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Time: 06, 07 2021 Views: 191
The conductive slip ring is an extremely important component in the automation control system. It provides a channel for power and information transmission for the system. Therefore, the electrical performance parameters of the customized slip ring become particularly important. Its performance is directly related to the stability of the entire system. The main electrical properties of the custom slip ring are briefly introduced below to prevent safety accidents caused by wrong parameters!
1. Rated voltage and current
The rated voltage is also called the working voltage. It mainly depends on the insulating material used by the machine and the distance between the contact pairs. Some components or devices may not be able to perform their due functions when the voltage is lower than their rated voltage. The rated voltage of the connector should in fact be understood as the highest working voltage recommended by the manufacturer. In principle, the connector can work normally at a voltage lower than the rated voltage. According to the withstand voltage (electric strength) index of the connector, the rated voltage should be reasonably selected according to the use environment and safety level requirements. In other words, the same withstand voltage index can use different maximum working voltages according to different use environments and safety requirements. This is also more in line with objective usage conditions. Rated current is also called working current. Like the rated voltage, the connector generally works normally when it is lower than the rated current. In the connector design process, the thermal design of the connector is used to meet the rated current requirements, because when current flows through the contact pair, the contact pair will generate heat due to the presence of conductor resistance and contact resistance. When its heat exceeds a certain limit, it will destroy the insulation of the connector and form a contact to soften the surface coating, causing malfunction. Therefore, to limit the rated current, in fact, the temperature rise inside the connector should not exceed the specified value of the design. The problem to pay attention to when choosing is: For multi-core connectors, the rated current must be derated for use. This should be paid more attention to in the case of high current.
Second, the material of the slip ring
The function of the slip ring is to electrically connect and transmit power and signal, and the first choice must have excellent electrical contact performance. Since the contact method of the conductive ring is electrical sliding contact, it needs to have abrasion resistance and electrical corrosion resistance. We know that Ag is the best for conductivity, followed by Cu, Au, Al. However, these metals have low hardness and poor wear resistance. In order to make up for this shortcoming, we will add other metal elements to these metals according to actual application requirements. Increase material hardness to enhance wear resistance, commonly known as ternary alloy!
Slip rings need to transmit a variety of different signals in a restricted space, such as high-frequency alternating current, high-voltage alternating current, high-current alternating current, and weak direct current small signals. Due to the close distance between the rings, various signals will be generated during the signal transmission process. Interference, resulting in distortion of the transmitted information. For general magnetic interference, we use electromagnetic shielding; for electrical interference, we use electric field shielding to reduce interference.
Fourth, insulation performance
Insulation performance is the safety performance of slip rings, including insulation between loops, insulation between loops and shells, insulation between wires, insulation between loops and wires, insulation between loops and wires and shells. Insulation performance depends on the insulating material. Depending on the production process and use environment of the slip ring, different production processes, the materials and shapes of the insulating materials we use are different, usually we need to consider the insulation properties of the insulating materials, aging resistance, water absorption, fire resistance, High temperature resistance and mechanical strength. It is very important to choose the right insulation material for different applications.
Five, contact resistance
Contact resistance refers to the resistance generated by two contact conductors at the contact portion. Two problems should be noted when selecting. First, the contact resistance index of the connector is actually the contact-to-resistance, which includes contact resistance and contact-to-conductor resistance. Usually the conductor resistance is small, so the contact-to-resistance is called contact resistance in many technical specifications. Second, in circuits that connect small signals, pay attention to the conditions under which the given contact resistance indicators are tested, because the contact surface will be accompanied by oxide layers, oil stains or other contaminants, and film resistance will occur on the surfaces of the two contacts. . When the film thickness increases, the resistance increases rapidly, and the film becomes a poor conductor. However, the film may undergo mechanical breakdown under high contact pressure, or electrical breakdown may occur under high voltage and large current.
In modern electrical and electronic equipment, the density of components and their related functions is increasing day by day, which imposes strict limits on electromagnetic interference. Therefore, the connector is often enclosed with a metal shell to prevent internal electromagnetic energy radiation or interference from external electromagnetic fields. At low frequencies, only magnetic materials can significantly shield the magnetic field. At this time, there are certain regulations on the electrical continuity of the metal shell, that is, the shell contact resistance.
Seven, pressure resistance
Withstand voltage is the critical voltage that can withstand higher than the rated voltage within a specified time between the mutually insulated parts of the contact pair or between the insulated part and the ground without causing breakdown. It is mainly affected by contact spacing and creepage distance and geometry, insulator material, ambient temperature and humidity, and atmospheric pressure.
Any connector is inseparable from current when it is working, so there is a risk of fire. Therefore, the connector is required not only to prevent ignition, but also to self-extinguish in a short time once it ignites and catches fire. When selecting, pay attention to choosing electrical connectors that use flame-retardant, self-extinguishing insulating materials.