What is the principle of the explosion-proof positive pressure cabinet?
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Principle of explosion protection:
1. Positive pressure explosion-proof is a special type of explosion-proof type. Its main guiding ideology is to isolate the flammable substance from the ignition source to achieve the purpose of explosion-proof. The method is realized by matching the control system in the explosion-proof control box with the pneumatic system, introducing the shielding gas from the safe area into the positive pressure chamber, and after thoroughly cleaning and replacing the combustible gas in the positive pressure chamber, A certain pressure is maintained in the pressure chamber to prevent the entry of flammable gases and conductive dust from an external hazardous environment, thereby achieving the purpose of explosion protection.
2. According to the pressure holding mode in the positive pressure chamber, it can be mainly divided into positive pressure with dilution airflow and positive pressure with leakage compensation.
3. The positive pressure with the dilution gas flow is continuously flowing through the positive pressure chamber by the shielding gas, and maintains a certain flow rate, so that the pressure of the positive pressure chamber is maintained within the working pressure range, and the gas of the positive pressure chamber can be continuously cleaned and Replacement. Since the shielding gas continuously flows through the positive pressure chamber, it can take away the heat generated by the operation of the internal components while achieving the explosion-proof requirements, so it is more suitable for installing some electrical components or equipment with a large amount of heat, such as a frequency converter and a soft device. Starter, high power thyristor, motor, etc. The downside is that the required air flow is large, and the user's on-site air supply needs to provide sufficient flow and pressure.
4. The positive pressure with leakage compensation is that the control system detects the pressure of the positive pressure chamber in real time, and controls the inflow and outflow of the protective gas through the electromagnetic valve. When the pressure in the positive pressure chamber is too low, open the intake solenoid valve to make the pressure rise to the working pressure range; when the positive pressure chamber pressure is too high, open the exhaust solenoid valve to exhaust the pressure to the working pressure range. Inside. Since the shielding gas does not continuously flow, the positive pressure housing with leakage compensation is suitable for installing low-voltage electrical components with low heat generation, such as various electrical control systems.
5. According to the requirements of national standards, the positive pressure type explosion-proof control cabinet must also have interlocking and alarm functions. That is, when the positive pressure chamber ventilation process is not completed or the positive pressure chamber pressure does not reach the working pressure range, the positive pressure chamber cannot be powered to ensure safety. When the pressure in the positive pressure chamber under operation is lower than the lower limit or upper limit of the set alarm pressure, the control system takes adjustment measures, and an audible and visual alarm device is alerted to the user. When the adjustment measures taken by the control system are invalid and the pressure continues to decrease or rise to the lower limit or upper limit of the set power cut-off pressure, the system should cut off the positive pressure chamber power supply and stop the operation.
From the above situation, the idea of ​​positive pressure type explosion-proof power distribution cabinet is different from other explosion-proof type. Under the condition that the pressure and flow rate of control system and shielding gas are reasonable, the size design of positive pressure chamber is more flexible and can be produced. The larger size of the product, and the built-in electrical components and equipment can be installed according to user requirements or installed by the user, greatly enhancing the scalability of the user.

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