How to extend the service life of the inverter

Admin · 1 How to extend the service life of the inverter Wed Aug 12, 2020 12:16 pm

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The frequency converter still has some unsatisfactory places under different operating conditions, resulting in a shortened service life and a corresponding increase in the workload of installation, commissioning, daily maintenance and repair of ancillary equipment, which has caused significant direct and Indirect economic loss. Now the application environment of the inverter, electromagnetic interference and anti-interference, power grid quality and other aspects are analyzed, and the problems that should be paid attention to when using the inverter and the corresponding improvement suggestions are proposed. I believe this will have a significant impact on increasing the service life of the <a href="https://www.vectorque.com/products" rel="noopener noreferrer" target="_blank">inverter</a> effect. 1. The influence of electromagnetic interference on the inverter In modern industrial control systems, computer or PLC control technology is mostly used. In the process of system design or transformation, attention must be paid to the interference of the inverter on the computer control board. The inverter is subject to external interference sources. Due to the poor general technology level of the microcomputer control board designed by the user, it does not comply with EMC international standards. After the inverter is used, the conducted and radiated interference often causes the control system to work abnormally. Describe the necessary measures. 1) Good grounding. The ground wire of the strong electric control system such as the motor must be reliably grounded through the ground bus, and the shielding ground of the microcomputer control board should be grounded separately. For some occasions with severe interference, it is recommended to connect the sensor and I / 0 interface shield to the control ground of the control board. 2) Adding EMI filter, common mode inductance, high frequency magnetic ring, etc. to the input power of the microcomputer control board can effectively suppress conducted interference. In addition, when the radiation interference is serious, such as when there is a GSM or PHS base station around, you can add a metal mesh shield to the microcomputer control board to shield it. 3) Installing an EMI filter on the input end of the inverter can effectively suppress the conduction interference of the inverter to the power grid, and installing input AC and DC reactors can improve the power factor, reduce harmonic pollution, and have a good overall effect. In some occasions where the distance between the motor and the inverter exceeds 100 m, it is necessary to add an AC output reactor on the inverter side to solve the leakage current protection caused by the distribution parameters of the output wire to the ground and reduce the external radiation interference. An effective method is to use steel pipe threading or shielded cable, and connect the steel pipe shell or cable shield to the ground reliably. It is worth noting that when the AC output reactor is not added, if the method of steel pipe threading or shielded cable is used, the distributed capacitance of the output to ground is increased, and overcurrent is prone to occur. Of course, in practice, one or more of these methods are generally adopted. 4) Electrically shield and isolate the analog sensor detection input and analog control signals. In the design process of the control system composed of frequency converters, it is recommended not to use analog control as much as possible, especially when the control distance is greater than 1m and it is installed across the control cabinet. Because the inverter generally has multi-stage speed setting and switching frequency input and output, it can meet the requirements. If it is necessary to use analog control, it is recommended to use shielded cable and achieve a remote grounding on the sensor side or the inverter side. If the interference is still serious, DC / DC isolation measures need to be implemented. You can use standard DC / DC modules, or use optical isolation for v / f conversion, and then use the frequency setting input method. 2. The impact of the working environment In the actual application of frequency converters, most of the domestic customers, except for a few dedicated machine rooms, install the frequency converter directly on the industrial site in order to reduce costs. The work site generally has problems with large dust, high temperature, and high humidity, as well as metal dust and corrosive gases in the aluminum industry. Therefore, it is necessary to make corresponding countermeasures according to the site conditions. 1) The inverter should be installed inside the control cabinet. 2) The inverter is best installed in the middle of the control cabinet; the inverter should be installed vertically, and the large components that may block the exhaust and intake air should be avoided directly above and below the inverter. 3) The minimum distance between the upper and lower edges of the inverter and the top, bottom, or partitions of the control cabinet, or large components that must be installed, should be greater than 300 mm. 4) If a special user needs to remove the keyboard during use, the keyboard hole of the inverter panel must be strictly sealed with tape or replaced with a dummy panel to prevent a large amount of dust from entering the inverter. 5) When using the inverter in a place with many dusts, especially a place with multiple metal dusts and flocs, the overall requirement of the control cabinet is to be sealed, and the air inlet and air outlet are specially designed for ventilation; the top of the control cabinet should have a protective net and protective roof Cover the air outlet; the bottom of the control cabinet should have a bottom plate, air inlets, and wire holes, and install a dust filter. 6) Most of the printed boards and metal structural parts inside the inverter manufacturers have not been specially treated to prevent moisture and mildew. If the inverter is in a harsh working environment for a long time, the metal structural parts are prone to rust. The conductive copper bar will be more corroded during high temperature operation. Corrosion will cause damage to the small copper wires on the computer control board and drive power board. Therefore, for applications that are wet and contain corrosive gases, the internal design of the inverter used must have basic requirements, for example, the printed circuit board must be sprayed with three anti-paints, and the structural parts must be treated with nickel-chromium plating. Craftsmanship. In addition, other positive, effective, and reasonable measures against moisture and corrosion gases are required. 3. The influence of grid quality on the inverter In the case of impact loads such as welding machines, electric arc furnaces, rolling mills, etc., the voltage often flickers; in a workshop, when there are multiple frequency converters and other capacitive rectifying loads working, the harmonics generated by them are very important for the quality of the grid Severe pollution can also cause considerable damage to the equipment itself, ranging from the inability to operate continuously and the damage to the input circuit of the equipment. The following measures can be taken. 1) In the impact load such as electric welding machine, electric arc furnace, rolling mill and other occasions, it is recommended that users add reactive static compensation devices to improve the power factor and quality of the power grid. 2) In workshops where inverters are concentrated, it is recommended to use centralized rectification and DC common bus power supply. It is recommended that users use the 12-pulse rectification mode. The advantage is that the harmonics are small and energy-saving, especially suitable for frequent starting and braking, and the motor is in the occasion of both electric operation and power generation operation. 3) Passive LC filter is installed on the input side of the inverter to reduce input harmonics, improve power factor, high reliability and good effect. 4) The source PFC device is added on the input side of the inverter, which has the best effect but the cost is higher. 4. Conclusion: Starting from the problems that occur in the actual application system of the inverter, from the aspects of external factors such as interference, use environment, power grid quality, etc., the impact of the adverse factors on the inverter in the actual application is proposed, and then the problem is summarized Some methods of solving problems and suggestions for improvement can play a very good role in extending the service life of the inverter, and have certain reference value in the application of actual projects.

How to extend the service life of the inverter

1 How to extend the service life of the inverter Wed Aug 12, 2020 12:16 pm

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