Why Capacitors use as High Voltage protection:
The voltage across the capacitor cannot change instantaneously. This property is used in high voltage protection in electronics circuits. Let see how?
As we know the current i flow through the capacitor is given by,Get More Electrical Concept And Interview Questions By Using This Link
Instantaneous is nothing but the changes at zero time. That means if the capacitor across the voltage changes instantaneously, then dv/dt= infinity, hence the current through the capacitor also infinity, it is highly not possible. That’s why the voltage across the capacitor cannot change instantaneously.
Example: Snubber circuits.
How the Snubber capacitor circuit Work:
The Snubber circuit is nothing but a capacitor is connected across the device to be protected. i.e Example take an IGBT circuit. Here the blue color components (marked in yellow ring) is called Snubber circuit.Get More Electrical Concept And Interview Questions By Using This Link
During Normal condition, the capacitor charges upto the input voltage of the source (Normally, input voltage = capacitor voltage). During abnormal condition i.e if circuit experience a voltage peak or When the input voltage rises the capacitor starts charging. Hence the voltage peak will get suppressed because of capacitor does not allow sudden voltage changes in the circuit. The equipment to be protected (IGBT or any thyristor) will be protected.
- Capacitor does not allow sudden voltage changes across it.
- Snubber work as a perfect high voltage (instant) protection for all electronics equipment.
- Snubbers are mainly used where the rectifier output needed circuits
Response of a Capacitor in a DC source:
Connect a capacitor with DC source, Where the voltage across a capacitor is DC, then the current through the capacitor i is..
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Because in DC the voltage does not vary with respect to time, therefore
Therefore, the current through the capacitor is zero. Hence the capacitor acts as an open circuit.