How to choose the right contactors? Epoxy sealed or Ceramic sealed?

Two typical technical routes in high voltage contactors/relays (ceramic sealed and epoxy sealed)

Ceramic sealed, this technical route is represented by Panasonic; the other one is epoxy sealed, which is represented by TE.

Why is the high-voltage DC relay inflated? What is the arc-extinguishing principle of the gas? Why ceramic contactor filled with hydrogen and the epoxy contactor is filled with nitrogen? The difference between DC and AC is mainly that the DC has no zero-crossing. Once an arc is formed, it will not extinguish itself and will continue to arc. This is a fatal damage to the contacts! What is the nature of the arc? It is the escape of electrons under the action of electric field force, which is an extreme discharge. Therefore, there are two methods for arc extinguishing, one of which is to increase the contact gap (the essence of magnetic blowout is to use the Lorentz force to change the path of the arc, which can be understood as increasing the contact gap, if only physically Increase the contact gap without magnetic blowout, the corresponding relay magnetic gap is also large, the same load capacity, the size and weight cannot be imagined). Another way is to find a dielectric material between the contacts. The best way is filling gas. The first requirement is that the gas is very active. When the gas is active, it is more likely to collide with the electrons that the arc escapes, which has a blocking effect and is easier to take away heat. The second requirement is that the molecular structure of the gas is very stable, and electrons are not easily escaped. Based on above two requirements, hydrogen is the best choice for arc extinguishing. The molecular weight of hydrogen is the smallest and most active in all gases, and the molecular structure is also stable enough. Why some contactors are filled with nitrogen? Because of their epoxy encapsulated. Hydrogen is the best arc-extinguishing gas, but its molecular weight is small and must be sealed to avoiding leaking. Epoxy can’t seal Hydrogen well, Nitrogen will be a better choice for epoxy sealed contactor.

Different ways of arc-extinguishing makes the contactors different in size, service life and price. There is no absolute advantage, only choose the right one suitable for your application.

High voltage DC contactor-EVH Series                                   DC Contactor for photovoltaic, wind power and energy storage system

 EVH series (ceramic sealed)                        EVQ series (epoxy sealed)   

We can both offer epoxy sealed and ceramic sealed contactors, call or drop email to for more detailed information.