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Performance and Countermeasures of Capacitor in High Temperature Environment
2024/06/19
Fundamentals of 1. Capacitance
A capacitor is an element that stores electrical charge and is usually composed of an insulating material between two conductive plates. When a voltage is applied across the capacitor, the capacitor will store charge and form a certain electric field force line. The main performance indicators of capacitors include capacitance, interpolar voltage, dielectric loss, and so on.
2. high temperature influence mechanism
In the high temperature environment, the electrical properties of the capacitor will be greatly affected, mainly in the following aspects:
1. Change in capacitance: High temperature will increase the resistance of the capacitor conductor plate, which in turn will cause the capacitance of the capacitor to decrease.
2. Capacity drift: Under high temperature environment, the medium of the capacitor will undergo thermal expansion, which will cause the plate spacing and plate area to change, resulting in its capacity drift.
3. Temperature coefficient change: The electrical properties of the capacitor are not only affected by high temperature, but also affected by the temperature coefficient. At high temperatures, the temperature coefficient changes, causing the capacitor capacitance to drift.
3. response measures
In order to reduce the influence of high temperature on the electrical properties of capacitors, the following measures can be taken:
1. Select the appropriate dielectric material: select the dielectric material with good stability at high temperature as the dielectric of the capacitor.
2. Control of high temperature environment: for capacitors in high temperature environment, cooling measures can be taken or ventilation can be increased to reduce the ambient temperature.
3. Take protective measures: such as limiting the maximum voltage, ensuring the board spacing, installing insurance, etc., to protect the performance of the capacitor from damage.
Summary: In high temperature environment, the electrical performance of the capacitor is easily affected, resulting in the capacitance change of the capacitor, temperature drift and other problems. In order to ensure the normal use of the capacitor, we should choose the appropriate dielectric material, control the high temperature environment, take protective measures and other means.
Influence of High Temperature on Capacitor and Fault Performance
2024/06/19
Capacitor is a common component in the circuit, it has the ability to store charge and release charge. However, in a high temperature environment, the performance of the capacitor may be affected to a certain extent, mainly in the following aspects:
1. Lower the capacitance value
In a high temperature environment, the dielectric of the capacitor may decompose due to heat, resulting in a decrease in the capacitance value. This situation is more likely to occur in capacitors with poor high temperature resistance.
2. Increase leakage current
Under high temperature environment, the leakage current of the capacitor may increase, which is due to the properties of the dielectric affected by thermodynamic factors. The increase of leakage current will reduce the stability of the circuit and affect the normal operation of the circuit.
3. Increase ESR
ESR(Equivalent Series Resistance) is the internal resistance of the capacitor. It refers to the electric power generated inside the capacitor when the capacitor is energized. Because the current has many factors affecting the impedance, the ESR of the capacitor usually increases in high temperature environment, which will lead to the decline of the performance of the capacitor and affect the normal operation of the circuit.
Operating temperature of high temperature capacitors
2024/06/19
-40 ℃ to 125 ℃
The normal operating temperature range for high temperature capacitors is -40°C to 125°C. 1
High temperature capacitors are designed to maintain stable operating performance in high temperature environments. Different types of capacitors have different heat resistance properties, and some of them are able to operate under extreme high temperature conditions. For example, benzyl silicone oil impregnated film paper composite dielectric capacitors can operate normally in a temperature environment of -40°C to 125°C. This capacitor uses heat-resistant polyester film and silicone oil as key materials, enabling it to function for a long time under high temperature conditions.
In addition, the metalized polypropylene film dry capacitor is also a high temperature capacitor, its operating temperature range is -55 ℃ to 125 ℃, long-term operation of the operating temperature of 105 ℃. This kind of capacitor adopts high temperature resistant polypropylene film, which can increase the upper limit of the operating temperature of the capacitor, so as to adapt to a wider range of high temperature working environment.
In general, the design and material selection of high-temperature capacitors enable them to maintain stable working performance in high-temperature environments, and their operating temperature range usually covers a wide range from low temperature to high temperature to meet the needs of different application scenarios.
The function and application of lead capacitor
2022/07/28
Lead capacitor is a kind of capacitor, mainly composed of two metal plates and a layer of insulating material, one of which is connected to the positive electrode of the circuit (called the positive plate), and the other side is connected to the negative electrode (called the negative plate). Lead capacitor mainly has the following several functions:
The difference between thermistor and ordinary resistor
2021/11/12
The main difference between thermistors and ordinary resistors is their sensitivity to temperature. The resistance value of ordinary resistors has been determined at the time of manufacture and will not change with temperature changes during operation. Its working principle is based on the resistance effect of conductor materials. A thermistor is a sensor resistor whose resistance value changes with temperature. Thermistors are divided into positive temperature coefficient (PTC) and negative temperature coefficient (NTC). The resistance value of the former increases with the increase of temperature, and the resistance value of the latter decreases with the increase of temperature. The working principle of the thermistor is based on the thermal characteristics of the semiconductor material, that is, when the temperature changes, the carrier concentration of the semiconductor will change, which will cause the change of the resistance value. 12
In addition, the performance parameters and application scenarios of thermistors and ordinary resistors are also different. The main performance parameters of ordinary resistors include resistance, tolerance, temperature coefficient, etc., with good stability, and are widely used in various electronic devices as circuit components such as current limiting, voltage division, and sampling. The main performance parameters of thermistors include temperature measurement range, sensitivity, tolerance, etc. Due to the characteristics of resistance changing with temperature, they are widely used in temperature detection, control and compensation scenarios.
In general, a thermistor is a temperature-sensitive resistor whose resistance changes with temperature, and has good sensitivity but relatively poor stability; while an ordinary resistor is a fixed resistor whose resistance The value will not change with temperature changes during work, and the stability is better.
2022/01/10
Lead capacitor is the capacitor has two lead wires, which are plugged into the hole of the circuit board for welding when in use. The difference with SMD capacitor is: SMD electric heating itself without lead, directly mounted on the circuit board.
Capacitors, often referred to as capacitance for its ability to accommodate charge, are represented by the letter C. Definition 1: Capacitor, as the name suggests, is a 'container with charge', which is a device that holds electric charge. English name: capacitor. Capacitor is one of the electronic components widely used in electronic equipment, which is widely used in the circuit of the isolation, coupling, bypass, filtering, tuning circuit, energy conversion, control and so on. Definition 2: Capacitor, any two insulated and closely spaced conductors (including wires) form a capacitor.
The working principle of thermistor
2021/11/12
A thermistor is a sensor resistor whose resistance value changes with temperature. According to the temperature coefficient is divided into positive temperature coefficient thermistor (PTC thermistor, that is, Positive Temperature Coefficient thermistor) and negative temperature coefficient thermistor (NTC thermistor, that is, Negative Temperature Coefficient thermistor). The resistance value of the positive temperature coefficient thermistor increases with the increase of temperature, and the resistance value of the negative temperature coefficient thermistor decreases with the increase of temperature, which belong to the semiconductor device.
The difference between safety capacitor and ordinary capacitor
2021/11/12
The main difference between safety capacitors and ordinary capacitors lies in their design purpose, certification requirements, materials used, safety performance and applications.
Design purpose and function: safety capacitor is mainly used to ensure that the capacitor will not cause electric shock after failure, does not endanger personal safety, mainly used in anti-interference circuit filtering effect. They are used in the power filter, play the role of power filter, respectively, the common mode, differential mode interference from the filter. For safety and EMC considerations, it is generally recommended to add safety capacitors to the power inlet. The ordinary capacitor is used for general power or high-frequency entertainment electronic devices, the main role is to carry out voltage regulation and frequency conversion.
Certification requirements: safety capacitors generally have to pass many certifications, such as CQC, VDE, UL, CUL, etc., and the more certifications, the better. Ordinary CBB capacitors do not require any certification.
Materials used: The materials used in safety capacitors are usually metallized polypropylene films, while metal foils or aluminum foils are used as electrode materials in ordinary capacitors. In addition, the safety capacitor also has a higher voltage level and lower leakage current, making it more reliable and safe in high temperature, high voltage and high frequency environments.
Safety performance: The safety capacitor will not retain the charge after the external power supply is disconnected, so it will not produce electric shock, which is a major difference from ordinary capacitors. Ordinary capacitors will retain the charge for a long time after the external power supply is disconnected, and will be electrified if touched by hand.
Application: safety capacitor is mainly suitable for power supply of electronic instruments and electronic equipment, used in switches, contacts and other parts of the spark discharge, can play a role in absorbing pulse interference and reducing electromagnetic disturbance. Ordinary capacitors are widely used in various types of electronic equipment, differential motors, power tools, lighting fixtures, air conditioners, refrigerators, washing machines and other household appliances and power systems.
To sum up, the safety capacitor is a kind of electronic device with high safety performance, and its design and use of materials are aimed at improving the safety and stability of the circuit, while the ordinary capacitor is more focused on the realization of the basic functions of the circuit.
What are the characteristics of thermistor
2021/11/09
The main features of thermistors are:
The sensitivity is high, the temperature coefficient of resistance is 10 to 100 times larger than that of metal, and the temperature change of 10-6 ℃ can be detected;
The operating temperature range is wide, normal temperature devices are suitable for -55 ℃ ~ 315 ℃, high temperature devices are suitable for temperatures higher than 315 ℃ (currently up to 2000 ℃), and low temperature devices are suitable for -273 ℃ ~-55 ℃;
The small size, can measure other thermometer can not measure the gap, cavity and biological blood vessels in the temperature;
④ Easy to use, the resistance value can be arbitrarily selected between 0.1 ~ 100kΩ;
⑤ easy to process into complex shapes, can be mass production;
The stability is good, strong overload capacity.
Safety capacitor model parameters
2021/11/09
Safety capacitors, also known as safety capacitors, are mainly used for filtering in anti-interference circuits, especially in power filters, to filter common mode and differential mode interference. They are designed with safety and EMC (electromagnetic compatibility) requirements in mind and are generally recommended for use at the power supply entrance. 12
Safety capacitors are divided into X capacitors and Y capacitors, which are different in connection position and function in the circuit:
The X capacitor is usually connected across the L-G/N-G, and the capacitance value is allowed to be larger than the Y capacitor. However, a safety resistor must be connected in parallel at both ends of the X capacitor to prevent the power cord plug from being charged for a long time due to the charging and discharging process of the capacitor when the power cord is plugged in. The X capacitor must be certified by the safety testing agency and marked with the safety certification mark and the words AC250V or AC275V, but its DC withstand voltage is as high as 2kV or more. X capacitor can be divided into X1, X2 and X3 according to pulse voltage, of which X1 has high voltage resistance greater than 2.5kV and less than or equal to 4kV;X2 high voltage resistance is less than or equal to 2.5kV;X3 high voltage resistance is less than or equal to 1.2kV.
Y capacitors generally appear in pairs, connected between the live wire and the ground wire and the zero wire and the ground wire, effectively filtering out the differential mode signal between 8-10MHz. Y capacitor pay attention to the insulation level, must meet the relevant safety standards, in order to prevent the leakage of electronic equipment or the case is charged. Y capacitors are divided into Y1, Y2, Y3 and Y4 according to the insulation grade.
The model parameters of safety capacitor include capacitance, rated voltage, accuracy, working temperature range, size, etc. For example, Y capacitor has a wide range of capacitance, ranging from 0.1μF to 4700PF. Its rated voltage covers 2000V(2KV) to 500V, with accuracy of 10%, 20%, 5%, etc. Its operating temperature ranges from -25 C to 125 C. Its dimensional parameters such as diameter, thickness and foot distance are also specified.
When choosing the right safety capacitor, you need to consider the specific needs of the circuit, installation space, and safety certification requirements and other factors.
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