In addition, it is unscientific to select the inverter body alone, without considering whether the inverter selection and capacity matching are appropriate.
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 work with a long cable, the inverter should be expanded 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 application occasions, such as high ambient temperature, high switching frequency, high altitude, etc., it will cause the derating of the inverter at this moment, 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 ordinary motors.
7. 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 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 up outside the dangerous place.
9. When the inverter is used to drive the gear reducer motor, the application range is limited by the smooth way of the gear rolling part. 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. In the case of loads with large torque fluctuations such as compressors and vibrating machines and peak loads such as hydraulic pumps, the working conditions of the power frequency 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 blower, 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 is impossible to achieve high reliability, or even unable to work, 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 selection of the type of inverter. The general principle is what 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 for 150% of the additional current to be held 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 mechanisms.
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