Introduction Of Aviation Plug
Aviation plug
Aviation plugs are electromechanical components that connect electrical circuits. Different electrical parameters have different related products, so choosing the right aviation plug is a very important topic!
Aviation plugs can also be called plug sockets, which are widely used in various electrical circuits and play the effect of connecting or disconnecting circuits. Improving the reliability of aviation plugs is first and foremost the responsibility of the manufacturer. However, due to the variety of aviation plugs and the wide range of applications, the correct selection of aviation plugs is also an important aspect of improving the reliability of aviation plugs. Only through the joint efforts of the manufacturer and the user, can the function of the aviation plug be maximized.
There are different classification methods for aviation plugs. According to the frequency, there are high-frequency aviation plugs and low-frequency aviation plugs; according to the shape, there are circular connectors, according to the purpose: aviation plugs for cabinets, aviation plugs for audio equipment, power aviation plugs, special-purpose aviation plugs, etc. The following mainly discusses the selection method of low-frequency aviation plugs (frequency below 3MHZ).
Aviation plug
Security parameter modification
1: Insulation resistance
Insulation resistance refers to the resistance value that occurs when a voltage is applied to the insulating part of the aviation plug, so that leakage current occurs in or on the surface of the insulating part. It is mainly affected by factors such as insulation material, temperature, humidity, pollution and so on. The insulation resistance value provided on the aviation plug sample is generally the target value under the standard atmospheric conditions. Under some environmental conditions, the insulation resistance value will decrease unnecessarily. In addition, pay attention to the experimental voltage value of the insulation resistance. Depending on the insulation resistance (MΩ) = the voltage applied to the insulator (V)/leakage current (μA), different voltages are applied, and there are different results. In the experiment of aviation plug, the applied voltage is generally 10V, 100V and 500V.
2: withstand voltage
The withstand voltage is the threshold voltage that can be accepted between the insulating parts of the touch pair or between the insulating part and the ground, which is higher than the additional voltage without breakdown in a regular time. It is mainly affected by touch to distance and creepage distance and geometry, insulator material, ambient temperature and humidity, and atmospheric pressure.
3: Combustibility
Any aviation plug is inseparable from the current during operation, which has the risk of fire. Therefore, the aviation plug is required not only to avoid ignition, but also to self-extinguish within a short time once ignition and fire occur. When choosing, pay attention to the selection of air plugs with flame-retardant and self-extinguishing insulating materials.
4: Mechanical parameters
The touch pressure in the aviation plug is an important target, which directly affects the size of the touch resistance and the wear amount of the touch pair. In most configurations, direct measurement of touch pressure is reasonably difficult. Therefore, the touch pressure is often directly measured by the separation force of one foot. For circular pinhole touch pairs, standard pins with regular weights are generally used to check the ability of the female touch piece to hold the weight. Generally, the diameter of the standard pin is -5μm, the lower limit of the diameter of the male touch piece. The total separation force is generally twice the sum of the upper and lower separation forces of one foot. When the total separation force exceeds 50N, it is quite difficult to insert and pull out manually. Of course, for some test equipment or some special requirements, aviation plugs with zero insertion force can be used, and aviation plugs can be automatically dropped off.
5: Mechanical life
The mechanical life of the aviation plug refers to the plugging life, and the general rule is 500 to 1000 times. When reaching the mechanical life of this rule, the touch resistance, insulation resistance and withstand voltage of the aviation plug should not exceed the value of the rule. Strictly speaking, mechanical life is a vague concept. The mechanical life should have a certain relationship with the time. Obviously, the situation is different when it is used up 500 times in 10 years and 500 times in 1 year. It's just that there is no more economical and scientific way to measure it.
6: Number of touch pairs and pinholes
First, the number of touch pairs can be selected according to the needs of the circuit, and at the same time, the volume of the electrical connector and the size of the total separation force must be considered. The larger the number of touch pairs, of course, the larger the volume and the larger the total separation force. In some cases where the reliability requirements are high and the volume is acceptable, the method of connecting two pairs of touch pairs in parallel can be used to improve the reliability of the connection.
In the plugs and sockets of aviation plugs, the pins (male touch pieces) and jacks (female touch pieces) can generally be exchanged for equipment. In practical use, it can be selected according to the live status of both ends of the plug and socket. If the socket needs to be charged frequently, you can choose a socket with a jack. Because the socket with a jack, its live touch parts are buried in the insulator, and it is not easy for the human body to touch the live touch parts, which is relatively safe.
7: Vibration, impact, bump
The first consideration is the electrical continuity of the touch pair when the aviation plug oscillates, impacts, and bumps under the conditions of regular frequency and acceleration. The touch pair is momentarily disconnected under this dynamic stress condition. The regular break times are generally 1μs, 10μs, 100μs, 1ms and 10ms. What should be paid attention to is how to judge the instantaneous failure of the touch pair. Generally speaking, when the voltage drop between the two ends of the closed touch pair (contact) exceeds 50 percent of the power supply electromotive force, it can be concluded that the closed touch pair (contact) is faulty. That is to say, there are two conditions for judging whether an instantaneous interruption occurs: the duration and the voltage drop, both of which are indispensable.
8: Connection method
Aviation plugs are generally composed of plugs and sockets, among which the plug is also called a free end aviation plug, and the socket is also called a fixed aviation plug. The connection and disconnection of the circuit is completed by plugs, sockets, and insertion and separation, so various connection methods of plugs and sockets have occurred. For circular aviation plugs, there are mainly three methods: threaded connection, bayonet connection and marble connection. Among them, the threaded connection is the most common. It has the advantages of simple processing technology, low production cost, and wide application scale, but the connection speed is slow and it is not suitable for occasions requiring frequent insertion and removal and rapid succession. The bayonet-type connection has a faster connection speed due to the longer lead of its three bayonet slots, but it is more complicated to manufacture and the cost is higher. The marble connection is the fastest connection among the three connection methods. It does not require rotary motion, but only needs to perform linear motion to complete the functions of connection, separation and locking. Because it is a direct push-pull connection method, it is only suitable for aviation plugs with low total separation force. Generally, it is more common in small aviation plugs.
9: Equipment method and appearance
The equipment of the aviation plug has front equipment and rear equipment, and the fixing methods of the equipment include rivets, screws, collars or quick locking of the aviation plug itself. There is also a plug and socket that are both free-end aviation plugs, the so-called relay aviation plugs.
10: Environmental parameters
Environmental parameters mainly include ambient temperature, humidity, temperature changes, atmospheric pressure and corrosive environment. The environment in which the electrical connector is used, stored, and transported has a significant impact on its function, so it is necessary to select the corresponding aviation plug according to the actual environmental conditions.
11: Ambient temperature
The metal material and insulating material of the aviation plug determine the working environment temperature of the electrical connector. High temperature will damage the edge material, causing the insulation resistance and withstand voltage performance to decrease; for metals, high temperature can make the touch pair lose elasticity, accelerate oxidation and cause coating deterioration. The general ambient temperature is -55100 degree , and it may be higher in special occasions.
12: Wet
Relative humidity greater than 80 percent is the primary cause of electrical breakdown. The humid environment causes the absorption and dispersion of water vapor on the surface of the insulator, which simply reduces the insulation resistance to below the MΩ level. Long-term exposure to a high-humidity environment will cause physical deformation, differentiation, escape of products, breathing effects, electrolysis, and corrosion. and cracks. Especially for electrical connectors outside the equipment, environmental conditions such as humidity, water infiltration and pollution are often considered. In this case, sealed aviation plugs should be selected. For water-tight and dust-tight electrical connectors, the shell protection level of GB4208 is generally used to indicate.
13: drastic changes in temperature
The humidity drastic change experiment is to simulate the actual operation of using aviation plug equipment to switch from a cold environment to a warm environment, or to simulate the rapid change of the ambient temperature of space vehicles and probes. Sharp changes in temperature may crack or delaminate the insulating material.
14: Atmospheric pressure
At high altitudes where the air is thin, the plastic emits gas, which pollutes the contact pair, increases the tendency of corona generation, reduces the voltage resistance, and causes the circuit to short-circuit. When the altitude reaches a certain value, the performance of the plastic deteriorates. Therefore, when using unsealed aviation plugs at high altitudes, it is necessary to derate them. The recommended voltage derating factors at low air pressure are shown in the table.
15: Corrosive environment
According to the different corrosive environments of aviation plugs, choose aviation plugs with corresponding metal, plastic, and coating structures, such as aviation plugs used in salt spray environments, if there is no anti-corrosion metal surface, the performance will deteriorate rapidly. In the environment with appropriate concentration of SO2, it is not suitable to use the aviation plug with silver-plated touch pair. Mold is also a significant problem in hot flash areas.
16: Termination method
The termination method refers to the connection method between the touch pair of the aviation plug and the wire or cable. Reasonable selection of termination methods and correct use of termination technology are also an important aspect of the use and selection of aviation plugs.
17: Soldering
Soldering is the most common type of soldering. The most important thing for soldering connection is that the continuity of the metal should be formed between the solder material and the surface to be welded. Therefore, for aviation plugs, solderability is important. The most common coatings on the soldered ends of aviation plugs are tin alloys, silver and gold. Reed type touch has solder lug type, punched lug type and notch lug type for common welding ends: pinhole type touch has drilled arc notch type for common welding ends.
18: Crimp
Crimp is a technique for compressing and displacing metal within regulatory limits and connecting wires to a touch pair. A good crimp connection can produce metal mutual fusion flow, so that the wire and the touch pair material are symmetrically deformed. This kind of connection is similar to cold welding connection, which can get better mechanical strength and electrical continuity. It can withstand harsher environmental conditions. It is generally believed that the correct crimp connection is better than soldering, especially in high current applications. Use crimping. When crimping, special crimping pliers or active or semi-active crimping machine must be used. The wire barrel of the touch pair should be correctly selected according to the cross section of the wire. It should be noted that the crimp connection is a permanent connection and can only be used once.
19: Wrap
Winding is to wind the wire directly on the angular touch piece winding post. During winding, the wires are wound under the condition of controlled tension, pressed and fixed at the corners of the winding column of the touch piece to form an airtight touch. There are several requirements for winding the wire: the nominal value of the wire diameter should be within the range of {{0}}.25mm1.0mm; when the wire diameter is not greater than 0.5mm, the elongation of the conductor material is not less than 15 percent ; when the wire diameter is greater than 0.5mm, the conductor The elongation of the material is not less than 20 percent . Winding tools include winding guns and fixed winding machines.
20: Puncture Continuous
Puncture connection, also known as insulation displacement connection, is a novel terminal technology created by the United States in the 1960s. It has the characteristics of high reliability, low cost, and convenient use. It has been widely used in various printed board electrical connectors. It is suitable for the connection of ribbon cables. When connecting, it is not necessary to strip off the insulation layer of the cable, rely on the tip of the "U"-shaped touch reed of the aviation plug to pierce the insulation layer, so that the conductor of the cable slides into the groove of the touch reed and is clamped, so that the A tight electrical connection is formed between the cable conductor and the aviation plug reed. It only requires simple tools, but it is necessary to use cables with regular wire gauges.
21: Screw connection
Screw connection is a connection method using screw terminals. Pay attention to the maximum and minimum cross-sections of the connecting wires and the maximum tightening torque allowed by screws of different specifications.
