CNWe want to make sure the capacity of the inverter matches. First of all, according to the nature of the load, the correct type of inverter is selected.
When selecting a frequency converter, the actual motor current value should be used as the basis for selecting the frequency converter, and the rated power of the motor can only be used as a reference. Secondly, it should be fully considered that the output of the frequency converter contains high-order harmonics, which will cause the power factor and efficiency of the motor to deteriorate.
Voltage matching: The rated voltage of the inverter matches the rated voltage of the motor.
Current matching: For ordinary centrifugal pumps, the rated current of the frequency converter matches the rated current of the motor. For special loads such as deep water pumps, etc., it is necessary to refer to the performance parameters of the motor to determine the current and overload capacity of the inverter in order to require the current. The inverter current setting should not be lower than 1.1 times the rated current of the motor, and the required current is generally set to 1.5 times the rated current of the motor.
One-to-many is a frequency converter with multiple motors. The capacity of the frequency converter is the sum of the capacities of multiple motors (based on the current), which should be enlarged by 10%~15% as much as possible. At the same time, it is necessary to ensure that each motor is properly loaded, how powerful it is and how powerful it is, neither running empty nor overloaded, each performing its duties, cooperating with each other, and coexisting peacefully; but the control is not good, some loads are heavy, and some The load is light, some are exhausted, and some are idle. As a result, the motor with heavy load and overheating burns out, and the whole system is paralyzed, which is not worth the loss. Therefore, be careful when procrastinating for a long time. Then, in turn, drag one more, can't multiple frequency converters carry one motor!
About the cable
If the inverter needs to run with a long cable, measures should be taken to suppress the influence of the long cable on the ground coupling capacitance, so as to avoid insufficient output of the inverter. Therefore, in this case, the capacity of the inverter should be increased by one gear or at the output end of the inverter. Install the output reactor. When the frequency converter is used to control several motors connected 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.
For special applications
1. Such as high ambient temperature, high switching frequency, high altitude, etc., will cause the derating of the inverter at this time, and the inverter needs to be amplified for selection.
2. When using a frequency converter to drive a high-speed motor, due to the small reactance of the high-speed motor, the increase in high-order harmonics will lead to an increase in the output current value. Therefore, the selection of the frequency converter used for high-speed motors has a slightly larger capacity than that of ordinary motors.
3. When driving an explosion-proof motor, the frequency converter has no explosion-proof structure, so the frequency converter should be installed outside the dangerous place.
4. When selecting a frequency converter, be sure to pay attention to whether its protection level matches the situation on site.
other
1. When the frequency converter drives the wound rotor asynchronous motor, most of them use the existing motor. It is easy to cause over-current tripping due to ripple current, so a frequency converter with a slightly larger capacity than usual should be selected.
2. For loads with large torque fluctuations such as compressors and vibrators and peak loads such as oil pressure pumps, you should understand the power frequency operation and choose an inverter with a rated output current greater than the required current.
3. When the frequency converter controls the Roots blower, due to its large starting current, it is necessary to pay attention to whether the capacity of the frequency converter is large enough when selecting the frequency converter.
4. When a frequency converter is used to drive the gear reduction motor, the application range is restricted by the lubrication method of the gear rotating part. Do not exceed the speed allowable value.
5. Single-phase motors are not suitable for inverter drive.
The influence of the distance between the frequency converter and the motor on the system and its measures
In the field of industrial use, the distance between the inverter and the motor installation can be roughly divided into three situations: long-distance, medium-distance and short-distance. Less than 20m is short distance, 20-100m is middle distance, and more than 100m is long distance.
If the distance between the inverter and the motor is within 20m, it can be directly connected to the inverter; for the connection between the inverter and the motor at a medium distance of 20m to 100m, the carrier frequency of the inverter needs to be adjusted to reduce harmonics and interference ; As for the long-distance connection between the inverter and the motor over 100m, not only the carrier frequency must be moderately reduced, but also the output AC reactor must be installed.
