The revolution of invertertechnology is making a huge impact on the field of motor industry. But the “killer” brought by inverters-(corona discharge) quietly kills the ordinary enameled wire.
And out of this challenge was born a product known as the Corona Resistant Enameled Aluminum Wire.
Let‘s find out more about this “special forces” grade enameled wire.
What Is Corona Resistant Enameled Aluminum Wire?
Corona Resistant Enameled Aluminum Wire: An enameled aluminum wire, it owns special Corona performance.
Differences from Ordinary Enameled Aluminum Wire:
Enameled Aluminum Wire: Coated by just normal insulating ether. (ie, polyester, polyamide-imide)
Corona Resistant Enameled Aluminum Wire : With basic class insulating enamel with corona resistant additive or using special corona resistant insulation material
What “Corona Resistant” Means
Corona: the phenomenon of internally occurring air breakdown discharge under high voltage
Corona Resistant: Ability to withstand damage to its insulation resulting from corona discharge; due to effects of free oxidative radicals and free carbon molecules.
Why Do We Need Corona Resistant Enameled Aluminum Wire?
The Inverter Motor‘s “Killer”: Corona Discharge
The output inverter PWM waveform produce high frequency pulse voltage in the motor winding.
Specific Problems:
- Surge Voltage
The output voltage waveform produced by inverters is not a pure sine wave, rather PWM square waves. The PWM square waves produce reflections at the end of the cable resulting in an overvoltage spike. - Voltage Rise Rate (dv/dt)
The rising edge of PWM waveforms have high dv/dt, and very steep. - High-Frequency Harmonics
PWM waveforms are abundant with high frequency harmonics. In What Manner Does the Corona Discharge Harm the Enameled Wire?
When windings operate under inverter drive:
Excessive frequency pulse voltage was causes in charge accumulation on the surface of echinata.
The local concentration of charge has been reached, and localized air ionization on the surface of the enaml is occurred.
The molecules chains in the enamel are bombarded with electrons coming from the ionizing particles
Enamel molecular chains degrade / breakage of insulation performance held;
Leads ultimately to enamel breakdown and inter-tooth short circuit
Enamel Lifespan Under Inverter Conditions
| Type | Lifespan (Inverter Conditions) |
|---|---|
| Ordinary Enameled Wire | 1-2 years (or even shorter) |
| Corona Resistant Enameled Wire | 10-20 years |
Core Technology of Corona Resistant Enameled Aluminum Wire
1. Corona-Resistant Insulating Enamel
Common Additives:
- Inorganic Nanomaterials: Nano alumina, nano silica
- Organic Functional Materials: Special anti-corona organic compounds
- Metal Oxides: Zinc oxide, titanium oxide
Mechanism:
- Nano materials form “barriers” in enamel
- Block electron flow from corona discharge
- Delay molecular chain breakage
2. Multi-Layer Coating Process
| Coating Layer | Function |
|---|---|
| Primer Layer | Good adhesion with aluminum conductor |
| Middle Layer | Provides mechanical strength |
| Corona-Resistant Layer | Resists corona discharge |
| Surface Layer | Provides wear resistance and lubrication |
3. Aluminum Conductor Surface Treatment
- Pre-oxidation Treatment: Forms dense aluminum oxide layer
- Coupling Agent Treatment: Enhances enamel adhesion
- Chemical Conversion Treatment: Improves corrosion resistance
Performance Advantages of Corona Resistant Enameled Aluminum Wire
Long Lifespan
‘Corona resistant’ enameled aluminum wire has a life of 5-10 times that of normal enameled aluminum wire.
High Reliability
Resist high frequency impact due to pulsed width modulation (PWM) waveforms
Is resistant to multiple occurrences of voltage surges
Reliable operation in a difficult environment over an extended period of time;
Strong Compatibility
Can use plain enameled aluminum wire instead
Suitable for use with your currently existing winding machinery
Is compatible with existing impregnation procedures
Additional Advantages of Aluminum Conductor
Light weight: Overall motor weight is reduced.
Low cost: substantially cheaper than corona resistant copper wire
Good heat dissipation: Helps reduce running temperature
Application Scenarios
1. Inverter Air Conditioning Compressors
The most widespread application. Major brands: Daikin, Mitsubishi, Gree, Haier, etc.
2. New Energy Vehicle Drive Motors
Emerging application. Requires high power density, high-frequency PWM drive, automotive-grade reliability (IATF 16949).
3. Industrial Inverter Motors
Inverter-driven industrial motors, applications requiring frequent speed regulation, energy-saving retrofit projects.
4. Wind and Solar Power
Wind turbine inverter systems, solar inverters, energy storage system inverter equipment.
5. Rail Transit
High-speed rail traction motors, subway traction systems, urban rail transit.
6. Industrial Automation
Industrial robots, CNC machine tools, automated production lines.
Specifications and Parameters
Conductor Specifications
| Conductor Diameter (mm) | Cross-sectional Area (mm²) | Typical Application |
|---|---|---|
| 0.5-1.0 | 0.2-0.8 | Small inverter air conditioners |
| 1.0-2.0 | 0.8-3.1 | Medium inverter motors |
| 2.0-3.0 | 3.1-7.1 | Large inverter motors |
Insulation Class
| Insulation Class | Max Operating Temp | Recommended Application |
|---|---|---|
| Class F | 155°C | Entry-level inverter motors |
| Class H | 180°C | Mid-range inverter motors |
| Class 200 | 200°C | High-end/automotive-grade |
| Class C | 220°C | Extreme conditions |
Corona Resistance Grade
| Grade | Corona Resistance Life | Application Scenario |
|---|---|---|
| Standard | 100-500 hours | Ordinary inverter |
| Enhanced | 500-2000 hours | High-frequency inverter |
| Advanced | 2000-5000 hours | High-end applications |
| Ultra Advanced | >5000 hours | Extreme conditions |
How to Identify Genuine Corona Resistant Enameled Aluminum Wire?
1. Performance Indicators
- Ask for corona resistance lifespan data (hours)
- Understand test methods and test voltage
- Compare data from different suppliers
2. Insulating Enamel Composition
- Confirm use of corona-resistant additives
- Understand additive type and content
- Best to have third-party test reports
3. Third-Party Certifications
- IEC 60317 related standards
- UL certification
- Industry certifications (such as automotive-grade IATF 16949)
4. Actual Application Cases
- Understand supplier’s historical application cases
- Ask if any well-known customers use it
- Understand product performance in the field
VIII. Selection Key Points
1. Clarify Inverter Parameters
- Inverter type: PWM or other
- Output voltage rating
- Switching frequency (usually 2-20kHz)
- dv/dt and surge voltage levels
2. Evaluate Working Conditions
- Operating temperature range
- Voltage rating
- Frequency range
- Environmental factors (humidity, vibration, etc.)
3. Select Corona Resistance Grade
- General inverter motors: Standard grade
- High-frequency inverter motors: Enhanced grade
- Automotive-grade: Advanced or Ultra Advanced grade
4. Verify Supplier Capabilities
- R&D capability for corona-resistant enamel
- Enamel coating process level
- Quality control system
- After-sales service capability
IX. Usage Notes
1. Winding Process
- Control winding tension to avoid damaging corona-resistant layer
- Bend radius should comply with specifications
- Use specialized winding molds
2. Welding Process
- Enamel needs to be removed first (stripping)
- Use appropriate welding process
- Avoid thermal damage during welding
3. Impregnation Process
- Select impregnating resin compatible with corona-resistant enamel
- Vacuum impregnation provides better results
- Impregnation temperature must not exceed temperature class
4. Storage and Transportation
- Avoid direct sunlight
- Maintain dry environment
- Prevent mechanical damage
Cost Analysis
Comparison with Ordinary Enameled Aluminum Wire
| Type | Relative Price | Lifespan (Inverter Conditions) |
|---|---|---|
| Ordinary Enameled Aluminum Wire | 1.0x | 1-2 years |
| Corona Resistant Enameled Aluminum Wire | 1.5-2.0x | 10-20 years |
Although corona resistant enameled aluminum wire has higher initial price, considering lifespan extended 5-10 times, reduced maintenance and replacement costs, and lower equipment failure risk, the comprehensive cost is actually lower.
Comparison with Corona Resistant Copper Wire
- Corona resistant enameled aluminum wire price is only 30%-50% of corona resistant copper wire
- Performance is comparable or even better
- Lighter weight
FAQ
Q: Can corona resistant enameled aluminum wire completely eliminate corona?
A: It cannot completely eliminate corona, but it can significantly delay corona damage to enamel. Corona resistant enameled wire can extend lifespan from 1-2 years to 10-20 years.
Q: Do all inverter motors need corona resistant enameled wire?
A: Not necessarily. Low-frequency (e.g., <5kHz), low-voltage (e.g., <400V) inverter motors can use ordinary enameled wire. However, high-frequency, high-voltage, high-power inverter motors are recommended to use corona resistant enameled wire.
Q: Can corona resistant enameled aluminum wire be used in non-inverter environments?
A: Yes, but it’s not cost-effective. In non-inverter environments, ordinary enameled aluminum wire is sufficient.
Q: What are the certification standards for corona resistant enameled aluminum wire?
A: IEC 60317 is the international universal standard. Different countries and regions also have UL, CQC and other certifications.
Q: What is the delivery time for corona resistant enameled aluminum wire?
A: Standard specifications are usually in stock. Custom specifications (special diameters, special corona resistance grades) typically require 6-10 weeks.