Reaction characteristics of power control relays 01

We know that in a power control relay with contacts, the main task of the contacts is to "open" and "close" the circuit, so there are only two forms of movement: "divide" and "close". This "opening and closing" movement of the contact system is mainly based on the combined action of the force generated by the return spring (or reed) and the mechanical force transformed by the external input signal (this is the force in two opposite directions). Completed. That is to say, only when the input signal is small enough that the mechanical force converted by it is smaller than the force of the return spring,

The "divided" movement can occur: Conversely, only when the input signal is large enough that the mechanical force transformed by it is greater than the force of the return spring, the "closed" movement can be produced. Therefore, the two forces that exist in the power control relay at the same time are interdependent and opposed to each other, and they constitute a pair of contradictions. When the external conditions change the magnitude of the input signal, the positions occupied by the contradictory two parties will be transformed due to the struggle: or the force of the return spring becomes the main aspect of the contradiction, which determines the movement of the "point" of the contact point; Or the mechanical force converted from the input signal rises to the main aspect of the contradiction, which determines the movement of the "joint" contact point. Here, as the return spring on the contradictory side, it plays the role of comparing and judging the external signal, so the size and characteristics of the force it generates determine the sensitivity of the power control relay action and the accuracy of the opening and closing movement. and reliability. Therefore, before we study the other side of the contradiction and its interdependent struggle relationship, we must first analyze and discuss its characteristics and laws. Let's take the electromagnetic power control relay as an example to illustrate it.

In the electromagnetic power control relay, the electromagnetic attraction force converted by the input signal and the force of the return spring (or reed) act on the armature, and their directions are opposite, and the latter is customarily called the reaction force. However, the reaction force usually referred to in the power control relay (and other electrical appliances), in addition to the force generated by the main aspect of the return spring, also includes the force of the normally open and normally closed contact springs (or reeds). weight, friction between the movable part and the stationary part and other resistances, etc. Or, so-called The reaction force of the power control relay refers to the algebraic sum of all mechanical forces actually acting on the armature except the electromagnetic attraction force. Why algebraic sum? Because some of the forces, such as the force and friction of the normally closed contact reed, are not all opposite to the direction of the electromagnetic attraction, but are customarily counted in the reaction force. However, the weight of the movable part in the power control relay is usually small, and if the processing and coordination are good, the frictional resistance on the shaft is also very weak, so it can be ignored. Or in order to highlight the main contradiction,For the analysis, the influence of weight and frictional resistance will not be considered in the following discussion, and the force generated by the return spring and the contact spring will be analyzed. Moreover, since the armature moves under the action of the force, it in turn makes the magnitude of the force of the spring vary.

Therefore, what we want to study is not the force of the static spring, but the regularity of its change with the movement of the armature, that is, the change of the air gap (the air gap between the armature and the static core column). The regularity that the reaction force changes with the air gap is called"Reaction Characteristics".

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