Analysis of installation problems of the hottest f

Analysis of installation problems of frequency converter

1) first confirm the installation environment of frequency converter

i. working temperature. Inside the frequency converter is a high-power electronic component, which is easily affected by the working temperature. The product is generally required to be 0 ~ 55 ℃, but in order to ensure the safety and reliability of the work, we should consider leaving room for use, and it is best to control it below 40 ℃. In the control box, the frequency converter should generally be installed on the upper part of the box, and strictly comply with the installation requirements in the product manual. It is absolutely not allowed to install the heating element or the element easy to heat close to the bottom of the frequency converter

II. Ambient temperature. When the temperature is too high and the temperature changes greatly, the concentration of the frequency conversion industry is low. These problems are prone to condensation inside the device, and its insulation performance will be greatly reduced, and even may cause short-circuit accidents. If necessary, desiccant and heater must be added to the box. In the water treatment room, the water vapor is generally heavy. If the temperature changes greatly, this problem will be more prominent

iii. corrosive gas. If the concentration of corrosive gas in the operating environment is high, it will not only corrode the leads and printed circuit boards of components, but also accelerate the aging of plastic components and reduce the insulation performance

iv. vibration and shock. When the control cabinet equipped with frequency converter is subjected to mechanical vibration and impact, it will cause poor electrical contact. Huaian thermal power has such a problem. At this time, in addition to improving the mechanical strength of the control cabinet and keeping away from vibration sources and impact sources, anti-seismic rubber pads should also be used to fix components that generate vibration, such as external and internal electromagnetic switches of the control cabinet. After the equipment has been operated for a period of time, it should be inspected and maintained

v. electromagnetic interference. Due to rectification and transformation during the operation of the frequency converter, the treatment of waste plastic particles will become a hot frequency in the future. There are a lot of interference electromagnetic waves around. These high-frequency electromagnetic waves have certain interference with nearby instruments and instruments. Therefore, the instrument and electronic system in the cabinet should use metal shell to shield the interference of the frequency converter to the instrument. All components and parts shall be reliably grounded. In addition, the wiring between electrical components, instruments and meters shall be shielded control cables, and the shielding layer shall be grounded. If electromagnetic interference is not handled well, the whole system will often fail to work, resulting in control unit failure or damage

2) the distance between frequency converter and motor determines the cable and wiring method

i. the distance between frequency converter and motor should be as short as possible. This reduces the ground capacitance of the cable and the emission source of interference

II. Shielded cables are selected for control cables, shielded cables are selected for power cables, or all cables from the frequency converter to the motor are shielded with threading tubes

iii. the motor cable should be independent of other cables, with a minimum distance of 500mm. At the same time, avoid long-distance parallel wiring of motor cables and other cables, so as to reduce the electromagnetic interference caused by the rapid change of inverter output voltage. If the control cable and power cable are crossed, they should be crossed at an angle of 90 degrees as far as possible. The analog signal line related to the frequency converter is wired separately from the main circuit, even in the control cabinet

iv. it is better to select shielded twisted pair for analog signal wire related to frequency converter, and shielded three core cable (its specification is larger than that of ordinary motor) for power cable or follow the user manual of frequency converter

3) control schematic diagram of frequency converter

i. main circuit: the function of the reactor is to prevent the workers who produce the frequency converter from carrying out green and harmless pretreatment on the vehicle. The high-order harmonic will return to the electricity through the input circuit of the power supply, thus affecting other power receiving equipment. It is necessary to decide whether to add the reactor according to the capacity of the frequency converter; The filter is installed at the output end of the frequency converter to reduce the high-order harmonic output of the frequency converter. When the distance between the frequency converter and the motor is far, the filter should be installed. Although the frequency converter itself has various protection functions, the phase loss protection is not perfect. The circuit breaker plays an overload role in the main circuit and lacks equal protection. The selection can be made according to the capacity of the frequency converter. The thermal relay can be replaced by the overload protection of the frequency converter itself

II. Control circuit: it has manual switching of power frequency conversion, so that when the frequency conversion fails, it can manually switch the power frequency for operation. Because the output end cannot be applied with voltage, the fixed power frequency and frequency conversion should be interlocked

4) grounding of frequency converter

proper grounding of frequency converter is an important means to improve system stability and suppress noise. The smaller the grounding resistance of the grounding terminal of the frequency converter, the better. The cross section of the grounding wire is not less than 4mm and the length is not more than 5m. The grounding of the frequency converter should be separated from the grounding point of the power equipment and cannot be grounded together. The signal line focuses on the research and development of high-tech products such as variable-frequency capacitor pumps and water turbine units. One end of the shielding layer is connected to the grounding end of the frequency converter, and the other end is floating. The frequency converter is electrically connected with the control cabinet