First, according to the load characteristics of the selection of inverter
Secondly, the selection of frequency converter should be based on the actual motor current value as the basis of frequency converter selection, and the rated power of the motor can only be used as a reference. Secondly, the output of the inverter should be fully considered to contain high harmonics, which will cause the power factor and efficiency of the motor will be bad.
Thirdly, when the frequency converter is to be operated with long cable, the frequency converter should be enlarged by one grade to choose or output reactor should be installed at the output end of the frequency converter.
Fourth, when the frequency converter is used to control several motors connected in parallel, must consider the length of the frequency converter to the motor of the cable sum in the frequency converter's allowable range.
Fifth, for some special applications, such as high ambient temperature, high switching frequency, high altitude, etc., at this time will cause the inverter capacity reduction, the inverter needs to be enlarged by one grade selection.
Sixth, the choice of inverter for high-speed motor, should be slightly larger than the ordinary motor inverter.
When the inverter is used for variable pole 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.
When driving explosion-proof motor, the inverter has no explosion-proof structure, and the inverter should be set outside the dangerous place.
When the inverter is used to drive a geared motor, the range of use is limited by the lubrication method of the gear rotating part. Do not exceed the maximum permissible speed.
When the inverter drives a wound-rotor asynchronous motor, most of the existing motors are utilized. It is easy to happen over-current tripping phenomenon caused by ripple current, so the inverter with slightly larger capacity than usual should be selected.
XI, inverter drive synchronous motor, compared with the industrial frequency power supply, reduce the output capacity of 10% to 20%.
XII, for compressors, vibration machines and other torque fluctuations in the load and oil pressure pumps and other peak load conditions, should understand the operating conditions of the industrial frequency, choose a frequency converter with a rated output current greater than its maximum current.
Thirteen, when the frequency converter controls the Roots fan, because of its starting current is very large, so when choosing the frequency converter must pay attention to whether the capacity of the frequency converter is large enough.
XIV, when selecting the frequency converter, must pay attention to whether its protection level matches the situation on the site.
Fifteen, single-phase motor is not suitable for inverter drive.
If the high reliability of the inverter body alone, and inverter selection and capacity matching is not appropriate, the composition of the inverter speed control system is not likely to achieve a high degree of reliability, or even unable to operate, then how to ensure that the inverter adjusts the system to operate normally and efficiently?
We have to make sure that the capacity of the frequency converter is matched. First of all, according to the nature of the load, the correct choice of frequency converter type. The general principle is what nature of load characteristics with what characteristics of the inverter.
(1) constant torque production equipment - in the speed range, the load torque is basically constant. Should be selected with constant torque performance inverter. Its overload capacity is 150% of rated current maintained for 1 minute.
(2) square torque production equipment - in the speed range, the load torque is proportional to the square of the rotational speed, that is, M ∝ n2, centrifugal fans, pumps for its typical representative. With M ∝ n2 characteristics of the inverter its overload capacity is small, 110%-120% rated current overload for 1 minute, the
(3) constant power load production equipment - in the speed range, low speed torque; high speed torque is small, that is, M?NC (constant). Typical equipment such as machine tools and winding mechanisms.
