The performance of vacuum arc extinguishing chamber determines the performance of contactor, and the mechanical characteristics of contactor itself also determine the performance of vacuum arc extinguishing chamber.Whether the performance of a vacuum contactor meets the requirements mainly depends on whether its mechanical characteristics meet the requirements of the matching vacuum arc extinguishing chamber.
First, the first look at the contact pressure.When the vacuum arc extinguishing chamber acts without an external force, the dynamic contacts close with the static contacts under the action of atmospheric pressure, which is called the autistic force.The size of the force depends on the port cross-sectional area of the bellows. Generally, the closing force can not guarantee the qualified electrical contact between the dynamic and static contacts of the vacuum arc extinguishing chamber, and an external pressure is superimposed.The size of this pressure depends on three factors: a. The rated current of the arc chamber; b. The arc chamber contact material; c. Electric repulsion between dynamic and static contacts when the arc chamber is closed.According to these factors to choose the appropriate applied pressure, the closure force and the superimposed external pressure are called the contact pressure of the contact head, also called the terminal pressure.
2. The role of the terminal pressure on the contactor.Reasonable terminal pressure, Ensure the qualified contact resistance between the dynamic and static contacts of the arc extinguishing chamber, Contact resistance can be measured by a circuit resistor; Reasonable terminal pressure, It can meet the requirements of the dynamic heat stability of the vacuum arc extinguishing chamber, Can overcome the repulsion between the contacts in the high current state, To ensure complete closure without damage, That is, the contacts will not stick to death; Reasonable terminal pressure, Can reduce the be reduced, The impact force that causes the contact when closed, Absorbed by the elastic potential energy; Reasonable terminal pressure, In conducive to switch characteristics, When the terminal pressure meets the requirements, The contact spring compression is also large, The elastic potential energy is also large, To increase the initial speed of the switching gate, Reduce the burning arc time and improve the switch capacity.
Three, the definition and function of overtravel.Any vacuum switch is closed in overstroke mode, when closed, the dynamic contacts can not move forward after contacting the static contacts, but the pressure between the dynamic contacts need.This pressure is realized by the contact spring. When the movement and movement collide, the force on the contact spring will continue to move. The displacement distance during the movement is the compression stroke of the contact spring, which is the overstroke.In addition to increasing the initial speed of the switch, overstroke has two important functions: a. The force of the contact spring is transmitted to the contact pressure between the contacts to meet the needs of operation; b. After the long operation of the contactor, the contacts will burn and reduce the total thickness of the contacts. If reasonable overstroke is guaranteed, a certain terminal pressure can make the vacuum contacts work normally.In fact, the contact pressure spring has given the compression of the contactor switch state, which is to close the contact moment, to reach the prepressure value to reduce the closing bounce, when the overstroke movement ends, the terminal pressure also meets the design requirements.
Post time: Apr-25-2022
