) Temperature sults of these data also confirrned the opti 9 Serration Mized condition reached with 5% inax. bare dia Alwnimllll Wire None 3.14 235° F. F.eter reduction plus mechanical clip to achieve ~re-str:i.pped a connection. 7 Serration Aluminum Wire None 3.54 240° F. Pre-stripped 5 AUTm;,TJ:C CURREIIT CYCLING TEST Soldered 65/35 Zn/Sn None 2.66 172° F.

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