Film Capacitor Selection Guide
Film capacitors offer excellent reliability, low losses, and self-healing properties for industrial and power electronics applications.
Dielectric Types
HJC offers two main dielectric types:
- Polyester (PET) - Higher capacitance density, lower cost, good for general purpose. Tan δ ~0.5%.
- Polypropylene (PP) - Lower losses (tan δ ~0.01%), better for high-frequency. More stable over time.
Self-Healing
Metallized film capacitors self-heal when dielectric breakdown occurs. The metallization vaporizes around the fault, isolating the defect. This provides:
- Graceful degradation rather than catastrophic failure
- Tolerance of occasional voltage transients
- Extended lifetime compared to non-healing types
Voltage Derating
Recommended derating for long life:
- DC applications: 70-80% of rated voltage
- AC applications: 50-60% of rated DC voltage
- Pulse applications: Peak voltage should not exceed rated DC voltage
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Frequently Asked Questions
1. What is self-healing in film capacitors?
Self-healing occurs when a localized dielectric breakdown causes the metallized electrode to vaporize around the fault point, isolating the defect. This happens in microseconds and removes only micrograms of material. Benefits include extended lifetime, graceful degradation, and tolerance of voltage transients. Typical capacitance loss is <5% over 100,000 hours.
2. When should I use polyester vs polypropylene?
Use polyester (PET) for cost-sensitive general applications, LED drivers, and coupling circuits where higher losses are acceptable. Use polypropylene (PP) for high-frequency switching (>10kHz), resonant circuits, and precision applications where low loss is critical. Polypropylene has 10x lower dissipation factor but costs 20-30% more.
3. What is the minimum order quantity for HJC capacitors?
Minimum order quantities (MOQ) vary by product type: MLCCs typically 10,000-100,000 pieces depending on case size, Aluminum electrolytics 1,000-10,000 pieces, Film capacitors 500-5,000 pieces, Supercapacitors 100-1,000 pieces. As an authorized distributor, we stock common parts for immediate delivery and can support smaller quantities. For high-volume production, contact our sales team for pricing and scheduling.
4. Where can I get samples of HJC capacitors?
Samples of HJC capacitors are available through our authorized distributor network. You can request samples by contacting our sales team or through our website. Sample kits are available for each product family including MLCCs, electrolytics, film capacitors, and supercapacitors. Typical sample delivery time is 1-2 weeks depending on location and part availability.
5. Does HJC provide Spice models for simulation?
Yes, HJC provides Spice models for many of our capacitor products. These models include equivalent series resistance (ESR), equivalent series inductance (ESL), and capacitance values across frequency and temperature. Models are available for MLCCs, aluminum electrolytics, and film capacitors. Contact hjc's technical support team for application-specific design guidance and recommendations.