Weidmüller relay 1. Classification of frequency converters
1.1?Inverters are divided into low-voltage inverters (220V and 380V), medium-voltage inverters (660V and 1140V) and high-voltage inverters (3KV, 6KV, 6KV) according to their supply voltage.6KV, 10KV).
1.2?Inverters are divided into constant power inverters, square torque series inverters, simple inverters, general-purpose SE6400 series inverters, elevator-specific inverters, etc. according to their functions.
1.3?Inverters are divided into current type inverters and voltage type inverters according to the nature of the DC power supply..
1.4?According to the output voltage adjustment mode, the inverter is divided into PAM output voltage adjustment mode inverter and PWM output voltage adjustment mode inverter.
1.5?According to the control mode, the inverter is divided into V/F control mode and slip frequency control mode..
1.6?The frequency converter is divided into three types: IGBT, GOT, and BJT according to the main switching device..
1.7?Inverters are divided into plastic case inverters (low power), iron case inverters (mostly medium power), and cabinet inverters (high power) according to their appearance. .
2. Precautions for inverter selection
The inverter can not be used normally under any circumstances, so it is necessary for the user to have more knowledge about the load, environmental requirements and the inverter.
2.1 Load type and selection of frequency converter:
The load driven by the motor is different, and the requirements for the frequency converter are also different.
2.1.1 Fans and pumps are the most common loads: the requirements for frequency converters are the simplest, as long as the capacity of the frequency converter is equal to the capacity of the motor (air compressors, deep water pumps, sediment pumps, fast-changing musical fountains need to increase the capacity).
2.1.2 Crane type load: This type of load is characterized by a large impact when starting, so it requires a certain margin for the frequency converter.At the same time, if you put your elbow under a heavy object, there will be energy feedback, so you must use a braking unit or use a shared bus method.
2.1.3 Uneven load: some loads are sometimes light and sometimes heavy. At this time, the inverter capacity should be selected according to the heavy load, such as rolling mill machinery, crushing machinery, mixer, etc..
2.1.4 large inertial loads: such as centrifuges, punch presses, and rotary kilns in cement plants. These loads have a large inertia, so they may oscillate when starting, and there will be energy back expansion when the motor decelerates?A frequency converter with a larger capacity should be used to speed up the start and avoid oscillation.Cooperate with braking unit to eliminate feedback power.
2.2 Other matters needing attention:
2.2.1 Long-term low-speed rotation, because the motor generates higher heat and the cooling capacity of the fan is reduced, it is necessary to increase the reduction ratio or switch to a 6-level motor to make the motor run near a higher frequency.
2.2.2 The installation location of the inverter must meet the requirements of the standard environment, otherwise it will easily cause failure or shorten the service life; the distance between the inverter and the drive motor is generally not more than 50 meters, if a longer distance is required, the carrier frequency must be reduced or the output must be increased Reactor option can work normally.
3. Precautions for the use of the inverter
3.1 physical environment
3.1.1 working temperature.There are high-power electronic components inside the inverter, which are easily affected by the operating temperature. The product generally requires 0~55℃, but in order to ensure safe and reliable work, you should consider leaving room when using it, and it is best to control it below 40℃.In the control box, the installation of the inverter should strictly comply with the installation requirements in the product manual, and it is absolutely not allowed to install heating elements or components that are prone to heat close to the bottom of the inverter..
3.1.2 ambient temperature.When the temperature is too high and the temperature changes greatly, condensation is likely to occur inside the inverter, and its insulation performance will be greatly reduced, and it may even cause a short circuit accident..When necessary, desiccant and heater must be added to the box.
3.1.3 Corrosive gas.If the concentration of corrosive gas is high in the use environment, it will not only corrode the leads of the components, printed circuit boards, etc., but also accelerate the aging of the plastic devices and reduce the insulation performance. In this case, the control box should be made into a closed structure , And ventilate.
3.1.4 Vibration and shock.When the control cabinet equipped with the inverter is subjected to mechanical vibration and impact, it will cause poor electrical contact.At this time, in addition to improving the mechanical strength of the control cabinet and staying away from the source of vibration and impact, vibration-proof rubber pads should also be used to fix the vibration-generating components such as electromagnetic switches outside and inside the control cabinet..After the equipment has been running for a period of time, it should be inspected and maintained.
3.2 Electrical environment
3.2.1 Prevent electromagnetic interference.Due to the rectification and frequency conversion of the inverter during operation, a lot of interference electromagnetic waves are generated around, and these high-frequency electromagnetic waves have certain interference to nearby instruments and instruments..Therefore, the instrument and electronic system in the cabinet should use metal casing to shield the interference of the inverter to the instrument.All components should be reliably grounded. In addition, shielded control cables should be used for the wiring between electrical components, instruments and meters, and the shielding layer should be grounded.If electromagnetic interference is not handled well, the entire system will often fail to work, leading to failure or damage to the control unit.
3.2.2 Prevent overvoltage at the input.The input terminal of the inverter power supply is often protected against overvoltage, but if the high voltage at the input terminal lasts for a long time, the input terminal of the inverter will be damaged..Therefore, in actual application, it is necessary to verify the input voltage of the inverter, single-phase or three-phase and the rated voltage of the inverter.Especially when the power supply voltage is extremely unstable, there must be a voltage regulator device, otherwise it will cause serious consequences.
Three, ground
The correct grounding of the inverter is an important means to improve the sensitivity of the control system and suppress noise. The smaller the grounding resistance of the inverter grounding terminal E (G), the better, the cross-sectional area of the grounding wire should not be less than 2mm2, and the length should be controlled within 20m.The grounding of the inverter must be separated from the grounding point of the power equipment, and cannot be grounded together.The shielding layer of the signal input line should be connected to E(G), and the other end must not be connected to the ground, otherwise it will cause the signal to fluctuate and cause the system to oscillate..There should be electrical connection between the inverter and the control cabinet. If the actual installation is difficult, a copper core wire can be used for jumper connection..
Four, lightning protection
In the frequency converter, there is generally a lightning absorption network, which mainly prevents the intrusion of instant lightning and damages the frequency converter.However, in actual work, especially when the power cord is introduced overhead, the absorption network of the frequency converter alone cannot meet the requirements..This problem is particularly important in areas where lightning is active. If the power supply is overhead incoming lines, install a special frequency conversion arrester (optional) at the incoming line, or pre-bury steel pipes 20m away from the inverter for special grounding as required by the specification. protection.If the power supply is introduced by a cable, a lightning protection system in the control room should be prepared to prevent lightning from entering and destroying the equipment.Practice has shown that it can basically solve the problem of lightning strikes effectively.Weidmüller Relay
Introduction of frequency converter Weidmüller relay
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