1. Select the inverter according to the load characteristics
A: Fans and pumps are the most common loads: the requirements for the inverter are the simplest, as long as the inverter capacity is equal to the capacity of the motor (air compressors, deep water pumps, sediment pumps, and fast-changing music fountains need to increase their capacity).
B: Crane load: This type of load is characterized by a large impact when starting, so the inverter is required to have a certain margin. At the same time, when the elbow is placed under the heavy object, there will be energy feedback, so it is necessary to use a braking unit or use a common bus method.
C: 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.
d: Large inertia load: such as centrifuge, punch, rotary kiln of cement plant, this kind of load inertia is very large, so it may oscillate when starting, and there is energy feedback when the motor decelerates. A slightly larger inverter should be used to speed up start-up and avoid oscillation. Cooperate with the braking unit to eliminate the regenerative energy.
2. When selecting the inverter, the actual motor current value should be used as the basis for the selection of the inverter, and the rated power of the motor can only be used as a reference. In addition, it should be fully considered that the output of the inverter contains abundant high-order harmonics, which will make the power factor and efficiency of the motor deteriorate. Therefore, compared with the power supply to the motor with an inverter, the current of the motor will increase by 10% and the temperature rise will increase by about 20%. Therefore, when selecting motors and inverters, this situation should be taken into account and appropriate margins should be left to prevent the temperature rise from being too high and affecting the service life of the motor.
3. Long-term low-speed rotation, due to the high calorific value of the motor and the reduction of the cooling capacity of the fan, it is necessary to increase the reduction ratio or change to a 6-stage motor to make the motor run near a higher frequency.
4. For some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., it will cause the derating of the inverter, and the inverter needs to be enlarged by one gear.
5. The installation site of the inverter must meet the requirements of the standard environment, otherwise it is easy to cause failure or shorten the service life; The distance between the inverter and the drive motor is generally no more than 50 meters, and longer distances require a reduction in the carrier frequency or an increase in the output reactor option for proper operation.
6. When the inverter wants to run with a long cable, measures should be taken to suppress the influence of the long cable on the ground coupling capacitance to avoid insufficient output of the inverter. Therefore, the inverter should be amplified by one or two gears, or the output reactor should be installed at the output end of the inverter.
7. When using the inverter to control the high-speed motor, due to the small reactance of the high-speed motor, more high-order harmonics will be generated. These higher harmonics will increase the output current value of the inverter. Therefore, when choosing an inverter for a high-speed motor, it should be slightly larger than the inverter for a normal motor.
8. When the inverter is used in a pole-changing motor, full attention should be paid to selecting the capacity of the inverter, so that its maximum rated current is below the rated output current of the inverter. In addition, when the number of poles is converted in operation, the motor should be stopped first, otherwise it will cause the motor to run idle, and the inverter will be damaged when it is bad.
9. When driving the explosion-proof motor, the inverter does not have an explosion-proof structure, and the inverter should be set outside the dangerous place.
10. When the inverter is used to drive the gear reducer motor, the scope of use is restricted by the lubrication mode of the rotating part of the gear. When lubricating oil, there is no limit in the low-speed range; In the high-speed range above the rated speed, there is a risk that the lubricant will run out. Therefore, do not exceed the maximum speed tolerance.
11. When the inverter drives the winding rotor asynchronous motor, because the winding motor has a small impedance of the winding motor compared with the ordinary squirrel cage motor, it is easy to overcurrent tripping caused by ripple current, so the inverter with a slightly larger capacity than usual should be selected.
12. When the inverter drives the synchronous motor, the output capacity will be reduced by 10%-20% compared with the power frequency power supply, and the continuous output current of the inverter is greater than the product of the rated current of the synchronous motor and the standard unit value of the synchronous intake current.
13. In the case of loads with large torque fluctuations such as compressors and vibrating machines and peak loads such as hydraulic pumps, if the inverter is selected according to the rated current or power value of the motor, the phenomenon of overcurrent protection due to peak current may occur. Therefore, it is necessary to understand the operation of the power frequency and choose an inverter with a rated output current that is larger than its maximum current.
14. When the frequency converter drives the submersible pump motor, because the rated current of the submersible pump motor is larger than the rated current of the ordinary motor, the rated current of the frequency converter is greater than the rated current of the submersible pump motor.
15. When the inverter controls the roots fan or special fan, due to its large starting current, it is necessary to pay attention to whether the capacity of the inverter is large enough when choosing the inverter.
16. When choosing an inverter, you must pay attention to whether its protection level matches the situation on site. Otherwise, the dust and water vapor on site will affect the long-term operation of the inverter.
17. Single-phase motors are not suitable for inverter drive.
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