1、 Select frequency converter according to load characteristics

2、 When selecting frequency converter, the actual motor current value should be taken as the basis of frequency converter selection, and the rated power of motor can only be used as reference. Second, the frequency converter and high-order power factor will be considered.

3、 If the frequency converter needs long cable operation, the frequency converter should be enlarged by one gear, or the output reactor should be installed at the output end of the frequency converter.

4、 When the frequency converter is used to control several motors in parallel, it must be considered that the total length of the cables from the frequency converter to the motor is within the allowable range of the frequency converter.

5、 For some special applications, such as high ambient temperature, high switching frequency, high altitude and so on, the converter will reduce the capacity, so the converter should be enlarged by one gear

6、 When selecting the frequency converter for high-speed motor, it should be slightly larger than that of ordinary motor.

7、 When frequency converter is used in pole changing motor, the capacity of frequency converter should be selected to make its maximum rated current below the rated output current of frequency converter.

8、 When driving the explosion-proof motor, the frequency converter has no explosion-proof structure, so the frequency converter should be set outside the dangerous place.

9、 When the frequency converter is used to drive the gear reducer motor, the application range is restricted by the lubrication mode of the gear rotating part. Do not exceed the maximum allowable speed.

10、 When the frequency converter drives the wound rotor asynchronous motor, most of them use the existing motor. It is easy to cause over-current trip due to ripple current, so the frequency converter with larger capacity than usual should be selected..

11、 When the frequency converter drives the synchronous motor, the output capacity is reduced by 10% ~ 20% compared with the power frequency power supply.

12、 For the load with large torque fluctuation such as compressor, vibrator and oil pump with peak load, it is necessary to understand the power frequency operation and select the frequency converter with rated output current greater than its maximum current.

13、 When the frequency converter controls roots blower, due to its large starting current, we must pay attention to whether the capacity of the frequency converter is large enough.

14、 When selecting frequency converter, we must pay attention to whether its protection level matches with the situation on site.

15、 Single phase motor is not suitable for inverter drive.

If there is only a high reliability of the inverter itself, but the selection and capacity matching of the inverter are not appropriate, the frequency conversion speed control system composed of can not achieve high reliability, or even can not operate, then how to ensure the normal and efficient operation of the frequency conversion adjustment system?

We need to make sure that the capacity of the inverter matches. First of all, according to the nature of the load, select the type of inverter correctly. The general principle is what kind of load characteristics with what characteristics of the inverter.

(1) Constant torque production equipment -- in the speed range, the load torque is basically constant. Frequency converter with constant torque performance should be selected. Its overload capacity is 150% of rated current for 1 minute.

(2) Square torque production equipment -- in the speed range, the load torque is directly proportional to the square of the rotational speed, i.e. m ∝ N2, centrifugal fan and water pump are its typical representatives. The frequency converter with m ∝ N2 characteristic has smaller overload capacity, with 110% - 120% rated current overload for 1 minute,

(3) Constant power load production equipment - in the speed range, low speed and high torque; high speed and small torque, i.e. m? NC (constant). Typical equipment such as machine tools and winding mechanism.