INDUSTRY COMPONENT

Primary Capacitor

Primary capacitor in AC-DC converters for energy storage and filtering

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Component Specifications

Definition
A primary capacitor is a critical passive electronic component in AC-DC converter circuits that stores electrical energy in an electric field, primarily used for smoothing rectified AC voltage, filtering high-frequency noise, and providing temporary power during load transients. It functions as the main energy reservoir between the rectifier stage and the regulator/load, ensuring stable DC output by reducing ripple voltage and improving power quality.
Working Principle
Operates on electrostatic energy storage principles where charge accumulates on conductive plates separated by a dielectric material. In AC-DC converters, it charges during AC voltage peaks and discharges during troughs, maintaining a more constant DC voltage. The capacitor's reactance decreases with frequency, effectively shunting high-frequency AC components to ground while allowing DC to pass.
Materials
Typically constructed with aluminum electrolytic materials (aluminum foil electrodes, electrolyte, paper separator) for high capacitance values (100μF-10000μF) and voltage ratings (200V-600V). Alternative materials include film capacitors (polypropylene/polyester) for high-frequency applications or ceramic capacitors for small-signal filtering.
Technical Parameters
  • ESR 10mΩ-100mΩ
  • Lifetime 2000-10000 hours at rated temperature
  • Capacitance 100μF-4700μF
  • Ripple Current 1A-20A RMS
  • Voltage Rating 200V-600V DC
  • Temperature Range -40°C to +105°C
Standards
IEC 60384, MIL-PRF-39018, JIS C 5101

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Primary Capacitor.

primary capacitor AC-DC converter capacitor electrolytic capacitor power supply capacitor smoothing capacitor filter capacitor electrical components Primary Capacitor in Electrical Equipment Manufacturing

Parent Products

This component is used in the following industrial products

AC-DC Converter

An electronic device that converts alternating current (AC) to direct current (DC).

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Engineering Analysis

Risks & Mitigation
  • Overheating from high ripple current
  • Voltage overstress causing dielectric breakdown
  • Electrolyte leakage contaminating circuits
  • Reduced lifespan at high temperatures
  • Inrush current surges during startup
FMEA Triads
Trigger: High operating temperature exceeding rated limits
Failure: Electrolyte evaporation leading to capacitance loss and increased ESR
Mitigation: Implement thermal management (heatsinks, ventilation), derate voltage/temperature specifications, use high-temperature rated capacitors
Trigger: Voltage spikes from switching transients or lightning surges
Failure: Dielectric breakdown causing short circuit or catastrophic failure
Mitigation: Add surge protection devices (MOVs, TVS diodes), use capacitors with higher voltage ratings, implement snubber circuits
Trigger: Excessive ripple current beyond component rating
Failure: Internal heating leading to thermal runaway and premature failure
Mitigation: Parallel multiple capacitors to share current, select capacitors with higher ripple current ratings, improve circuit design to reduce ripple

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
Capacitance: ±20% typical for electrolytic, ±10% for film; ESR: +50%/-30% of rated value
Test Method
IEC 60384-1 for electrical parameters, MIL-STD-202 for environmental testing, IPC-A-610 for soldering and mounting inspection

Procurement Evaluation Criteria

Not customer reviews or live demand data. These dimensions support RFQ preparation and supplier evaluation.

Technical documentation
4/5
Manufacturing capability
4/5
Inspection readiness
5/5
Supplier transparency
3/5

These scores are example evaluation dimensions, not real customer ratings, country-specific buyer feedback, or live inquiry activity.

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Frequently Asked Questions

What is the main function of a primary capacitor in AC-DC converters?

The primary capacitor stores electrical energy to smooth the rectified AC voltage, reduce ripple, filter high-frequency noise, and provide temporary power during load changes, ensuring stable DC output.

How do I select the right primary capacitor for my AC-DC converter?

Consider capacitance value (based on load current and ripple requirements), voltage rating (at least 1.5 times peak input voltage), ESR (for efficiency and heating), ripple current rating, temperature range, and physical size constraints.

What are common failure modes of primary capacitors?

Electrolyte drying (reduced capacitance), increased ESR (overheating), dielectric breakdown (short circuit), venting/leakage from overpressure, and lead corrosion from environmental factors.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

Data Basis

CNFX manufacturer profiles, technical classification, publicly available product information, and ongoing plausibility checks.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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