Methods for extending the service life of inverters - LS generates electricity

1. The influence of electromagnetic disturbance on the inverter:

In the modern industrial control system, the microcomputer or PLC control technology is mostly selected, and in the process of system planning or transformation, it is necessary to pay attention to the disturbance of the inverter to the microcomputer control board. The inverter is disturbed by the outside world, because the general process level of the microcomputer control board planned by the user is poor, and it does not meet the EMC international standards.

1) Good grounding. It is necessary to ground the grounding wire of the strong current control system such as the motor through the grounding bus, and the shielding ground of the microcomputer control board should be grounded separately. For some situations where the disturbance is severe, it is advocated to connect the sensor, I/0 interface shield and the control ground of the control panel.

2) Install EMI filters, common-mode inductors, high-frequency magnetic rings, etc. to the input power supply of the microcomputer control board, which can effectively press and conduct disturbances. In addition, in the case of severe radiation disturbance, such as the presence of GSM or PHS base stations, a metal mesh shield can be added to the microcomputer control board for shielding.

3) Install an EMI filter at the input end of the inverter, which can effectively press the conduction disturbance of the inverter to the power grid, and install input communication and DC reactor, which can improve the power factor, reduce harmonic pollution, and have a good inductive effect. In some cases where the distance between the motor and the inverter exceeds 100 m, it is necessary to add a communication output reactor on the inverter side to solve the leakage current protection caused by the dispersion parameters of the output wire to the ground and reduce the external radiation disturbance. A useful way is to choose the method of steel pipe threading or shielding cable, and firmly connect the steel pipe shell or cable shield with the earth. It is worth noting that when the communication output reactor is not increased, if the method of steel pipe threading or shielding cable is selected, the dispersion capacitance of the output to ground is increased, and the overcurrent is simply presented. Of course, one or several of these methods are generally adopted in practice.

4) Electrically shielding and blocking the analog sensor detection input and imitation control signal. In the planning process of the control system composed of frequency converters, it is advocated that imitation control should not be used as much as possible, especially when the control interval is greater than 1m and the control cabinet device is crossed. Because the inverter generally has multi-stage speed setting, switching frequency input and output, which can meet the requirements. If you have to use analog control, it is recommended that you must use a shielded cable and complete a remote grounding on the sensor side or the inverter side. If the disturbance is still severe, the DC/DC barrier method needs to be completed. It is possible to choose a standard DC/DC module, or choose a v/f conversion optical block, and then choose the frequency setting input.

Methods for extending the service life of inverters - LS generates electricity

Methods for extending the service life of inverters - LS generates electricity

2. Influence of the working environment:

In the practical application of LS inverter, because most of the domestic customers have special computer rooms, in order to reduce the cost, most of them directly install LS inverter on the industrial site. The job site generally has the problems of large dust, high temperature, high humidity, as well as metal dust, corrosive gases and so on in aluminum occupations. Therefore, it is necessary to take appropriate measures according to the situation on site.

1) The inverter should be installed inside the control cabinet.

2) The inverter is well installed in the middle of the control cabinet; The inverter should be straightened, and the large components that may block the exhaust and air intake should be avoided directly above and below.

3) The small distance between the top and bottom of the control cabinet between the upper and lower marginal parts of the inverter, the partition, or the large elements that may be necessary for the device should be greater than 300 mm.

4) If special users need to remove the keyboard in use, the keyboard hole of the inverter panel must be tightly sealed with tape or replaced by a fake panel to avoid a large amount of dust entering the inverter.

5) When using the inverter in dusty places, especially in places with multi-metal dust and flocculents, the overall control cabinet is required to be sealed, and the air inlet and outlet are specially planned for ventilation; There should be a protective net and a protective top cover air outlet on the top of the control cabinet; The bottom of the control cabinet should have a base plate, air inlet, wire inlet holes, and a dust filter.

6) Most of the inverter manufacturers' internal printed boards and metal structural parts are not specially treated to prevent wetting and mildew, and if the inverter is in a harsh operating environment for a long time, the metal structural parts are simply corroded. Under the condition of high temperature operation, the conductive copper bar will be more corroded, and the fine copper wires on the microcomputer control board and the drive power board will be damaged by corrosion. Therefore, it is necessary to have basic requirements for the internal planning of the inverter used in the case of wetting and containing corrosive gases, such as the printed circuit board must be treated with conformal coating, and the structural parts must be treated with nickel-chromium plating. In addition, it is also necessary to adopt other positive, useful and reasonable methods to prevent wetting and corrosive gases.

3. The influence of power grid quality on the inverter:

In the case of impact loads such as electric welding machines, electric arc furnaces, rolling mills, etc., the voltage often shows flicker; In a workshop, there are multiple inverters and other capacitive rectifier loads during operation, and the harmonics generated by them have a very serious pollution on the quality of the power grid, and also have a proper destructive effect on the equipment itself. The following methods can be adopted.

1) In the case of impact loads such as electric welding machines, electric arc furnaces, rolling mills, etc., it is advocated that users increase reactive power static compensation devices to improve the power factor and quality of the power grid.

2) In the workshop where the inverter is more concentrated, it is advocated to choose the convergent rectification and DC common bus power supply mode. It is recommended that the user choose the 12-pulse rectification mode. The advantage is that the harmonics are small and energy-saving, especially suitable for frequent starting, braking, and the motor is in the occasion of both electric operation and power generation operation.

3) A passive LC filter is installed on the input side of the inverter to reduce the input harmonics, improve the power factor, have high reliability and good function.

4) The input side of the inverter is equipped with an active PFC device, which has a good effect but a high cost.

Methods for extending the service life of inverters - LS generates electricity

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