Md. samim Sk
August 18, 2017
0
Introduction to Capacitors
- A capacitor is a passive electronic component used to store electric charge.
- The unit for measuring capacitance is Farads.
- The standard capacitor values are 1, 10,100,510,910pF
- Capacitors are also marked with color bands to denote value.
- The first 2 bands are the first and second digit whereas the third band denotes the multiplier.
- Symbol for capacitor is shown.
- Capacitor tolerance is the value which determines the extent to which capacitance can vary from actual capacitance.
- It ranges from 20% to +80%
- Temperature Coefficient
- The temperature co efficient is the maximum change in a capacitance with change in temperature.
- It is measured in ppm/◦C (Parts per million by degree Celsius)
- The factors affecting capacitor behavior are as follows:
Breakdown voltage, Equivalent circuit, Q factor, Ripple current, Instability, Dielectric
absorption, Leakage, Current and Voltage Reversal
- Breakdown voltage: The voltage at which the dielectric capacitor becomes conductive is called
breakdown voltage.
- Equivalent circuit: All capacitors also have some resistance called Equivalent series resistance which adds up to the impedance.
- Q factor: It is used to measure efficiency and is the ration of its reactance to its resistance.
- Ripple current: Ripple current is the component of AC which generates heat in the capacitor.
- Instability: As the capacitors begin to age, capacitance of certain capacitors decreases.
- Dielectric absorption: Capacitors containing dielectric material show dielectric absorption which generates voltage.
- Leakage: Constant exposure to heat causes leakage in dielectric.
- Current and Voltage Reversal: Current reversal occurs when current changes direction and voltage reversal occurs when there is change in polarity and these reversals cause excessive heating in capacitor.
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