What are the selection methods of electrical connectors?
2022-12-20
Connectors are electromechanical components that connect electrical circuits. Therefore, the electrical parameters of the connector itself is the first issue to consider when selecting a connector. The correct selection and use of electrical connectors is an important aspect of ensuring the reliability of the circuit.
Electrical connectors (hereinafter referred to as connectors) can also be called plug holders, widely used in a variety of electrical circuits, the effect of connecting or disconnecting the circuit. Progress in the reliability of the connector is first of all the responsibility of the manufacturer. However, due to the complexity of the connector type, the use of a wide range, therefore, the correct selection of connectors is also an important aspect of the progress of connector reliability. As long as the manufacturer and the use of the two sides of the joint efforts, in order to Z maximize the function of the connector should play.
Connectors have different classification methods. According to frequency, there are high-frequency connectors and low-frequency connectors; according to the shape of a circular connector, rectangular connectors; according to the use of points, there are printed circuit board connectors, cabinet connectors, audio equipment connectors, power connectors, special connectors and so on. The following is the primary discussion of low-frequency connectors (frequency of 3MHZ or less) selection methods.
Electrical parameters required
Connectors are electromechanical components that connect electrical circuits. Therefore, the electrical parameters of the connector itself is the first issue to consider when selecting a connector.
Additional voltage
Additional voltage, also known as operating voltage, it depends primarily on the insulation materials used to connect the machine, touch the size of the spacing between pairs. Some components or devices below its extra voltage, may not be able to complete its proper function. The additional voltage of the connector should in fact be understood as the manufacturer's recommended Z high operating voltage. Guidelines say that the connector can operate properly below the extra voltage. I tend to be based on the connector's voltage (electrical strength) indicators, in accordance with the use of the environment, safety level requirements to the reasonable use of additional voltage. That is, the same voltage indicators, according to the different application environments and safety requirements, can be applied to different high operating voltage. This is also more in line with the objective use of the situation.
Additional current
Extra current is also called operating current. The same as the extra voltage, in the case of less than the extra current, the connector can generally operate normally. In the connector planning process, is through the thermal planning of the connector to meet the extra current requirements, due to the touch pair with current flow, due to the existence of conductor resistance and touch resistance, the touch pair will be hot. When its heat exceeds a certain limit, it will damage the insulation of the connector and constitute a softening of the touch pair exterior coating, causing problems. Therefore, to restrain the extra current, in fact, to restrain the temperature rise inside the connector does not exceed the planning of the rule value. In the selection of the issue to be noted is: for multi-core connectors, the additional current must be used in derating. This should pay more attention to the occasion of high current, for example, φ3.5mm touch pair, the general rule of its extra current of 50A, but in 5 cores to derate 33% of the use, that is, the extra current of each core as long as 38A, the more cores, the greater the derating range.
Touch resistance
Touch resistance refers to the resistance of two touch conductors in the touch part. In the selection of two issues to note, one, the connector's touch resistance indicator is in fact the touch to resistance, which includes touch resistance and touch to conductor resistance. The general conductor resistance is small, and thus the touch-to-resistance is referred to as touch resistance in many technical specifications. Second, in the connection of small signal circuits, pay attention to the conditions under which the given touch resistance indicator is tested, because the touch surface will be attached to the oxide layer, oil or other contaminants, the two touch parts will produce a film layer resistance on the surface. When the thickness of the film layer increases, the resistance increases rapidly and the film layer becomes a bad conductor. However, the film layer will produce mechanical breakdown under high touch pressure, or electrical breakdown under high voltage and current. For some small volume of the connector planning the touch pressure is appropriately small, the application is only mA and mV level, the film layer resistance is not easy to be breakdown, may affect the transmission of electrical signals. In GB5095 "electric in the equipment with electromechanical components fundamental experimental procedures and measurement methods" in the touch resistance test method one of the touch resistance - millivolt rule, in order to prevent the touch on the insulating film is broken, test circuit open circuit electric potential of DC or AC peak value should be no greater than 20mV, DC or AC experimental current should be In fact, this is a low-level touch resistance test method, therefore, the selection of this requirement, because of the use of low-level touch resistance indicators of the connector.
Shielding
In modern electrical and electronic equipment, the density of components and their related functions between the increasing number of electromagnetic disturbances put forward a strict constraint. So the connector is often closed with a metal shell to block the internal electromagnetic energy radiation or by the outside electromagnetic field disturbance. At low frequencies, as long as the magnetic material can play a significant shielding effect on the magnetic field. At this point, there are certain rules for the electrical continuity of the metal shell, which is the shell touch resistance.
