ALL YOU NEED TO KNOW ABOUT ELECTRONIC REPAIRS
Series and Parallel combination of capacitances
Like resistors, the series and parallel combination of capacitance is important in the servicing line. Sometimes it is difficult to get an exact capacitor value and voltage rating in the market, therefore you have to use the series and parallel combination of capacitance to achieve your desire capacitor value and voltage rating for replacement.
Capacitors in Series
In series combination the distance between the plates increases, so the total capacitance is reduced when the capacitors are connected in series. The net capacitance is less than the lowest capacitance present in the series circuit. The results is exactly the same as the resistances in parallel. If the capacitors of 1 microfarad each are connected in series, the net capacitance offered by the combination of the two capacitors is: -
So the net value is just half of an individual capacitor. Capacitors are used in series to provide a higher voltage breakdown rating for the combination.
When electrolytic capacitors are to be connected in series, connect positive to negative exactly as when connecting batteries in series. (Fig. 1)
In series capacitors, the working voltage of each capacitor is added. This series connection provides a reduction in capacitance but an increase in working voltage.
The net value of this combination is: -
but the working voltage becomes 700V.
Capacitors in Parallel
When capacitors are connected in parallel their value is added up. The reason is that the capacity is increased due to larger plate surface area. The formula for parallel capacitor is same as the resistance in series.
If 5, 10 and 15 microfarad capacitors are connected in parallel (Fig 2), the combination would provide a net capacitance of 30 microfarad.
When electrolytic capacitors are connected in parallel, check polarity connect positive to positive and negative to negative.
But the working voltage of parallel capacitor is equal to the lowest working voltage rating in the combination. For example, the net capacitance of the combination is:-
CT = C1 + C2 + C3
CT = 1µF + 2µF + 1µF = 4µF
working voltage = 100v
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