A capacitor (known as a condenser) is a two-terminal electrical device capable of storing energy in an electric field. It consists of two electrical conductors spaced a distance apart. The space between conductors can be filled with a vacuum or with an insulating material called a dielectric. The ability of a capacitor to store electrical charges is called capacitance.
Capacitors store energy by separating pairs of opposite charges. The simplest design for a capacitor is a parallel plate, consisting of two metal plates spaced between them. But different types of capacitors are made in many shapes, styles, lengths, circumferences, and materials.
Types OF Capacitor
There are different types of Capacitor which are given below:
- Ceramic Capacitors
- Electrolytic Capacitors
- Super Capacitors
- Film Capacitors
- Variable Capacitors
- Power Film Capacitors
Characteristics Of Capacitor
- Nominal Capacitance
- Working Voltage
- Tolerance
- Leakage Current
- Working Temperature
- Polarization
- Equivalent Series Resistance
Nominal Capacitance
Capacitance describes the ability of a capacitor to store electrical energy for a given voltage value. This value is expressed in Farad units, which include pico-Farads(Pf), nano-Farads(nF), and micro-Farads(µF). Capacitance can be increased by increasing the effective area of the electrodes, reducing the separation between the electrodes, increasing the isolation by using a suitable dielectric with a higher permittivity, or improving dipole formation.
Working Voltage
The maximum operating voltage, DC or AC, that can be applied to the capacitor during its lifetime without causing breakdown is called Working Voltage.
Tolerance
The tolerance value of a capacitor is the extent to which the capacitance can deviate from the rated value. The tolerance dimension is expressed as plus or minus. If a capacitor with a capacitance of 50μF has a tolerance of ±10%, the capacitance will vary from 0μF to 60μF.
Leakage Current
Dielectrics used in capacitors are not perfect insulators. A small current, called leakage current, flows through the dielectric.
Working Temperature
The change in the ambient temperature of the capacitor affects the capacitance. Capacitor operating temperature is from -300 C to 1250 C
Polarization
The voltage across the capacitor must have the correct polarity, positive to positive, negative to negative, and so on.
Equivalent Series Resistance (ESR)
The equivalent series resistance (ESR) of a capacitor is defined as the AC impedance of the capacitor when operating at very high frequencies and also takes into account the dielectric strength. The DC resistance of the dielectric and the plate resistance of the capacitor are measured at a specific temperature and frequency.
ESR acts as a resistor in series with a capacitor. The ESR of a capacitor is a measure of its quality. We know that in theory, a perfect capacitor is lossless and also has zero ESR. Often this resistance (ESR) causes failures in the capacitor circuits.
Specification Of Capacitor
- Capacitance value
- Voltage rating
- Temperature coefficient
- Frequency range
- Dielectric constant
- Dielectric strength
- Power factor
Capacitance Value
The value of a capacitor is measured by its capacitance value expressed in farads, microfarads, and nanofarads.
Voltage Rating
Nominal voltage is the operating voltage of the capacitor and is measured in volts.
Temperature Co-efficient
It represents the stability of the capacitance value against temperature changes. Expressed in ppm/°C.
Frequency Range
It is the maximum frequency up to which the capacitor can work safely.
Dielectric Constant
It is the properties of the dielectric that affect the capacitance value.
Dielectric Strength
The ability of a capacitor to withstand voltage per unit thickness of dielectric material without breakdown. Measured in Kv/mm or Kv/cm. It depends on dielectric thickness, temperature, and power supply frequency.
Power Factor
Indicates the minimum loss of the capacitor. It indicates the percentage of input power that is dissipated as heat loss in the condenser. Lowering the power factor is the quality of the capacitor.
The reciprocal of the energy element is the high-satisfactory element (Q) of the capacitor. If the energy element is 0.001, the high-satisfactory element (Q) is 1000. Therefore, the high-satisfactory of the capacitor is high.
Color Coding In Capacitor
In color coding, the capacitance value is marked on the capacitor body using color. The paint color on the body of the capacitor is called the color range. All painted bands on the capacitor body refer to capacitance value and capacitance tolerance. Each paint color on the capacitor body represents a different number. Typically, capacitors are marked with four or more color bands.
4-Color Band Capacitor
In a four-band capacitor, the first and second color bands represent the first and second numbers of the capacitance of the capacitor. The 3rd color range represents the decimal, and the fourth color range represents the tolerance.
Capacitor In Series and Parallel Combination
Capacitor In Series Combination
If all capacitors are connected in series, the charge Q on each capacitor has the same magnitude V1 and V2 because the potential difference between C1 and C2 is different. The total value of the capacitors in the row is therefore equal to the reciprocal of the sum of the reciprocals of the individual capacitance.
Capacitor In Series Formula
| 1/CT = 1/C1 + 1/C2 + 1/C3 + …………1/Cn |
Capacitors In Parallel Combination
If the capacitors are connected in parallel, the potential difference V between the capacitors is equal and the charges on C1 and C2 are different. That is, Q1 and Q2. Therefore, the total capacitance or equivalent CT of the parallel circuit is equal to the sum of all the individual capacitors.
Capacitors In Parallel Formula
| CT = C1 + C2 + C3 + …………Cn |
Unit Of Capacitor
Capacitors are unitless devices. The capacitance of a capacitor is the ratio of the charge stored in one of the two conductors of the capacitor to the potential difference between the conductors. The SI unit for the capacitance of a capacitor is the farad (F).
Uses Of Capacitor
- Energy storage capacitor
- Power conditioning capacitor
- Capacitor as sensor
- Signal processing capacitor
Applications
- Capacitors are used to store electrical energy.
- To resist changes in applied voltage.
- Block DC and pass AC.
- For starting single-phase AC motors.
- Transmits high-frequency signals and blocks low-frequency signals.