1 Introduction
Aluminum enameled wire is the insulated winding wire that adopts pure aluminum or aluminum alloy round wire or flat wire as conductor and surface coats polyurethane, polyester, polyesterimide, polyamideimide, polyimide and other insulation varnish film, is the key raw material for small medium motor, household appliance, low voltage transformer, low voltage inductor, special application motor. Aluminum enameled wire compared with copper enameled wire has significant advantages of light weight 70%, low cost 30 to 50%, rich resources.
The reliability of aluminum enameled wire in motor is the key issue concerned by motor engineers. Based on IEC 60317, NEMA MW 1000-2018, GB/T 6109, JB/T 4074 and other standards, this article systematically describes the reliability of aluminum enameled wire in motor from seven dimensions including product system, reliability analysis, motor application, copper aluminum comparison, selection design, application attention and summary.
2 Aluminum Enameled Wire Overview and Product System
2.1 Aluminum Enameled Wire Product Classification
Aluminum enameled wire product classification covers five major categories including pure aluminum enameled wire, aluminum alloy enameled wire, copper clad aluminum enameled wire, copper clad aluminum enameled wire, aluminum enameled flat wire. Pure aluminum enameled wire adopts pure aluminum 1050, 1060, 1350 as conductor, conductivity not less than 61% IACS, density 2.70 g/cm³, conductor diameter 0.30 to 5.00 mm, heat resistance class 130 to 220 degrees Celsius. Aluminum alloy enameled wire adopts aluminum magnesium silicon 6101, aluminum magnesium 5052, aluminum silicon 4043 as conductor, conductivity 50 to 55% IACS, mechanical strength better than pure aluminum. Copper clad aluminum enameled wire adopts copper clad aluminum CCA as conductor, copper volume ratio 10% or 15%, combines copper weldability and aluminum lightweight low cost advantage. Aluminum enameled flat wire conductor width 2.00 to 12.00 mm, thickness 0.50 to 3.15 mm, suitable for flat wire motor, planar motor, NEV drive motor.
2.2 Aluminum Enameled Wire Product Technical Features
Aluminum enameled wire technical features embody six dimensions. Light weight, aluminum density 2.70 g/cm³, is about 30% of copper 8.96 g/cm³. Low cost, aluminum price far lower than copper, same current capacity aluminum enameled wire cost is about 30% to 50% of copper enameled wire. Conductivity, aluminum conductivity about 61% IACS, is 61% of copper, same resistance aluminum conductor cross sectional area is about 1.6 times of copper. Mechanical strength, pure aluminum tensile strength 70 to 110 MPa, lower than copper 200 to 280 MPa, aluminum alloy 6101 tensile strength 150 to 220 MPa. Corrosion resistance, aluminum surface naturally forms dense aluminum oxide protective layer, atmospheric corrosion resistance better than copper. Weldability, aluminum welding difficulty greater than copper, copper clad aluminum wire combines copper weldability and aluminum lightweight advantage.
2.3 Aluminum Enameled Wire Applicable Standards
Aluminum enameled wire applicable standards cover four major categories including international, national, industry, enterprise. International standards include IEC 60317-0-3 to 60317-86 series enameled wire standards, IEC 60851 enameled wire test method, IEC 60172 enameled wire thermal life evaluation, NEMA MW 1000-2018 enameled wire standard. National standards include GB/T 6109 enameled round winding wire, GB/T 7095 enameled flat winding wire, GB/T 4074 enameled wire test method. Industry standards include JB/T 4074 enameled wire test method, JB/T 5331 aluminum enameled round wire. Enterprise standards are higher than national standards to ensure product quality.
3 Aluminum Enameled Wire Reliability Technical Analysis
3.1 Aluminum Enameled Wire Electrical Reliability
Aluminum enameled wire electrical reliability covers five dimensions including conductor resistance, insulation resistance, breakdown voltage, dielectric loss, partial discharge. Conductor resistance aspect, aluminum conductor resistivity 2.65×10⁻⁸ Ω·m, is 1.58 times of copper 1.68×10⁻⁸ Ω·m, to achieve same resistance, aluminum conductor cross sectional area needs to increase to 1.58 times of copper, diameter increase to 1.26 times of copper.
Insulation resistance and breakdown voltage aspect, basically same as copper enameled wire, varnish film insulation resistance not less than 1000 MΩ, polyester varnish film breakdown not less than 1500 V, polyesterimide not less than 3000 V, polyamideimide not less than 5000 V. Dielectric loss and partial discharge aspect, tanδ not exceeds 0.005, winding partial discharge inception voltage not less than 2 times rated voltage.
3.2 Aluminum Enameled Wire Mechanical Reliability
Aluminum enameled wire mechanical reliability covers five dimensions including conductor strength, varnish film adhesion, varnish film wear resistance, winding performance, vibration resistance. Conductor strength aspect, pure aluminum 1350 tensile strength 70 to 110 MPa, elongation not less than 25%, aluminum alloy 6101 tensile strength 150 to 220 MPa, elongation not less than 15%, compared with copper 200 to 280 MPa, needs to increase cross sectional area or adopt aluminum alloy to improve.
Varnish film adhesion and wear resistance aspect, basically same as copper enameled wire, adhesion detected through sudden pull, peel, thermal shock test, wear resistance times not less than 50 times single direction friction, hardness meets NEMA MW 1000-2018 requirement. Winding performance aspect, aluminum conductor softness better than copper, but elastic modulus lower, winding easy to deform, needs to control tension. Vibration resistance aspect, aluminum conductor density low, vibration inertia small, vibration attenuation fast, vibration life similar or slightly better.
3.3 Aluminum Enameled Wire Thermal Reliability
Aluminum enameled wire thermal reliability covers five dimensions including heat resistance class, thermal aging life, thermal shock performance, thermal expansion matching, heat dissipation performance. Heat resistance class and thermal aging life aspect, same as copper enameled wire, polyurethane 130, polyester 155, polyesterimide 180, polyamideimide 220 degrees Celsius, accelerated aging 180 degrees Celsius 6000 to 10000 hours, 220 degrees Celsius 20000 to 50000 hours, varnish film aging life not affected by conductor material.
Thermal shock and thermal expansion matching aspect, varnish film thermal shock test temperature 175 to 200 degrees Celsius, no crack no bubble, aluminum conductor thermal expansion coefficient 23×10⁻⁶ /℃, slightly higher than copper 17×10⁻⁶ /℃. Heat dissipation performance aspect, aluminum specific heat 0.90 J/g·K, higher than copper 0.38 J/g·K, aluminum conductor unit mass temperature rise lower, heat dissipation slightly better.
3.4 Aluminum Enameled Wire Chemical and Joint Reliability
Aluminum enameled wire chemical reliability covers three dimensions including corrosion resistance, chemical resistance, varnish film stability. Aluminum surface naturally forms dense aluminum oxide Al₂O₃ protective layer, thickness about 2 to 10 nm, atmospheric corrosion resistance better than copper, salt spray test 96 hours interface no obvious corrosion. Aluminum is amphoteric metal, acid alkali resistance slightly lower than copper, strong acid strong alkali environment needs polyimide or polyamideimide varnish film protection.
Aluminum enameled wire joint reliability is the key challenge in motor application, is the main factor limiting wide application. Aluminum conductor surface naturally forms aluminum oxide layer, seriously affects electrical connection reliability, aluminum copper joint easy to produce galvanic corrosion, aluminum creep tendency greater than copper, long term operation aluminum joint loose, contact resistance increase, temperature rise increase, finally cause joint failure. Mechanical connection needs to adopt torque control, anti loose washer, regular inspection.
4 Aluminum Enameled Wire Application in Different Motors
4.1 Small Medium Household Appliance Motor
Small medium household appliance motor covers air conditioner compressor, refrigerator compressor, washing machine, electric fan, range hood, microwave oven, rice cooker, water heater and other household appliance motor. Air conditioner compressor motor capacity 0.5 to 5 kW, speed 1500 to 3600 rpm, efficiency not less than 85%, widely adopts aluminum enameled wire, meets household appliance motor reliability requirement. Refrigerator compressor motor capacity 0.1 to 1.5 kW, efficiency not less than 80%. Washing machine motor capacity 0.2 to 1.5 kW, efficiency not less than 80%, widely adopts aluminum enameled wire, aluminum enameled wire in household appliance motor field widely applied, market share exceeds 70%.
4.2 Small Industry and NEV Drive Motor
Small industry motor covers small three phase asynchronous, single phase asynchronous, DC, servo, stepping, permanent magnet synchronous, variable frequency motor. Small three phase asynchronous motor capacity 0.1 to 15 kW, part stator winding adopts aluminum enameled wire. Small single phase asynchronous motor capacity 0.05 to 3 kW, efficiency not less than 70%, widely adopts aluminum enameled wire. Small DC motor capacity 0.01 to 1 kW, small variable frequency motor capacity 0.05 to 5 kW, adopts aluminum enameled wire needs corona resistant varnish film.
NEV drive motor has extremely high requirement for power density, efficiency, reliability, lightweight, capacity 50 to 400 kW, speed 15000 to 25000 rpm, efficiency not less than 95%, aluminum enameled wire in NEV drive motor application still in exploration stage, currently mainstream adopts copper enameled wire or copper enameled flat wire. Aluminum enameled flat wire is research hotspot, slot fill factor high, but needs to solve aluminum conductor mechanical strength, aluminum copper joint reliability and other key technology.
4.3 Large Motor and Special Motor
Large motor capacity above 100 kW, voltage 380 V to 13.8 kV, efficiency not less than 95%, widely adopts copper enameled wire, aluminum enameled wire in large motor less applied, the reason is aluminum conductor cross sectional area large, occupy iron core slot space large, motor power density reduce. Special motor covers traction, marine, aerospace, robot, medical equipment motor, aluminum enameled wire application very few, widely adopts copper enameled wire. Transformer, inductor, reactor, filter and other small medium low voltage electromagnetic components, aluminum enameled wire application relatively wide.
5 Aluminum Enameled Wire and Copper Enameled Wire Comparison
5.1 Physical Property Comparison
Aluminum enameled wire and copper enameled wire physical property comparison covers six dimensions including density, conductivity, resistivity, tensile strength, elongation, thermal expansion coefficient. Density aspect, aluminum 2.70 g/cm³, copper 8.96 g/cm³. Conductivity aspect, aluminum 61% IACS, copper 100% IACS. Resistivity aspect, aluminum 2.65×10⁻⁸ Ω·m, copper 1.68×10⁻⁸ Ω·m, aluminum is 1.58 times of copper. Tensile strength aspect, pure aluminum 70 to 110 MPa, pure copper 200 to 280 MPa. Elongation aspect, pure aluminum 25% to 35%, pure copper 30% to 50%. Thermal expansion coefficient aspect, aluminum 23×10⁻⁶ /℃, copper 17×10⁻⁶ /℃.
5.2 Economic Comparison
Aluminum enameled wire and copper enameled wire economic comparison covers four dimensions including conductor material cost, processing cost, transportation cost, recycling cost. Conductor material cost aspect, aluminum price about 15% to 25% of copper price, same current capacity aluminum enameled wire conductor cost is about 20% to 40% of copper enameled wire. Processing, transportation, recycling aspect, aluminum density low, about 30% of copper conductor, aluminum recycle rate 95% above, copper recycle economic value higher than aluminum.
5.3 Application Scenario Comparison
Aluminum enameled wire and copper enameled wire application scenario comparison covers five dimensions. High frequency high power density motor aspect, aluminum resistivity high, copper enameled wire is first choice. Low frequency large power motor aspect, aluminum mechanical strength low, copper enameled wire is first choice. Household appliance motor aspect, aluminum enameled wire widely applied, meets household appliance requirement. NEV drive motor aspect, aluminum copper joint reliability low, copper enameled wire is mainstream. Special motor aspect, reliability requirement extremely high, widely adopts copper enameled wire.
Overall, aluminum enameled wire suitable for cost sensitive, power density requirement not high small medium motor and household appliance motor, copper enameled wire suitable for high reliability requirement large motor, NEV drive motor, special motor.
6 Aluminum Enameled Wire Selection and Design Key Points
6.1 Aluminum Enameled Wire Selection Principle
Aluminum enameled wire selection principle covers conductor specification, varnish film system, heat resistance class, insulation class, reliability requirement, application scenario, cost budget seven major principles. Conductor specification aspect, low current capacity select round conductor, medium high current capacity select rectangular conductor, round conductor diameter 0.30 to 5.00 mm, rectangular conductor width 2.00 to 12.00 mm, thickness 0.50 to 3.15 mm, aluminum conductor cross sectional area about 1.6 times of copper conductor.
Varnish film system aspect, 130 to 155 degrees Celsius select polyurethane or polyester varnish film, 180 select polyesterimide, 200 to 220 select polyamideimide, household appliance select polyurethane or polyester, small industry select polyester or polyesterimide, special application select polyamideimide.
Heat resistance class aspect, A class 105 select MW 1-C, B class 130 select MW 2-C, F class 155 select MW 5-C, H class 180 select MW 7-C, household appliance select B or F class, small industry select F class, NEV drive select H class. Reliability requirement aspect, household appliance moderate, large industry NEV special motor reliability requirement high, recommend copper enameled wire.
6.2 Aluminum Enameled Wire Winding Design
Aluminum enameled wire winding design principle same as copper enameled wire, but needs to consider aluminum conductor feature, winding type covers cylindrical, disc, layer, planar, hairpin five major types. Cylindrical suitable for low voltage, small capacity, power frequency motor, layer number 1 to 10, each layer turn number 10 to 200, aluminum conductor diameter 0.50 to 5.00 mm, layer insulation use DMD or NMN 0.2 to 1.0 mm. Disc suitable for medium high voltage, medium capacity motor, disc number 10 to 200, each disc 5 to 50 turns. Layer suitable for high frequency, low voltage, large current motor, aluminum conductor diameter 0.20 to 1.50 mm. Planar suitable for high frequency switch power magnetic component, aluminum conductor thickness 0.10 to 0.50 mm. Hairpin is NEV research hotspot, slot fill factor high, needs to solve aluminum copper joint reliability issue.
6.3 Aluminum Enameled Wire Joint Design
Aluminum enameled wire joint type covers aluminum aluminum direct joint, aluminum copper transition joint, copper clad aluminum wire replacement three ways, aluminum enameled wire joint reliability lower than copper enameled wire, must adopt special joint design. Aluminum aluminum direct joint adopts cold press, mechanical press, friction welding, flash welding, ultrasonic welding process. Aluminum copper transition joint adopts copper aluminum friction welding, copper aluminum flash welding, copper aluminum cold press, needs to adopt copper aluminum transition joint box, adopt torque wrench control press torque, adopt moisture proof anti corrosion coating protection. Copper clad aluminum wire replacement is the best solution for aluminum enameled wire joint, copper volume ratio 10% or 15%, surface copper layer thickness meets welding requirement, welding process same as copper wire.
6.4 Aluminum Enameled Wire Insulation Treatment
Aluminum enameled wire insulation treatment process basically same as copper enameled wire, adopts VPI, immersion, dip, roll four processes. VPI temperature 50 to 70 degrees Celsius, vacuum degree less than 50 Pa, pressure 0.2 to 0.5 MPa, time 8 to 24 hours, impregnant adopt epoxy, modified epoxy, polyester, unsaturated polyester, silicone, polyimide impregnating varnish. Immersion, dip, roll process suitable for small batch winding, drying curing temperature 150 to 200 degrees Celsius, time 8 to 24 hours. Detection includes appearance, size, DC resistance, insulation resistance, breakdown voltage, dielectric loss, partial discharge, temperature rise, short circuit nine categories.
7 Aluminum Enameled Wire Application Attention and Future Trend
7.1 Aluminum Enameled Wire Application Attention
Aluminum enameled wire application attention covers storage transport, winding process, assembly process, application environment, maintenance five major dimensions. Storage transport aspect, temperature 5 to 35 degrees Celsius, humidity 30% to 70%, storage period not exceed 1 year.
Winding process aspect, winding tension moderate, avoid aluminum conductor stretching. Assembly process aspect, avoid mechanical impact, lead welding adopt special aluminum welding process.
Application environment aspect, temperature not exceed rated temperature, avoid strong acid strong alkali, avoid salt spray long term erosion, household appliance, small industry, inland dry environment suitable for aluminum enameled wire, marine salt spray, strong acid strong alkali environment needs caution or select copper clad aluminum wire.
Maintenance aspect, regular inspection, regular cleaning, regular test, inspection period not exceed 1 year, cleaning period not exceed 6 months, aluminum copper joint needs regular inspection torque, tighten loose joint, monitor temperature rise change.
7.2 Aluminum Enameled Wire Future Development Trend
Aluminum enameled wire future development trend covers five directions. High conductivity aluminum alloy adopts rare earth element micro alloying, improve aluminum alloy conductivity to 63% to 65% IACS. High mechanical strength aluminum alloy adopts aluminum magnesium silicon 6101, aluminum copper 2011, aluminum zinc 7075, tensile strength 200 to 400 MPa. High temperature resistant varnish film adopts PAI, PI, PBI varnish film, heat resistance class 220 to 300 degrees Celsius. Aluminum copper composite structure adopts copper clad aluminum wire, is the important technical route for high end motor application. Aluminum enameled flat wire suitable for NEV drive, rail transit traction, industry variable frequency motor, slot fill factor high.
8 Summary
Aluminum enameled wire reliability in motor is the key issue concerned by motor engineers, electrical, mechanical, thermal, chemical reliability overall meet small medium motor, household appliance motor application requirement, aluminum enameled wire joint reliability is key factor.
Aluminum enameled wire core advantage is light weight 70%, low cost 30% to 50%, rich resources, heat dissipation performance good. Core disadvantage is conductivity 61% IACS lower than copper 100% IACS, mechanical strength lower than copper, aluminum copper joint reliability lower than copper copper joint. Aluminum enameled wire suitable for small medium household appliance motor, small industry motor, low voltage transformer, low voltage inductor, household appliance motor market share exceeds 70%. Aluminum enameled wire not suitable for large industry, NEV drive, special motor.
Aluminum enameled wire and copper enameled wire is not simple replacement relationship, is complementary relationship, motor engineer should according to motor capacity, voltage class, efficiency requirement, reliability requirement, life requirement, cost budget comprehensively select aluminum enameled wire or copper enameled wire.
With five major technical development direction, aluminum enameled wire in motor application range will further expand.
Reference standards: IEC 60317-0-3 to 60317-86 / IEC 60851 / IEC 60172 / NEMA MW 1000-2018 / GB/T 6109 / GB/T 7095 / GB/T 4074 / JB/T 4074 / JB/T 5331.
Contact Information: E-mail office@cnlpzz.com, WhatsApp 0086-19337889070, Zhengzhou LP Industry Co., Ltd.
- Email: office@cnlpzz.com
- WhatsApp: 0086-19337889070
- Company: Zhengzhou LP Industry Co., Ltd.