JIS Magnet Wire Standards I. JIS Standard Overview
1.1 Legal Status of JIS Standards
JIS standards are reviewed by the Japanese Industrial Standards Committee (JISC) and administered by the Ministry of Economy, Trade and Industry (METI). JIS standards are voluntary national standards, but they are mandatory in government procurement and specific industries (such as electricity, railway, and medical).
For the enameled wire industry, JIS C 3202, JIS C 3210, JIS C 3211 and other standards are widely adopted by major Japanese motor, home appliance, and transformer manufacturers.
1.2 JIS
Standard Revision Mechanism
The revision cycle of JIS standards is usually 5 to 7 years. Each revision will refer to the latest changes in IEC international standards to ensure the coordination between JIS and IEC.
In the past 10 years, JIS magnet wire standards have undergone 2 major revisions: the 2010 edition (introducing Grade 3 enamel level) and the 2018 edition (introducing 200°C enamel level, Class N enamel).
1.3 Internationalization of JIS Standards
JIS standards are an important reference for the International Electrotechnical Commission (IEC). JIS C 3202 is identically adopted from IEC 60317 — most technical requirements are consistent with international standards.
However, JIS retains special Japanese requirements in the following aspects: identification methods (color, enamel code), testing details (sample quantity, determination rules), packaging specifications (reel size, marking position).
II. Core JIS Magnet Wire Standards
2.1 JIS C 3202: Enameled Round
Copper Wire
JIS C 3202 is the most core Japanese enameled round copper wire standard, specifying the technical requirements for enameled round copper wire with diameters from 0.025 mm to 5.0 mm.
Main technical contents include: conductor diameter tolerance, enamel thickness grade (Grade 0/1/2/3), breakdown voltage, conductor elongation, thermal class (Class E/B/F/H/N), solderability, solvent resistance.
JIS C 3202 is identically adopted from IEC 60317-0-1, IEC 60317-1 (solderable polyurethane), IEC 60317-2 (polyester), IEC 60317-3 (polyurethane) and other series standards.
2.2 JIS C 3210: Enameled Flat
Copper Wire
JIS C 3210 specifies the technical requirements for enameled flat copper wire (rectangular copper wire).
Main technical contents include: conductor dimensions (thickness 0.80 to 5.60 mm, width 2.00 to 16.0 mm), enamel thickness (Grade 1/2/3), breakdown voltage (4,200 V minimum), thermal class (Class F/H/N), conductor resistance (≤ 0.01724 Ω·mm²/m @ 20°C).
JIS C 3210 is identically adopted from IEC 60317-0-2, IEC 60317-27 (polyesterimide), IEC 60317-29 (polyamide-imide) and other series standards.
2.3 JIS C 3211: Heat-Resistant Enameled Wire
JIS C 3211 is a Japan-specific heat-resistant enameled wire standard, covering Class H (180°C) and Class N (200°C) enamel.
Main technical contents include: conductor diameter 0.10 to 3.15 mm, enamel grade (Grade 1/2/3), breakdown voltage (3,000 V minimum), Class H 180°C, Class N 200°C, long-term thermal aging test (20,000 hours).
JIS C 3211 is not completely identical in international standards — it represents Japan’s technical leadership in the field of high-temperature enameled wire.
2.4 JIS C 3212 to C 3224 Series
The JIS magnet wire standard series also includes multiple specialized standards:
JIS C 3214: Self-bonding enameled wire (bondable magnet wire).
JIS C 3215: Served enameled wire.
JIS C 3220: Continuously transposed conductor (CTC).
JIS C 3221: Paper-covered enameled copper flat wire.
JIS C 3222: Glass-fiber covered enameled wire.
JIS C 3223: Film-wrapped wire.
III. JIS Enamel Grades
3.1 Enamel Thickness Grades
JIS C 3202 specifies 4 enamel thickness grades:
Grade 0 (thin film): minimum enamel increase, lowest breakdown voltage.
Grade 1 (standard): general grade.
Grade 2 (thick film): high breakdown voltage.
Grade 3 (extra thick): highest breakdown voltage (≥ 6,000 V).
Grade 3 is mainly used for windings of high-voltage motors, high-frequency transformers, and high power density motors.
3.2 Breakdown Voltage Requirements
The following table summarizes the breakdown voltage requirements of JIS C 3202 under different enamel grades (1.0 mm diameter enameled round copper wire):
| Enamel Grade | Breakdown Voltage (Minimum) | Breakdown Voltage (Typical) |
|---|---|---|
| Grade 0 | 1,500 V | 2,000 V |
| Grade 1 | 2,800 V | 3,500 V |
| Grade 2 | 4,200 V | 5,000 V |
| Grade 3 | 6,000 V | 7,500 V |
Grade 2 is the mainstream choice for motor windings, and Grade 3 is the mainstream choice for high-voltage motors and transformers.
3.3 Thermal Class
JIS C 3202 and JIS C 3211 specify 5 thermal classes:
Class E (120°C): polyurethane, polyesterimide.
Class B (130°C): polyurethane, polyesterimide.
Class F (155°C): polyesterimide, modified polyester.
Class H (180°C): polyamide-imide, polyimide.
Class N (200°C): polyamide-imide 200, polyimide 200.
Class N is the highest thermal class specific to Japan — corresponding to 220°C in international standards (IEC), but defined as 200°C in JIS.
IV. JIS Comparison with Other Standards
4.1 JIS and IEC Comparison
JIS and IEC maintain a high degree of consistency in the field of enameled wire. JIS C 3202 is identically adopted from IEC 60317 series — most technical parameters can be directly compared.
Main differences include: identification methods (JIS uses Japanese codes, IEC uses English codes), testing details (JIS specifies stricter sample quantity), packaging specifications (JIS uses Japanese standard reels).
4.2 JIS and NEMA Comparison
NEMA MW 1000 is the American motor winding wire standard. JIS and NEMA differ in the following aspects:
Conductor resistance: JIS 0.01724 Ω·mm²/m vs NEMA 0.017241 Ω·mm²/m (basically consistent).
Breakdown voltage: JIS Grade 3 ≥ 6,000 V vs NEMA Heavy ≥ 5,800 V (JIS slightly higher).
Thermal class: JIS Class N 200°C vs NEMA 220°C (different).
4.3 JIS and GB Comparison
Chinese national standard GB/T 6109 is identically adopted from IEC 60317. JIS and GB are basically consistent in technical parameters — the main differences are in identification methods and testing details.
For Chinese enameled wire enterprises exporting to Japan, focus should be on: Japanese identification (color codes, enamel codes), Japanese packaging (reel size, marking position), Japanese customer special requirements (such as JIS C 3003 test methods).
4.4 Main Standards Comparison Table
The following table summarizes the core standard comparison of JIS, IEC, NEMA, and GB in the field of enameled round copper wire:
| Standard System | Core Standard Number | Main Content |
|---|---|---|
| JIS (Japan) | JIS C 3202 | enameled round copper wire general technical |
| JIS (Japan) | JIS C 3210 | enameled flat copper wire |
| JIS (Japan) | JIS C 3211 | heat-resistant enameled wire (Class H/N) |
| IEC (International) | IEC 60317 | enameled wire series standards |
| NEMA (United States) | MW 1000 | comprehensive enameled wire standard |
| GB (China) | GB/T 6109 | enameled round copper wire |
| Standard System | Core Standard Number | Main Content |
|—|—|—|
| JIS (Japan) | JIS C 3202 | enameled round copper wire general technical |
| JIS (Japan) | JIS C 3210 | enameled flat copper wire |
| JIS (Japan) | JIS C 3211 | heat-resistant enameled wire (Class H/N) |
| IEC (International) | IEC 60317 | enameled wire series standards |
| NEMA (United States) | MW 1000 | comprehensive enameled wire standard |
| GB (China) | GB/T 6109 | enameled round copper wire |
V. Test Methods
5.1 Breakdown Voltage Test
The breakdown voltage test method specified in JIS C 3202 is the same as IEC 60851: using the metal ball electrode method or metal foil electrode method, gradually increasing the voltage until the enamel breaks down.
Sample quantity: 5 samples are randomly selected for each specification.
Determination rule: the minimum breakdown voltage of the 5 samples must be ≥ standard requirement.
5.2 Conductor Elongation Test
The elongation test method specified in JIS C 3202: stretch the enameled wire to fracture on a tensile testing machine and measure the elongation at fracture.
Sample quantity: 3 samples are randomly selected for each specification.
Determination rule: the average value of the 3 samples must be ≥ standard requirement.
5.3 Heat Shock Test
The heat shock test specified in JIS C 3202: stretch the enameled wire at 20 percent elongation under 200°C conditions to check whether the enamel cracks.
Sample quantity: 5 samples are randomly selected for each specification.
Determination rule: all 5 samples must not crack to be qualified.
5.4 Long-Term Thermal Aging Test
The long-term thermal aging test specified in JIS C 3211: place the enameled wire at different temperatures for 20,000 hours and periodically detect the breakdown voltage.
Determination rule: extrapolate the maximum working temperature corresponding to 20,000 hours life according to the Arrhenius equation.
VI. Certification and Procurement
6.1 JIS Certification
JIS certification is divided into two categories: JIS Mark Certification (product certification) and JIS Factory Certification (system certification).
JIS Mark Certification is implemented by certification bodies authorized by the Ministry of Economy, Trade and Industry (such as JQA, JET). Certification cycle is 3 to 6 months.
JIS Factory Certification: the factory passes ISO 9001 + JIS factory audit.
6.2 Certification Costs
JIS Mark Certification costs include: application fee (approximately 500,000 yen), testing fee (approximately 1 to 3 million yen), certificate fee (approximately 100,000 yen per year).
For suppliers with smaller annual export volumes, consider commissioning third-party agencies for JIS equivalence testing — the cost is 30 to 50 percent lower than formal certification.
6.3 Cooperation Model with Japanese Customers
Japanese customers (such as Toyota, Hitachi, Panasonic, Toshiba) requirements for enameled wire suppliers: JIS standard compliance certification, long-term supply stability, strict batch traceability, detailed factory inspection reports.
Key to gaining Japanese customer recognition: stable product quality + complete batch traceability + detailed inspection reports + timely after-sales service.
6.4 Common Issues
Common issues exporting to Japan: identification issues (no Japanese identification or identification errors), packaging issues (reel size not meeting Japanese standards), testing issues (not re-tested according to JIS methods), certificate issues (no JIS compliance certificate provided).
## VII. Conclusion
JIS magnet wire standards are the basic standards of the Japanese market, highly consistent with IEC 60317, while retaining Japanese special requirements (identification, packaging, Class N 200°C).
Core points of JIS standards: Grade 0 to 3 enamel grades (Grade 3 ≥ 6,000 V), Class E to N thermal classes (Class N 200°C), identical adoption from IEC 60317, highly comparable with NEMA/GB.
For export enterprises, JIS standard compliance is a necessary condition for entering the Japanese market. It is recommended to prioritize obtaining JIS Mark Certification — this is the certification most recognized by Japanese customers.
For procurement, when selecting Japanese enameled wire suppliers, confirm their JIS Mark Certification certificate, batch traceability system, and factory inspection report — these three points determine product quality stability.
For engineers, understanding the comparison relationship between JIS and IEC/NEMA/GB allows flexible selection of standards that meet multi-market requirements in international projects — this is a key capability of global supply chain management.
Future trends: JIS standards will continue to converge with IEC, but Class N 200°C, JIS C 3211 and other Japan-specific standards will maintain independence. The development of AI, IoT, and new energy vehicles will drive JIS to further innovate in the field of high-frequency, above 200°C enamel.