How to carry out the selection of inverter normally, is the difficulty faced by many enterprise technical personnel and business personnel, in addition, the selection of the inverter body alone, without considering whether the inverter selection and capacity matching is appropriate, is also unscientific.
So what exactly to do?
1. Select the inverter according to the load characteristics.
Second, when selecting the inverter, the current value of the practical motor should be used as the basis for the selection of the inverter, and the additional power of the motor can only be used as a reference. Secondly, it should be fully considered that the output of the inverter contains higher harmonics, which will form the power factor and power of the motor will deteriorate.
3. When the inverter wants to run with a long cable, the inverter should be enlarged by one gear or the output reactor should be installed at the output end of the inverter.
4. When the inverter is used to control several motors connected in parallel, it must be considered that the sum of the length of the cable from the inverter to the motor is within the allowable range of the inverter.
5. For some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., it will cause the capacity reduction of the inverter, and the inverter needs to be expanded by one gear.
6. When selecting the inverter for high-speed motors, it should be slightly larger than the inverter of general motors.
7. When the inverter is used in the pole changing motor, the capacity of the inverter should be selected so that the maximum additional current is below the additional output current of the inverter.
8. 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.
9. 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. Do not exceed the maximum speed tolerance.
10. When the inverter drives the wound rotor asynchronous motor, most of the existing motors are used. It is easy to overcurrent tripping due to ripple current, so it is necessary to select an inverter with a slightly larger capacity than usual.
11. When the inverter drives the synchronous motor, the output capacity is reduced by 10%-20% compared with the power frequency power supply.
12. For compressors, vibrators and other loads with large torque fluctuations and hydraulic pumps and other peak loads, the power frequency operation status should be understood, and the inverter with additional output current greater than its maximum current should be selected.
13. When the inverter controls the roots fan, because its starting current is very large, we must pay attention to whether the capacity of the inverter is large enough when selecting the inverter.
14. When selecting the inverter, we must pay attention to whether its protection level matches the situation on site.
15. Single-phase motors are not suitable for inverter drive.
If there is only the high reliability of the inverter body, and the inverter selection and capacity matching are not appropriate, the frequency conversion speed regulation system composed of it cannot achieve high reliability, or even unable to operate, so how to ensure the normal and efficient operation of the frequency conversion adjustment system?
We want to make sure that the capacity of the inverter is matched. First of all, according to the nature of the load, the correct type of inverter is selected. The general criterion is what the nature of the load characteristics with what characteristics of the inverter.
(1) Constant torque production equipment - within the speed regulation range, the load torque is basically constant. A frequency converter with constant torque function should be selected. It can only be overloaded to maintain 150% additional current for 1 minute.
(2) Square torque production equipment - within the speed regulation range, the load torque is proportional to the square of the speed, that is, M∝n2, centrifugal fan, water pump is its typical representative. The inverter with M∝n2 characteristics can have a small overload, and the additional current of 110%-120% is overloaded for 1 minute.
(3) Constant power load production equipment - within the speed regulation range, the speed is low and the torque is large; The rotational speed is high and the torque is small. Typical equipment such as machine tools and winding weaves.
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