The Power electronics system uses different types of capacitors for power conditioning and signals conditioning applications.
Therefore, in some applications, the capacitors required to handle a large amount of power. As a result, it must be capable to handle a large amount of current without damage and overheat.
The capacitors must be close to their ideal characteristics namely low equivalent series induction and low equivalent series resistance.
Low equivalent series induction ensures that the capacitor used in a large range of operating frequencies. Low equivalent series resistance ensures the low losses of the capacitors.
There are several types of capacitors available for different applications of power electronics engineering.
Types of capacitors
- Coupling capacitor
- Power capacitor (low frequency)
- Power capacitor (high frequency)
- Filter capacitor
- Pulse capacitor
- Damping capacitor
- Commutation capacitor
- Resonant capacitor
1) Coupling capacitor
This type of capacitor used to transfer AC voltage between two circuits at a different average potential. The current carried by this capacitor is very low.
High insulation resistance is an important feature of these capacitors.
Such type of capacitor used in the control circuit to couple AC signals forms one circuit to another circuit at different DC potentials.
2) Power capacitor (Low frequency)
The low-frequency power capacitors used to improve the power factor. For that, it compensates the demand for reactive power of the load.
So, the power handling portion will not supply reactive power. Further, they bypass the harmonics generated by the system.
This type of capacitor used only for the low-frequency application (50 Hz / 60 Hz) where the voltage is predominantly sinusoidal and the current may be rich in harmonics.
This capacitor has the capability to handle high reactive power and high harmonic current.
3) Power capacitor (High frequency)
This capacitor is capable to carry the surge current produced from the switching. It can be used in the same application as the low-frequency capacitor but at a higher frequency up to 20 kHz.
This type of capacitor used in the application like the varying load condition where the capacitor bank must be ON and OFF according to the load condition. A similar condition creates in the power system and induction heating applications.
This type of capacitor is capable to handle large reactive power, switching surge current and able to operate at a higher frequency.
4) Filter capacitor
These capacitors are electrolytic capacitors on account of unipolar voltage. There are two types of filter capacitors; forward filtering capacitor and reverse filtering capacitor.
The forward filtering capacitor used to smooth out the variable source voltage applied to the load.
And the reverse filtering capacitor used to smooth out the variable load current from reaching to the source.
This capacitor has a high capacitance value and a high RMS current rating. The filter capacitors were able to handle large periodic currents.
5) Pulse capacitor
Pulse capacitor used to provide high surge current to the load for a small time. They will be charged over a relatively long period and discharge in a very short period This capacitor used in applications like precision welding, electronic photo flash, and electronic ignition.
This capacitor has large energy storage capacity, large peak current handling capacity and low equivalent series inductance.
6) Damping capacitor
This capacitor is also known as the snubber capacitor. To suppress the undesired voltage stress on the device, these capacitors connected in parallel with the power switching device.
The RMS current of this capacitor is high and it has low equivalent series inductance.
7) Commutation capacitor
The SCR is not a fully controlled device. The commutation circuit used for forced turn off the device. These capacitors used in the commutation circuit.
The commutation process is quite short and so these capacitors must have purely capacitive reactance even at the high operating frequency.
These capacitors have a high peak current capacity and low equivalent series inductance.
8) Resonant capacitor
The resonant capacitor used in a circuit with the inductor. This circuit used to make voltage and current signal sinusoidal.
The operating frequency of the resonant capacitor is high. This type of capacitor is stable and has low equivalent series resistance.
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