Capacitor[2]

Updated: 2026-09-12

Overview

A capacitor is a fundamental electronic component that stores energy in an electric field between its conductive plates. It is characterized by its capacitance value (measured in farads, typically microfarads or picofarads) and voltage rating. Capacitors are essential in circuits for functions like filtering, decoupling, and energy storage. Common types include ceramic capacitors for high-frequency applications, electrolytic capacitors for high capacitance values, and film capacitors for stability. The specific values mentioned (6.8μF/400V, 2.2μF, 3.3μF, 10μF, 15μF) represent typical capacitance ratings used in power supplies, motor run applications, and signal processing.

Structure and Working Principle

A capacitor consists of two conductive plates separated by a dielectric material. When a voltage is applied, electric charge accumulates on the plates, creating an electric field. The capacitance depends on the plate area, distance between plates, and dielectric constant of the insulating material. For example, a 6.8μF/400V capacitor is designed to handle high voltage applications like AC motor run circuits, while smaller values like 2.2μF or 3.3μF might be used in timing or filtering circuits. Electrolytic capacitors use an oxide layer as the dielectric, enabling high capacitance in compact sizes but requiring correct polarity during installation.

Key Features

Capacitors are selected based on capacitance, voltage rating, temperature stability, and equivalent series resistance (ESR). High-voltage capacitors (e.g., 400V rating) are built with thicker dielectrics to prevent breakdown. Low-ESR capacitors are preferred for high-frequency applications to minimize energy loss. Film capacitors offer excellent stability and low dielectric absorption, making them ideal for precision timing circuits. Electrolytic capacitors provide high capacitance per volume but have limited lifespan and sensitivity to reverse voltage. Ceramic capacitors are compact and stable but may exhibit capacitance changes with voltage or temperature.

Application Areas

Capacitors are ubiquitous in electronics. The 6.8μF/400V type is commonly used in motor start/run circuits, power factor correction, and HVAC systems. Smaller values like 2.2μF or 3.3μF are found in signal coupling, filtering, and oscillator circuits. In power supplies, capacitors smooth voltage fluctuations (e.g., 10μF or 15μF in DC link applications). Audio equipment uses capacitors for crossover networks and tone control. Industrial applications include energy storage for pulsed power systems and snubber circuits to suppress voltage spikes.

Maintenance and Precautions

Capacitors require careful handling to avoid damage. Electrolytic types degrade over time and may need replacement after 5-10 years. Always discharge capacitors before handling to prevent electric shock, especially high-voltage units like 400V models. Avoid exceeding the rated voltage or temperature, as this can shorten lifespan or cause catastrophic failure. For polarized capacitors (e.g., electrolytics), observe correct polarity during installation. Store capacitors in dry conditions to prevent moisture absorption, which can alter performance.

B2B Procurement Guide

When sourcing capacitors, specify capacitance, voltage rating, tolerance, and type (e.g., 6.8μF ±10%, 400V, film capacitor). For bulk purchases, verify manufacturer certifications (e.g., UL, RoHS) and request lifetime estimates, especially for electrolytic capacitors. Consider lead time and MOQ (minimum order quantity) for specialized values like 3.3μF or 15μF. Compare pricing from multiple suppliers, as costs vary by material (e.g., tantalum vs. aluminum electrolytic). Test samples for ESR and leakage current to ensure quality before large-scale procurement.