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Aviation plugs are electromechanical components that connect electrical lines. Therefore, the electrical parameters of the aviation plug itself are the first considerations when choosing an aviation plug.
1: Rated voltage, the rated voltage is also called the working voltage, which mainly depends on the insulating material used in the aviation plug and the distance between the contact pairs. Some components or devices may not be able to perform their proper functions when the voltage is lower than their rated voltage. In fact, the rated voltage of the aviation plug should be understood as the highest working voltage recommended by the manufacturer. In principle, aviation plugs can work normally below the rated voltage. The author tends to choose the rated voltage reasonably according to the withstand voltage (dielectric strength) index of the aviation plug, according to the use environment and safety level requirements. That is to say, the same withstand voltage index can be used at different high working voltages according to different use environments and safety requirements. This is also more in line with objective usage.
2: Rated current, rated current is also called working current. Like the rated voltage, the aviation plug can generally work normally when the current is lower than the rated current. In the design process of the aviation plug, the thermal design of the aviation plug is used to meet the rated current requirements, because when the contact pair has a current flowing, due to the conductor resistance and contact resistance, the contact pair will heat up. When its heat exceeds a certain limit, it will destroy the insulation of the aviation plug and form a contact to soften the surface coating, resulting in failure.
Therefore, to limit the rated current, in fact, it is necessary to limit the temperature rise inside the aviation plug not to exceed the specified value of the design. The problem to be paid attention to when choosing is: for multi-core aviation plugs, the rated current must be derated. This should be paid more attention to the occasion of high current. For example, the rated current of φ3.5 mm contact pair is generally specified as 50A, but it should be derated by 33% when using 5 cores, that is, the rated current of each core is only 38A. The more the number, the greater the derating.
3: Contact resistance, contact resistance refers to the resistance generated by two contact conductors at the contact part. There are two problems to be noticed when selecting. First, the contact resistance index of the aviation plug is actually a contact-to-resistance, which includes contact resistance and contact-to-conductor resistance. Usually, the conductor resistance is small, so the contact pair resistance is called contact resistance in many technical specifications.
Second, in the circuit connecting small signals, it is necessary to pay attention to the conditions under which the given contact resistance index is tested because the contact surface will be attached to an oxide layer, oil, or other pollutants, and the surface of the two contacts will produce film resistance. . When the thickness of the film layer increases, the resistance increases rapidly, making the film layer a poor conductor. However, the film layer will undergo mechanical breakdown under high contact pressure or electrical breakdown under high voltage and high current. The contact pressure designed for some small-sized connectors is quite small, and the application occasions are only at the mA and mV levels. The film resistance is not easy to be broken down, which may affect the transmission of electrical signals.
One of the contact resistance test methods in GB5095 "Basic Test Procedures and Measurement Methods for Electromechanical Components Used in Electrical Equipment" "Contact resistance - millivolt method" stipulates that in order to prevent the breakdown of the insulating film on the contact, the open circuit electromotive force of the test circuit The DC or AC peak value should not exceed 20mV, and the DC or AC test current should not exceed 100mA. In fact, this is a test method for low-level contact resistance. Therefore, selectors with this requirement should choose aviation plugs with low-level contact resistance indicators.
4: Shielding. In modern electrical and electronic equipment, the density of components and the related functions between them are increasing, which puts strict restrictions on electromagnetic interference. Therefore, aviation plugs are often enclosed with metal shells to prevent internal electromagnetic energy from radiating or being interfered with by 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.
Yuyao Jiying Electric Co., Ltd. is a China wire and plug manufacturer and wire and plug factory, we provide wholesale safe and reliable standard wires and plugs for sale all over the world, welcome to consult.
