Views: 0 Author: Site Editor Publish Time: 2022-11-04 Origin: Site
In the application of industrial explosion-proof electronic scales, there are always some special environments such as coal mine environment and chemical environment. The special feature of these environments is that there are a lot of flammable and explosive gases in the coal mine environment. In order to ensure the equipment For safety during use and personal safety of construction personnel, electronic scales generally used in these environments need to be certified for explosion-proof, and as an electronic engineer, you need to design reasonably according to the actual environment! In the process of circuit design, what matters should be paid attention to? Below we analyze the principles of several explosion-proof types to let us understand what should be paid attention to! !
1:Analysis of explosion-proof principle of intrinsically safe electronic scale
The heat generated by electric current, sparks and arcs are the main ignition sources that cause explosive gas mixtures to explode. The principle of explosion-proof of intrinsically safe circuit is simply to limit the electronic scale parameters of the circuit or take certain protective measures to achieve the purpose of weakening the thermal effect generated by the current and the discharge energy of sparks and electrodes, so that the circuit system is normal In the working state or in the fault state, the thermal effects and sparks produced cannot ignite the explosive gas mixture.
Focus on the capacitance and inductance of energy storage components. Due to the performance of inductance and current itself, when the device is powered on, the inductance has a hindering effect on the current. When the device is off, the capacitor has a freewheeling effect on the current. When designing the circuit, It is important to analyze the impact of inductance and capacitance on the equipment when the equipment is powered on or off, so that the affected parameters are reduced to a low level: low spark energy, low current energy, small flame, and low temperature.
When power is on, due to the energy storage of the inductance and the discharge of the capacitor when the power is off, the combination of the two greatly increases the intensity of the spark when the device is turned off.
In the design process, it is necessary to clearly select the electronic components used as explosion-proof type, and ensure that the relevant parameters of the circuit are within the specified range. Please check the relevant standards for details, such as the current requirements:
When the voltage is rated, I=(0.45×9-0.7)/(34+10) =76.1mA
When the voltage is the value, I= (0.45×10.8-0.7)/(34+10) =94.5mA
2:Explosion-proof design of explosion-proof electronic scale
The explosion-proof principle of the explosion-proof electronic scale equipment is: the live parts of the electronic weighing scale equipment are placed in a special shell, which has the function of isolating the sparks and arcs generated by the electronic scale components in the shell from the explosive mixture of the shell. And can withstand the explosive pressure generated when the explosive mixture entering the shell is detonated by the sparks and arcs of the electronic scale equipment in the shell, and the shell is not destroyed; at the same time, it can prevent the explosion products from the shell from transferring to the shell outer explosive mixture. , Will not cause the shell to burn and explode. This special enclosure is called "flameproof enclosure". Electronic scale equipment with flameproof enclosure is called "flameproof electronic weighing scale equipment". Explosion-proof electronic weighing scale equipment has good flame-proof and explosion-proof performance, and is widely used in mine underground and other explosive environment workplaces. The mark of the explosion-proof electronic scale equipment is "d".
3:Explosion-proof design of increased safety electronic scale
Increased safety type refers to the electronic equipment that does not produce arcs, sparks or high temperatures that may ignite explosive mixtures under normal operating conditions, and measures are taken to improve safety to avoid these phenomena under normal and approved overload conditions. Scale equipment. In other words, to design an increased safety type, the premise is that the equipment will not produce sparks, arcs or dangerous temperatures during normal operation, and the electronic scale equipment and its components with a rated voltage of not higher than 11kV can be made into an increased safety type.
This explosion-proof structure is suitable for motors, transformers, lighting fixtures and weighing junction boxes. In addition to the intrinsic safety regulations, the increased safety electronic scale equipment must also comply with the relevant regulations of general requirements. It is worth noting that the "increased safety" of the increased-safety type does not mean that it is safer. The increased safety only shows its purpose and has nothing to do with the design itself. The safety of the increased-safety type depends on the performance and operation of the equipment itself. The degree of safety of the environment.