Surge Types and Surge Protection Components

Surge refers to transient high-voltage noise caused by lightning and switching, etc.
A surge, in many cases, appears as a high voltage that far exceeds the allowable voltage range of parts and equipment.
Such a sharp surge of voltage breaks parts and equipment instantaneously.
What we collectively call a "surge" is actually classified into several types according to cause.
To prevent different types of surges, you need different surge protection components, respectively.
This article will discuss types of surges and surge protection components used against them.

Serge type

The graph on the right shows pictorial images of surges whose voltages and widths are plotted on the vertical and horizontal axes, respectively. Now we are going to explain the types of surges.

① Lightning surge

Lightning as natural phenomenon contains a very large amount of energy. A lightning surge can be grouped into direct lightning surges and induced lightning surges. Protection against a direct lightning surge is difficult, but protection against induced lightning is possible. Induced lightning is a high voltage surge induced by a relatively long wire such as power line or communication cable that is nearby a lightning strike.

② Open/close surge

Open/close surge is a transient high voltage surge induced in a switch or relay during its on and off operation, particularly when turning off, which causes rapid current change and inductance of the circuit or wiring. Voltage generated by an open/close surge is very high, and in some cases, it generates spark, heat or radiates an electromagnetic wave caused by a large damping oscillation current generated by floating static capacitance of inductance and contact. This high voltage surge may cause a malfunction of an electronic circuit, and in some cases, lead to the destruction of a component.

③ Load dump

Load dump is a surge generated by cutting the battery connection off on an automobile. The most severe instance occurs when the battery connection is lost while the automotive engine is in operation and the alternator (battery charging generator) is charging the battery. The magnitude of surge voltage is determined by the alternator rotation speed and magnetic field excitation strength at the moment of cut off.

④ ESD (electrostatic discharge)

ESD (electrostatic discharge) is a phenomenon where a charge is stored in a small floating capacity on a human body or substance then discharged to a nearby object, and is classified as one type of surge. ESD duration time is short with little energy, but because it generates transient high voltage as high as several kilo volts, it can generate a malfunction of electronic circuits or damages electronic components.

Surge protection component

The following table shows the types of surges and Panasonic surge protection components used against them. These components have a high electrical resistance when the terminal voltage is low, but the resistance suddenly becomes low when the voltage gets higher.
By using this tendency, the component prevents a surge from entering the circuit by bypassing the current when a high voltage surge occurs in an electric circuit.

Serge type Surge protection component Remarks
Lightning surge (Induced lightning surges) ZNR surge absorber Use different types (series) of surge absorbers for different line voltages (100 V to several kV) or different amounts of energy.
Open/close surge
Load dump SMD type (HF series)
ESD (electrostatic discharge) Chip Varistor Applied mainly to signal lines transmitting signals in kHz/MHz frequency bands and to low-voltage power lines.
ESD Suppressor Applied mainly to signal lines transmitting signals in GHz  frequency bands.

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