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Factors affecting contact resistance in a pressure relay

Author : Zhou Date : 2/7/2018 10:17:33 PM
Factors affecting contact resistance in a pressure relay
In a pressure relay, contact resistance is an objective phenomenon, and any contact is unavoidable. However, when we understand its essence and grasp its characteristics, we can then analyze its influencing factors and take corresponding measures to reduce or eliminate its influence.
Do these hazards of contact resistance show up in any situation? Not really. Because the occurrence of this hazard is closely related to the circuit parameters close to the contact point. The circuit parameters are different, and the properties and harms of contact resistance are different. For example, when the contact is used to close the large high voltage, current, contact on the surface of the membrane can be larger and contact pressure or crushed by breakdown voltage, single slip burned without cause of failure. At this point the main point of the contact will be the strong current flowing through the contact at the contact point due to contact resistance caused by the heat. If the design and use is improper, sleep makes the contact temperature exceed the prescribed standard and even produce fusion welding. Therefore, how to avoid contact overheating or welding is the key to this kind of electrical contact. In another case, when the contact is used to connect, small voltage and current through the contacts because on the surface of the membrane due to breakdown or will not be destroyed, its harmfulness is prominently shown, seriously affecting the reliability of this kind of relay work. Therefore, if we try to reduce and stabilize the film resistance, it becomes the most important and prominent problem of the contact point of the pressure relay.
In fact, we can start with several aspects:
Contact pressure, any contact must add a certain contact pressure when working in a closed state. Its function and, on the one hand, are the contact area of the exposed voltage, which increases the contact area of these points, and at the same time makes more points contact, thus reducing the contact resistance. In this way, the heat of the contact is greatly reduced when it flows through the same current. Or, under the same heating conditions, the current allowed to pass can be greatly improved. The action of contact pressure can also be used to resist heat or melt welding. Obviously, the larger the contact pressure, the smaller the contact resistance, the larger the current that is allowed to pass. Usually, the contact pressure of a larger capacity is determined from this principle. That is, the protection point should not be softened by the rated current, and the overload current should not be melted because of overheating. For example, half of the control with a large power relay, the contact pressure is often 50~ 100g; The contact pressure of the contactor or automatic switch is a few hundred grams to dozens of kilograms. Another function of the contact pressure is that the surface film can be broken and direct contact with the contact metal, so that the contact resistance can be reduced and stabilized, which is known as the clearance capacity.
Contact pressure of the third role, is that it can resist vibration and impact of the outside world, guarantee not because of these factors and make the contact resistance increases even make contact instantaneous leave the power outage. This effect is called seismic resistance. But food always has two sides. Excessive pressure will increase the operating force, which will increase the size of the battery system and so on, resulting in reduced sensitivity of the pressure relay. Therefore, in the high sensitive pressure relay, the contact pressure cannot be too large, and the contact capacity is very small. This is really the result of an induction and execution of a pair of contradictory decisions.

The above:Analysis of the cause of reverse flow failure of hydraulic oil