You might have seen capacitors being used for suppressing any noise or to provide sudden surge currents. The basic types of capacitors that we use are electrolytic, ceramic and tantalum. There are several other types in common use of which spark gap capacitor is one type.
What do we use for ESD and lightening protection in circuits?
We often use ESD or TVS diodes in such cases. Spark gap is one type of capacitor that can be used in place of these diodes.
What are the advantages of these spark gaps?
These spark gaps can be constructed on the PCB itself without any physical component which itself is a very low cost implementation. These spark gaps can handle high voltage transients (in kV) as such they an be used for ESD and lightening protection. they have a rugged construction and chances of failure are less. they can handle large surge currents.
How is a spark gap capacitor constructed?
The genuine functionality of spark gap is same as normal capacitor but they differ in construction. A spark gap is formed by separating two electrodes with a air gap. One of the electrode is connected to ground.
How does a spark gap operate?
Spark gaps when constructed have a break down rating. when a voltage transient voltage reaches that breakdown voltage value, this spark gap provides a low impedance path to ground. When electrons flow through this low impedance path they collide with the molecules in the air and their electrons get excited and jump to higher orbital levels. So, when they jump back to their normal levels, they emit light. due to which we see a spark. Sometimes, we also hear sounds in case of lightening strikes. So, once the transient voltage goes below spark gap breakdown, the operation comes to normal and the conducting path between the two plates is no more there. even in case, the current goes below a limit specified by holding current, the conductivity between plates is lost. You may observe some heat also being produced in a spark gap.
Spark gap voltage can be calculated by the formula: (3000 * atmospheric pressure * plate distance + 1350)
the only problem with spark gap, this breakdown voltage is always varying.
Symbolic representation of spark gap in a circuit:
Where do we use this spark gap?
What do we use for ESD and lightening protection in circuits?
We often use ESD or TVS diodes in such cases. Spark gap is one type of capacitor that can be used in place of these diodes.
What are the advantages of these spark gaps?
These spark gaps can be constructed on the PCB itself without any physical component which itself is a very low cost implementation. These spark gaps can handle high voltage transients (in kV) as such they an be used for ESD and lightening protection. they have a rugged construction and chances of failure are less. they can handle large surge currents.
How is a spark gap capacitor constructed?
The genuine functionality of spark gap is same as normal capacitor but they differ in construction. A spark gap is formed by separating two electrodes with a air gap. One of the electrode is connected to ground.
How does a spark gap operate?
Spark gaps when constructed have a break down rating. when a voltage transient voltage reaches that breakdown voltage value, this spark gap provides a low impedance path to ground. When electrons flow through this low impedance path they collide with the molecules in the air and their electrons get excited and jump to higher orbital levels. So, when they jump back to their normal levels, they emit light. due to which we see a spark. Sometimes, we also hear sounds in case of lightening strikes. So, once the transient voltage goes below spark gap breakdown, the operation comes to normal and the conducting path between the two plates is no more there. even in case, the current goes below a limit specified by holding current, the conductivity between plates is lost. You may observe some heat also being produced in a spark gap.
Spark gap voltage can be calculated by the formula: (3000 * atmospheric pressure * plate distance + 1350)
the only problem with spark gap, this breakdown voltage is always varying.
Symbolic representation of spark gap in a circuit:
Where do we use this spark gap?
- As spark plug in automobiles
- For ESD protection of interfaces in a electronic circuit
- We see them at the input of transformer in a AC-DC circuit
- other general uses are CRTs, X-ray machines
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