The principle of spring contact finger, spring contact finger as an elastic contact, it is installed between two rigid input and output electrical contacts. After compressing a certain amount, the elastic force is generated, which ensures reliable contact.
The principle of spring contact fingering is as follows:
There are many contact points, each spring coil is a contact point, equal to many circuits in parallel, the more contact points, the more turns, the smaller the contact resistance, the more shunting, the smaller the current flowing through each turn. The number of turns is large, the current distribution is even, and the heat dissipation is good.
The relatively large scale of stable contact force value and the large scale of stable contact force value can ensure that the contact resistance does not change at all in the vibration state.
Based on the spring contact finger, it can have different shapes of contact fingers, single surface contact, double surface contact, round surface contact and so on.
The contact resistance of the single-turn spring contact finger is 4-5 microohms, taking 50 turns of contact as an example, the resistance is 0.1 microohms, the resistance is very small, and the heat loss is very small.
Beryllium bronze has high hardness and strength. The strength of zirconia copper is more suitable. The contact friction is small, more than half less than the friction of the plum blossom contact, especially the high-current contact, 3150/4000A contact 82 fingers, the pressure is large, the circuit breaker shakes in and out of the torque, which is very difficult, and the spring contact finger does not require a lot of operating force.
Plum blossom contact adopts silver plating treatment, but because the contact pressure is large, and the demand is often in and out, the wear and fall off of the silver plating layer will lead to copper as an anode agile corrosion, lose its excellent conductive function, to threaten the safety of power grid operation, now the new technology is to use the contact substrate material copper corrosion behavior under current, the preparation of silver-graphene composite plating, to improve the corrosion resistance and wear resistance of the contact material. Because of the high hardness, excellent wear resistance and corrosion resistance of the coating, but the cost is too high.
The spring contact finger is selected because the pressure is small and there are many contact points, so the contact wear is small, and it is shaken in and out 10,000 times. And the outer diameter is small, the current carrying capacity is large, the ability to resist short circuit is strong, and the electric field of the contact system is uniform.
Many people will worry about the alignment problem of spring contact fingers used in the withdrawal circuit breaker, in fact, after improving the accuracy, the positioning pin is positioned in advance, which can fully ensure the requirements of spring contact finger +/-1mm.
Spring tentacles don't have to be round. Other shapes can be made for different uses, such as rectangular contacts for frame circuit breakers, single-sided contacts for low-voltage drawers, etc.
