Double diode Symbol

[Sim1998]

Hello

Please for comments what is the purpose of this double diode? (picture attached)
It is connected on + and - on DC Voltage Generator (parallel to DC Generator) , for supply of DC voltage consumers: dc contactors, dc brakes,...

Thanks

 

[rjenkinsgb]

It looks like a transient voltage suppressor, such as a "Transil", the bidirectional type from the symbol.

They are something like a zener diode but intended to clamp voltage transients.
The symmetrical ones have the same clamp voltage in either polarity.

More info:

Transil Diode / TVS - Definition, Basics and Application

Transil Diode is the type of Semiconductor Diode designed to protect sensitive electronic circuits from electric surges. Find out more in this article.

911electronic.com

 

[Sim1998]

Thanks
Attached Real Picture of diode

 

[rjenkinsgb]

OK, it's actually an MOV, a "Metal oxide varistor", which does pretty much the same thing as a transil but using a different technology - it's classed as a kind of Voltage dependant resistor.

They start to conduct above a certain voltage and can dissipate very large amounts of energy to limit high voltage spikes.

This is the actual brand on yours:

Home - High Energy Silicon Carbide Varistors | Metrosil

Metrosil manufactures a wide range of high energy silicon carbide varistors, protecting some of the biggest infrastructural projects in the world.

metrosil.com

They have used the TVS symbol in the schematic; this is an MOV or VDR symbol:

https://www.electronicshub.org/wp-content/uploads/2014/12/schemeit-project-6.png