There are many kinds of frequency converters, and we often don't know how to choose them. What should we pay attention to in the selection of frequency converters? Let's take a look at it together. We need to ensure that the capacity of the frequency converter matches. First of all, choose the correct type of frequency converter according to the nature of the load.

When selecting frequency converter, we should take the actual motor current value as the basis for selecting frequency converter, and the rated power of 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 frequency converter is consistent with the rated voltage of the motor.

Current matching: for ordinary centrifugal pumps, the rated current of the frequency converter is consistent with the rated current of the motor. For special loads such as deep-water pumps, it is necessary to refer to the motor performance parameters to determine the inverter current and overload capacity with the maximum current. The current setting of the frequency converter shall not be less than 1.1 times the rated current of the motor, and the maximum current is generally set to 1.5 times the rated current of the motor.

About one drag more. One driving many means one frequency converter with multiple motors. The capacity of the frequency converter is the sum of the capacities of multiple motors (based on the current), and it is better to enlarge it by 10% - 15%. At the same time, it is necessary to ensure that each motor carries the appropriate load, works as hard as it can, neither idles nor overloads, performs its own duties, cooperates with each other, and coexists peacefully; But the control is not good. Some are heavily loaded, some are light loaded, some are tired and some are idle. As a result, the motor with heavy load is heated and burned, and the whole system is paralyzed, which is not worth the loss. Therefore, be careful when dragging on for a long time.

Then, on the contrary, how about dragging more than one frequency converter with one motor? Answer: absolutely prohibited.

About cables

If the frequency converter wants to run with a long cable, measures should be taken to suppress the influence of the long cable on the ground coupling capacitance at this time to avoid insufficient output of the frequency converter. Therefore, in this case, the capacity of the frequency converter should be amplified by one gear or an output reactor should be installed at the output end of the frequency converter. When the frequency converter is used to control several motors in parallel, it must be considered that the total length of the cable from the frequency converter to the motor is within the allowable range of the frequency converter.

About special applications

1. Such as high ambient temperature, high switching frequency, high altitude, etc., at this time, it will cause the capacity reduction of the frequency converter, and the frequency converter needs to enlarge the first gear selection.

2. When using a frequency converter to drive a high-speed motor, the output current increases due to the small reactance of the high-speed motor and the increase of high-order harmonics. Therefore, the capacity of frequency converter used in high-speed motor selection is slightly larger than that of ordinary motor selection.

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

4. When selecting a frequency converter, you must pay attention to whether its protection level matches the situation on site.

other

1. When the frequency converter drives the wound rotor asynchronous motor, it mostly uses the existing motor. Over current tripping caused by ripple current is easy to occur, so frequency converter with slightly larger capacity should be selected.

2. For loads with large torque fluctuations such as compressors and vibrators and peak loads such as oil pumps, it is necessary to understand the power frequency operation and select a frequency converter with a rated output current greater than its maximum current.

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

4. When using the frequency converter to drive the gear reduction motor, the scope of use is restricted by the lubrication mode of the gear rotating part. Do not exceed the allowable maximum speed.

5. Single phase motor is not suitable for frequency converter drive.

In the industrial use site, the installation distance between the frequency converter and the motor can be roughly divided into three situations: long distance, medium distance and short distance. Within 20m is short distance, 20-100m is medium distance, and above 100m is long distance.

If the distance between the frequency converter and the motor is within 20m, it can be directly connected with the frequency converter;

For the medium distance connection between the frequency converter and the motor of 20m to 100m, it is necessary to adjust the carrier frequency of the frequency converter to reduce harmonics and interference; For the long-distance connection between the frequency converter and the motor of more than 100m, not only the carrier frequency should be appropriately reduced, but also the output AC reactor should be installed.