Project Background
The customer's string PV inverter experienced over-temperature derating during full-load operation in high summer temperatures, affecting power generation. The original supplier's inductor showed lacquer film aging after long-term operation at 85°C.
Technical Challenges
- Sustained current of 60A, requiring both DC resistance and temperature rise to decrease.
- Outdoor environment, requiring validation through high-temperature, high-humidity, and thermal shock tests.
- Fixed installation space, inductor height must not exceed 40mm.
- Design life requirement of 15 years.
Our Solution
Utilizing a large cross-section magnetic core with flat copper wire winding, and optimizing the mounting and potting structure:
- Flat copper wire replaces round wire, improving fill factor and reducing DC resistance by approximately 12%.
- Selecting core material with high Curie temperature, keeping inductance attenuation within 8% at 85°C.
- Switching to Class H insulation varnish and high-temperature potting compound to enhance heat aging resistance.
- Optimizing pins and mounting structure to improve vibration resistance.
Delivered Results
- Under full-load conditions, inductor temperature rise reduced from 62°C to 48°C, no longer triggering derating.
- After 1000 hours at 85°C/85%RH, inductance change is less than 5%, with no lacquer film aging.
- Passed the customer's 15-year equivalent accelerated life test.
- Became the main supplier for this platform, with annual supply exceeding 300,000 units.