Capacitors in Parallel and Series Connection

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Table of Contents

Description and Presentation
Photoflash Capacitor
Tunable Antennas Capacitors
Example: Equivalent Capacitance in Parallel and Series Combined Arrangement
Real World Problem: Electrical Hazards
References

Description and Presentation

In the series connection of capacitors, the total capacitance becomes lesser than the capacitance of individual capacitors (Aguzzoli, 2018). Connecting two or more capacitors in series results in the equivalent capacitance equaling the total sum of each capacitor’s plate spacing. Therefore, increased plate spacing in capacitors causes a decrease in capacitance.

On the other hand, the parallel arrangement of capacitors results in the total capacitance becoming the total sum of each capacitor’s capacitance (Aguzzoli, 2018). The overall effect of connecting two or more capacitors in parallel is described as an individual equivalent capacitor bearing the total of capacitor plates of each capacitor (Aguzzoli, 2018). An increased capacitor plate area leads to increased capacitance, as in the parallel arrangement of capacitors.

Therefore, the properties of capacitors in parallel have been exploited to develop significant real-world components such as photoflash and tunable antenna.

Photoflash Capacitor

Typically, photoflash capacitors power high-voltage flash tubes. The flash tubes then irradiate photographic targets or use optics to pump laser rods. Operating flash tubes require very high currents. Thus photoflash capacitors must be designed to carefully supply “high discharge current pulses” without causing excessive heating internally. They have lower series inductance than electrolytic capacitors applicable in filtering power supplies based on the power frequencies (Aguzzoli, 2018). The low series inductance implies that the photoflash capacitors have high capacitance values, highly rated voltages, and reduced series resistance. Photoflash capacitors have standard voltages ranging between 300V and 330V and a normal capacitance range of 80-160 microfarads in most disposable cameras, while the capacitance value is higher in large flash units. Photoflash capacitors operate at a “maximum operating temperature” value of 55 °C (Aguzzoli, 2018). Additionally, larger professional photo flashes contain massive flash tubes and larger capacitors, thereby appropriately supplying power. Photoflash capacitors deliver high-current pulses. Hence they can also be applied in coil gun and rail gun designs.

Tunable Antennas Capacitors

Antennas use special variable capacitors called MEMS tunable capacitors. The capacitors comprise tunable substrates that offer variable capacitance without using the FET switch. The substrates are used to improve the quality factors of the capacitors (Khan & Younis, 2021). Additionally, the MEMS capacitors contain barium strontium titanate (BST), enhancing linearity. The mechanism of action of the MEMS-based antenna capacitors involves an electrostatic force that causes beam actuation (Khan & Younis, 2021). Downward placement of the beam switches on the capacitors since the beam is separated from the metal trace by a dielectric only. Upon being up, it is separated from the metal trace by an extra air gap; hence the capacitor turns off. Varactors can also achieve the tenability of the antenna. However, the flexibility of the varactors is limited by the limited maximum achievable capacitance and an increased bias voltage of the MEMS capacitors (Khan & Younis, 2021).

Example: Equivalent Capacitance in Parallel and Series Combined Arrangement

The capacitors one µF and 3µF are in parallel, and 6µF and 2 µF are also independently connected in parallel. Therefore, these parallel connections are simplified to equivalent single capacitance in their positions, as depicted in figure (b).

Ceq = 1µF + 3µF = 4µF

Ceq = 6µF + 2µF = 8µF

Figure (b): two 4 µF capacitors are connected in series, and the two 8 µF capacitors are connected in series. Using the formula for the series, we can reduce their equivalent capacitances, as shown in figure (c).

1/???????????? =1/4+ 1/4 = 1/2

Therefore, Ceq = 2 µF

1/???????????? =1/8+ 1/8 = 1/4

Therefore, Ceq = 4 µF

Figure (c) shows that 2µF and 4µF are connected in parallel. The equivalent capacitance is shown in figure (d)

Ceq = 2µF + 4µF = 6µ

Thus the combination of capacitances in figure (a) can be replaced by a single capacitance of 6 µF.

Real World Problem: Electrical Hazards

Capacitors in series arrangements tend to store so much hazardous energy that it can compromise electric safety standards. Even after a capacitor de-energization, the storage can continue, thereby accumulating hazardous residual charge lacking an outside source (Aguzzoli, 2018). The capacitors can explode upon exposure to high temperatures and currents. Therefore, large capacitors should be stored in parallel arrangements to mitigate the effects of charge build-up.

References

Aguzzoli, C. (2018). Impregnation technique assessment on the electrochemical behavior of an aluminium electrolytic capacitor. [Master Thesis].

Khan, F., & Younis, M. I. (2021). RF MEMS electrostatically actuated tunable capacitors and their applications: A review. Journal of Micromechanics and Microengineering, 32(1), 013002.

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