Dielectric Materials

Oil in Celem capacitors

Celem capacitors are filled with an ample amount of impregnating oil. This oil plays a critical role in ensuring effective internal heat transfer and in displacing air residues, thereby preventing internal ionization.

• Oil traces after shipping or storage
  The appearance of oil on the external surfaces following shipping or long-term storage is normal and results from internal capillary action
• Initial oil seepage during operation
  When properly mounted and cooled, a small amount of oil may seep from the capacitor during the first few hours of operation. This is a normal effect caused by thermal expansion of the internal components
• Continuous oil leakage
  Persistent oil dripping may indicate overheating. Overheating can result from improper mounting, inadequate water cooling, or electrical overloading. It is essential to identify and correct the root cause, as the capacitor must not operate above its specified temperature limits.

Polypropylene

Most Celem capacitors use polypropylene as the dielectric material—selected for its superior electrical, thermal, and mechanical properties. This material choice ensures consistent, reliable performance across a wide range of demanding applications.

Low Dielectric Loss (tan δ)
Polypropylene offers an exceptionally low dissipation factor (tan δ < 2 × 10⁻⁴), minimizing energy losses and enabling high efficiency, especially in high-frequency and high-current systems.

Stable Capacitance Over Temperature
Celem polypropylene capacitors have a temperature coefficient of -300 ppm/°C, making the capacitance variation across the full operating temperature range practically negligible. This ensures stable reactive power delivery, even in varying thermal conditions.

High Dielectric Strength
Polypropylene provides excellent voltage withstand capability, making it suitable for high-power and high-voltage applications.

Thermal Stability
Polypropylene capacitors perform reliably across a wide temperature range without significant degradation.

Self-Healing Properties
In metallized film designs, polypropylene enables self-healing, allowing the capacitor to recover from localized dielectric breakdowns without compromising overall performance.

Non-Hygroscopic
Polypropylene does not absorb moisture, which enhances long-term reliability and makes it suitable for use in humid or harsh environments.

Excellent Insulation Resistance
Ensures low leakage current and stable dielectric performance over time.

PPS Based Capacitors for High Temperature

Celem High Temperature Capacitor Series

Mica based capacitors

For applications where operating temperatures or frequencies exceed the capabilities of polypropylene capacitors, mica capacitors offer a highly reliable and cost-effective alternative to commonly used ceramic capacitors.

Mica is a naturally occurring mineral, primarily mined in Asia. As with all natural resources, variability between batches is inherent, meaning the dielectric properties of mica may differ slightly from lot to lot. Despite this, mica remains a trusted material in high-performance capacitor design due to its exceptional electrical characteristics and environmental resilience.

Key advantages of mica dielectric capacitors include:

• Low dissipation factor
  Typically tan δ < 5 × 10⁻⁴, ensuring low dielectric loss and high efficiency.
• Temperature-independent dielectric constant
  Mica’s dielectric properties remain stable across a wide temperature range, allowing predictable behavior in dynamic environments.
• Wide operating temperature range
  Suitable for continuous operation at temperatures up to 150°C, making mica ideal for high-temperature or high-power-density designs.
• High dielectric constant (ε ≈ 8)
  This enables high capacitance values in smaller volumes, improving compactness without compromising performance.